https://orcid.org/0000-0002-8330-1831
Figures
Abstract
Foot structure and function are essential to the health and mobility of giraffe (Giraffa spp.), yet comprehensive evaluations of distal limb pathology remain limited. This retrospective necropsy-based study used postmortem computed tomography (CT) of frozen distal limbs with targeted histopathology to characterize osseous and soft-tissue changes in a historical cohort of giraffe under managed care. Seventy-three distal limbs from 21 giraffe housed at 12 North American zoos (necropsies performed between 2004–2023) were evaluated. Lesions were graded on a scale of 0–3, and localized to either the medial or lateral digits. Findings were summarized at both the animal level (presence in ≥1 digit) and digit level. CT frequently identified multiple distal limb lesions within this necropsy cohort, including pedal osteitis, joint osteophytes, navicular apparatus changes, subchondral bone cyst-like lesions, laminar abnormalities, and flexor tendon mineralization. Navicular bone lesions were commonly identified, particularly in forelimbs, and frequently occurred in conjunction with abnormalities of the podotrochlear (navicular apparatus) region. These findings suggest that remodeling of the navicular bone and associated podotrochlear (navicular apparatus) structures may represent an important component of chronic distal limb disease and lameness in some affected giraffe. Laminar abnormalities consistent with chronic laminitis were common but were predominantly grade 1 on CT scoring, with grade 2 or 3 changes uncommon at both the digit and animal levels. Juvenile giraffe (<3 years) exhibited minimal CT-detectable orthopedic change, whereas lesions were more common and more extensive in older animals. Forelimbs more frequently exhibited navicular changes, and laminar abnormalities were more common in adult males than females. Distal phalanx fractures were identified in a subset of digits and occurred only in digits with pedal osteitis; fracture presence and severity were positively associated with greater pedal osteitis severity. Histopathology corroborated CT findings, demonstrating chronic laminar disruption, bone remodeling, and degenerative tendinopathy. Overall, these findings characterize historical patterns of distal limb pathology within a necropsy-based cohort of giraffe under managed care and provide context for continued refinement of preventive hoof-care strategies, husbandry practices, and early diagnostic monitoring aimed at promoting long-term orthopedic health.
Citation: Dadone L, Foxworth S, Johnston MS, Han S, Bapodra-Villaverde P, Crook E, et al. (2026) Postmortem computed tomography and histopathology of distal limb lesions in giraffe (Giraffa spp.) under managed care. PLoS One 21(6): e0352507. https://doi.org/10.1371/journal.pone.0352507
Editor: Catalina I. Villamil, University of Puerto Rico Medical Sciences Campus: Universidad de Puerto Rico Recinto de Ciencias Medicas, UNITED STATES OF AMERICA
Received: February 14, 2026; Accepted: June 11, 2026; Published: June 26, 2026
Copyright: © 2026 Dadone et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: No external grant funding was received for the research conducted in this study. Participating institutions provided in-kind support, including staff time for necropsy, specimen collection, and imaging. Publication costs were supported by the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin–Madison. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Hoof overgrowth and chronic lameness are recognized clinical challenges reported in giraffe (Giraffa spp.) in managed care [1–4]. Diagnosis and treatment of foot-related conditions have traditionally required general anesthesia, which carries procedural risk and may limit the feasibility of frequent diagnostic assessment in some settings [5,6]. Although anesthesia safety has improved substantially with updated drug protocols and experienced teams [7–9], rare fatal complications have been reported, including during foot-related procedures [8,10]. Safer alternatives, such as standing sedation [6,11] and positive reinforcement training for foot presentation [12,13], have improved the ability to perform regular hoof care while reducing procedural risk.
A wide range of musculoskeletal and podiatric conditions have been associated with lameness in giraffe under managed care. Hoof disorders include overgrowth [1,2,12], laminitis [14], pododermatitis [15], and retained sole foreign bodies. Joint abnormalities include Mycoplasma-associated polyarthritis [16], osteoarthritis [3,17], osteochondritis dissecans [18], osteochondrosis [19], pigmented villonodular synovitis [20], and septic or ulcerative arthritis [21]. Osseous lesions of the distal limb include subchondral bone cysts [22], distal phalanx and metatarsal fractures [23–26], pedal osteitis [3], and phalangeal rotation [3]. Additional soft-tissue conditions include interdigital dermatitis, ligamentous injuries, tenosynovitis [21], neurologic dysfunction, and traumatic injuries [27,28].
Radiographic studies indicate that distal limb disease often begins early in giraffe under managed care. In one well-studied trained herd prior to routine corrective hoof trims, pedal osteitis occurred as early as one year of age, distal interphalangeal osteoarthritis was present in all individuals by seven years, and distal phalangeal fractures developed by ten years [3,12]. These early structural abnormalities may contribute to progressive, degenerative distal limb disease in older giraffe, particularly when hoof overgrowth and hoof capsule asymmetry persist for many years. Historically, many managed-care environments used extensive hard-surface indoor flooring and had limited access to standardized preventive hoof work, early-life behavioral training, and non-slip, shock-absorbing substrates. Updated practices, including rubberized flooring, dirt- or mulch-based substrates, early-life hoof training, safer standing sedation, and regular preventive trims, have been implemented within the past decade and were not available to most older animals in this study.
By contrast, free-ranging giraffe primarily exhibit lameness from traumatic causes, particularly snare injuries [29]. A radiographic survey of wild Nubian giraffe in Uganda found relatively consistent hoof shape and relatively uncommon evidence of distal limb pathology [30], and baseline gross and histologic evaluation of free-ranging southern giraffe feet demonstrated intact corium and digital cushion architecture without evidence of laminitis, pedal osteitis, or navicular pathology [31]. Collectively, these findings support the hypothesis that many chronic degenerative distal limb lesions identified in managed giraffe may relate to cumulative biomechanical, environmental, and husbandry-associated influences rather than to an inherent species-wide susceptibility. However, direct comparison between free-ranging and managed giraffe populations should be interpreted cautiously because study populations, methodologies, and environmental conditions differ substantially. Substrate, enclosure design, exercise opportunities, and hoof-care schedules allow managed care facilities to improve environments and well-being. Importantly, many giraffe included in this historical cohort lived substantial portions of their lives prior to the widespread adoption of contemporary preventive hoof-care programs, structured behavioral hoof training, softer variable substrates, and browse-focused nutritional strategies now increasingly incorporated into managed giraffe care.
Radiographic evaluation of distal limb pathology carries inherent limitations due to superimposition of osseous structures and limited differentiation of soft tissues. Ultrasonography may provide additional soft tissue assessment; however, in large zoo ungulates its use is often constrained by the need for specialized behavioral training of the animal to permit safe positioning and limb access—or alternatively, chemical restraint or general anesthesia—as well as by the operator-dependent nature of the modality. Cross-sectional imaging modalities such as computed tomography (CT) reduce superimposition of osseous structures and improve visualization of many osseous and selected soft-tissue abnormalities relative to conventional radiography. Although antemortem CT of adult giraffe limbs is currently impractical in most clinical settings, postmortem CT provides an opportunity to characterize musculoskeletal pathology in three dimensions and to correlate imaging findings with gross and histopathologic changes.
The objective of this retrospective study was to characterize distal limb lesions identified on postmortem computed tomography (CT) in a necropsy-based cohort of giraffe under managed care, with targeted histopathology used to further define selected osseous and soft-tissue abnormalities. Characterizing lesion patterns within this historical cohort may provide context for future investigation of contemporary husbandry and preventive hoof-care strategies aimed at supporting long-term orthopedic health in giraffe under managed care.
Materials and methods
Animals
Twenty-one giraffe from 12 North American zoos were included in this retrospective study (Table 1). This study utilized a retrospective necropsy-based convenience sample enriched for giraffe with documented histories of lameness, hoof overgrowth, and/or suspected distal limb disease, particularly within the adult and geriatric age groups; therefore, findings are not intended to represent prevalence estimates for contemporary managed giraffe populations. Seventeen individuals were reticulated-hybrid giraffe and four were Masai giraffe. The cohort consisted of nine intact males and 12 females. Three animals were juveniles (<3 years old; range 18 days to 2.6 years), and the remaining 18 were adults or geriatric (range 11.0–32.9 years). Intermediate-aged subadults of 3–10 years of age were not represented in this necropsy cohort. Adult males had a median age of 20.0 years (range 11.7–29.0), and adult females had a median age of 23.8 years (range 11.0–32.9). Historical body weight, body condition, dietary composition, substrate exposure, enclosure design, and hoof-care records were inconsistently available among institutions and therefore were not incorporated into statistical analyses. For analysis, giraffe were assigned to three predefined age categories: < 3 years (juveniles), 11–19 years, and ≥20 years.
Six giraffe originated from one institution, three from a second, two each from another two zoos, and one from each of eight additional zoos were included. All animals died or were euthanized between 2004 and 2023. Distal limbs were removed at necropsy and stored frozen until CT imaging.
A total of 73 limbs were available for CT imaging: 40 forelimbs and 33 hindlimbs. Four distal limbs were available from 14 giraffe (66.7%); three from four giraffe (19.0%); both forelimbs only from two giraffe (9.5%); and a single forelimb from one giraffe (4.8%).
Ethics statement
Distal limb specimens evaluated in this study were obtained following natural death or euthanasia conducted for individual animal health and welfare reasons at participating institutions. No animals were euthanized specifically for this study, and no live-animal experimental procedures were performed. Postmortem CT imaging and targeted histopathologic evaluation were conducted specifically for this research project using limbs retained by participating institutions following necropsy. Participating institutions reviewed and approved imaging participation and specimen use according to their respective institutional processes where applicable. Formal Institutional Animal Care and Use Committee (IACUC) approval was not required because all study procedures were performed postmortem.
Computed Tomography (CT)
All available distal limbs were imaged postmortem using clinical helical multi-slice CT scanners at multiple institutions. Limbs were imaged while frozen and were not thawed prior to CT acquisition. Frozen postmortem imaging may alter soft-tissue attenuation and could contribute to artifactual mineralization appearance in some structures. Transverse images were acquired at slice thicknesses ranging from 1–2 mm. Acquisition parameters, including exposure settings and field of view, varied somewhat among institutions because of the retrospective multi-institutional design. Bone and soft tissues reconstruction algorithms were available for evaluation. The images were evaluated by an American College of Veterinary Radiology boarded radiologist (S.W.Y.), who was blinded to the clinical history of each patient, using the DICOM viewer OsiriX MD. Multiplanar reconstructions were performed to optimize the evaluation of structures in multiple planes. Although CT allowed detailed assessment of osseous remodeling and mineralized soft-tissue lesions, its sensitivity for subtle nonmineralized soft-tissue abnormalities is lower than that of magnetic resonance imaging (MRI). Anatomical location of some of the major ligament and tendon structures assessed on CT are illustrated in Figs 1 and 2.
Sagittal (A) and transverse (B) CT images of the distal forelimb illustrate major soft-tissue structures, including the suspensory ligament, superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), common digital extensor tendon, and collateral ligaments. Dorsal (D), palmar (P), medial (M), and lateral (L) orientations are indicated where applicable. In panel B, color overlays denote the following structures: suspensory ligament (orange), superficial digital flexor tendon (purple), deep digital flexor tendon (red), common digital extensor tendon (yellow), and medial and lateral collateral ligaments of the fetlock (blue). Gross dissections (C, D) demonstrate corresponding soft-tissue anatomy, highlighting the suspensory ligament (arrow), the SDFT/DDFT tendon bundle (star), and the extensor tendon bifurcation (arrowhead). Together, these images provide anatomical context for interpreting CT-detected lesions in the distal limb.
A labeled medial anatomical rendering depicts the proximal-to-distal course and relationships of major tendons and ligaments of the distal limb. Dorsal (D) and palmar (P) orientations are indicated. Structures are color-coded as indicated in the inset key. The image represents the medial aspect of the right distal limb. The image emphasizes the close spatial relationships among these structures and their role in digital stabilization during weight-bearing. This orientation aids correlation of CT and histopathology findings with functional anatomy.
Clinical Conditions Evaluated
Each digit was independently evaluated for osseous and soft-tissue abnormalities. Diagnoses were recorded at both the giraffe level (presence in ≥1 digit) and digit level. For animal-level laminitis severity summaries, the maximum laminitis score (0–3) observed in any scored digit for that individual (“maximum score per giraffe”) was used [3]. This approach provides an individual-level estimate of the most severe laminar change detected on CT while accommodating variability in limb availability among animals.
Osseous lesions evaluated included navicular bone disease, pedal osteitis, and distal phalanx (P3) fractures. Laminar pathology consistent with laminitis was evaluated separately. The fetlock, proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints were assessed for osteophytes and subchondral bone cyst-like lesions (SBCs). CT criteria for laminar pathology (laminitis), navicular disease, pedal osteitis, and subchondral bone cyst-like lesions were adapted from previously described definitions in domestic horses and nondomestic ungulates [3,32–34], with modifications intended to account for giraffe distal limb anatomy and CT appearance. Because validated giraffe-specific lesion nomenclature and CT grading systems remain incompletely established, selected terminology and lesion definitions were adapted from equine and nondomestic ungulate literature to facilitate comparative interpretation of distal limb pathology.
Soft-tissue structures assessed included collateral ligaments of the fetlock, PIP, and DIP joints; cruciate, oblique, interdigital, suspensory, and palmar digital annular ligaments; sesamoidean ligaments (intersesamoidean, oblique, and proximal sesamoidean); and the superficial (SDFT) and deep digital flexor tendons (DDFT). Relevant anatomical regions are shown in Figs 1 and 2. Selected lesions were subjectively scored from 0 (normal) to 3 (severe). P3 fractures were localized by foot and digit and assigned ordinal CT severity grades from 0 (absent) to 3 (severe).
CT findings categorized as navicular disease included one or more abnormalities of the distal sesamoid (navicular) bone, including sclerosis, widened synovial invaginations, subchondral bone cyst-like lesions, flexor cortical erosions, or loss of normal trabecular architecture, consistent with previously described imaging criteria [35–38].
Histopathology
Representative tissues were selectively, rather than systematically, collected from digits exhibiting a spectrum of CT abnormalities (mild to severe) or lesions considered clinically or anatomically relevant. Tissues were fixed in 10% neutral-buffered formalin, routinely processed, sectioned at 5 μm, and stained with hematoxylin and eosin (H&E). Samples originated from the feet of six giraffe. All slides were evaluated by a board-certified veterinary pathologist to corroborate CT interpretations and to further characterize laminar, osseous, tendon, and ligament pathology (Figs 3–5). Histologic sampling was intentionally targeted rather than comprehensive and was designed primarily to corroborate CT-detected lesions and assess lesion chronicity rather than to independently estimate lesion prevalence or severity distributions.
A) Transverse CT image at the level of the distal phalanx from a histologically unremarkable forelimb demonstrates organized laminar architecture. Dorsal (D) and palmar (P) orientations are indicated. B) A giraffe with chronic laminitis shows irregular dorsal laminar margins along the dorsal hoof wall and perilaminar soft tissue irregularity (open arrowheads) on CT, consistent with chronic laminar disruption. C) Histologic section of histologically unremarkable lamina shows thin, regularly spaced epidermal and dermal lamellae. D) Chronic laminitis is characterized histologically by widened, blunted, and disorganized laminae with expansion of interlaminar spaces (H&E, 100×). Together, these paired CT and histologic images illustrate CT–histology concordance for chronic laminar injury.
A) Sagittal CT image of the distal phalanx reveals irregular osteolysis, cortical thinning, and multifocal hypoattenuating defects along the solar/palmar aspect of the distal phalanx (arrowhead), consistent with moderate-to-severe pedal osteitis. Concurrently, there is a distal phalanx (P3) fracture (arrow). Dorsal (D) and palmar (P) orientations are indicated. B) Gross appearance of a relatively unaffected distal phalanx solar surface with smooth cortical margins and minimal surface porosity. C) Affected distal phalanx solar surface demonstrates marked porosity, cortical loss, and exposure of underlying trabecular bone (arrowhead), compatible with severe pedal osteitis. D) Histologically unremarkable distal phalanx histology shows dense, well-organized trabecular bone. E) Affected distal phalanx exhibits disorganized, vacuolated trabeculae with reduced structural integrity, supporting CT evidence of chronic pedal osteitis (H&E, 100×). These findings illustrate strong CT–pathology concordance for diagnosing chronic osseous degeneration.
A) Transverse CT image through the distal digit identifies mineralization within the suspensory ligament (arrowhead). Dorsal (D) and palmar (P) orientations are indicated. B) Mineralization is also present within the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT) of the palmar soft tissues; asymmetric DDFT size may reflect chronic remodeling and possible superimposed acute injury. C) Histologic section of a flexor tendon shows severe fibrosis with cartilaginous and osseous metaplasia (arrowhead), consistent with chronic degenerative tendinopathy (H&E, 100×). These CT and microscopic findings demonstrate the multifocal nature of tendon and ligament degeneration in adult giraffe and support attention to early monitoring and hoof balance.
Statistical Methods
Descriptive statistics were calculated for each lesion and expressed as percentages at both the giraffe and digit levels. For binary presence/absence analysis, CT scores of 1–3 were categorized as “present.” Differences between independent groups (e.g., sex) were evaluated using Fisher’s exact test, and paired comparisons (fore vs. hind limbs; medial vs. lateral digits) using McNemar’s test. Ordinal severity scores were compared between groups using Mann–Whitney U tests, and associations between ordinal grades were assessed using Spearman rank correlation. Statistical significance was defined as p < 0.05.
Because digits are clustered within feet and within individuals, observations are not statistically independent. Therefore, digit-level inferential analyses should be interpreted as exploratory and are intended primarily to identify lesion co-occurrence patterns rather than to support causal inference or individual-level risk prediction. Given the small sample size and uneven limb availability per animal, more complex clustered or mixed-effects models were not applied and are beyond the scope of this descriptive study. Clustered statistical approaches (e.g., generalized estimating equations or mixed-effect models) were considered; however, the limited number of individual giraffe and uneven limb availability among animals reduced model stability and increased risk of overfitting. No adjustments were made for multiple comparisons; p-values are provided to highlight potential patterns rather than to imply definitive thresholds of clinical significance. Accordingly, statistical findings should be interpreted as supportive of lesion-pattern characterization within this cohort rather than definitive evidence of population-level associations.
For a small number of digit–lesion combinations, scores were missing due to incomplete scoring as a result of incomplete inclusion of structures in the provided anatomy; denominators are reported where applicable.
Results
Within this necropsy-based historical cohort of giraffe under managed care, CT-detectable distal limb pathology showed marked age-associated patterns. Juvenile giraffe (<3 yr) exhibited minimal CT-detectable osseous abnormalities, whereas all giraffe ≥11 yr exhibited CT-detectable osseous pathology, and many also demonstrated laminar and soft-tissue changes (Tables 2–4). In adults, pedal osteitis, joint osteophytes, subchondral bone cyst-like lesions (SBCs), navicular disease characterized on CT by flexor cortical irregularity, sclerosis, and cystic remodeling of the distal sesamoid bone, and distal phalanx (P3) fractures were commonly identified and frequently graded as moderate to severe (Tables 2, 3, 5). Laminar abnormalities consistent with chronic laminitis were also frequently identified but were most commonly graded as mild (Tables 2, 3, 5). Soft-tissue abnormalities, including deep digital flexor tendon (DDFT) and superficial digital flexor tendon (SDFT) mineralization, collateral ligament desmopathy, and distal sesamoidean ligament pathology, were similarly common (Tables 3, 4, 6). Representative CT and gross anatomical images illustrating tendon and ligament orientation in the distal limb are shown in Figs 1 and 2. Several major lesions, particularly navicular disease (and to a lesser degree PIP osteophytes), showed a forelimb predilection. No consistent medial–lateral digit differences were detected. At the animal level, laminitis was the only major lesion with a significant sex association; additional sex-related differences in intersesamoidean ligament pathology were identified at the digit level (see below; Tables 3, 4, 6, 7). The raw CT scoring data used to generate the descriptive summaries and exploratory statistical analyses are provided in S1 Dataset.
Animal-level findings
Available historical medical records indicated that most adult and geriatric giraffe had documented histories of lameness, hoof overgrowth, or both, whereas juvenile giraffe rarely exhibited hoof-related concerns. Postmortem CT examination identified hoof overgrowth in most adult or senior giraffe but not in juveniles; in a subset of cases, feet had been trimmed after death.
Juveniles (<3 yr) had minimal osseous pathology. Pedal osteitis, DIP osteophytes, and P3 fractures were not observed (0/3), and only isolated mild abnormalities were detected (navicular disease 1/3; laminitis 1/3) (Table 3). Juvenile sample size was small (n = 3), so these findings should be interpreted cautiously, but align with previous clinical and imaging observations that substantial degenerative distal limb disease is uncommon in young giraffe.
Distal limb pathology was widespread in adults (≥11 yr). Pedal osteitis and DIP osteophytes were present in all adults, while navicular disease, laminar pathology, and P3 fractures were common and more frequent in older age groups (Table 3).
CT abnormalities consistent with laminitis were present in approximately two-thirds of giraffe; when present, maximum severity at the animal level was most often mild, with moderate-to-severe laminitis observed in a minority of individuals (Table 5).
Soft-tissue pathology.
Collateral ligament abnormalities were absent in juveniles but common in adults (e.g., DIP collateral desmopathy: 7/7 in 11–19 yr; 10/11 in ≥20 yr) (Table 3).
CT abnormalities involving flexor tendons were frequently identified in adults. DDFT mineralization occurred in 6/7 giraffe aged 11–19 yr and 6/11 ≥ 20 yr. SDFT mineralization occurred in 4/7 and 8/11, respectively. Cruciate ligament mineralization occurred in 5/7 and 7/11 giraffe; oblique ligament mineralization in 3/7 and 8/11. Age-associated patterns for tendon and ligament lesions are summarized at the animal and digit levels in Tables 3 and 4.
Sex differences.
Because all juveniles were female, sex comparisons were restricted to adults (n = 18). Most major osseous lesions were similarly prevalent between sexes. Laminitis was the only major lesion with a significant sex difference: it occurred in all adult males (9/9) compared with 4/9 adult females (44.4%) (p = 0.029) (Table 3). Adult males in managed care are generally larger-bodied than females; however, body weight data were not consistently available for formal statistical analysis in this cohort.
Fore vs. Hind limbs.
Among 18 giraffe with both forelimbs and hind limbs available, navicular disease was identified more frequently in forelimbs (14/18; 78%) than hindlimbs (7/18; 39%) (p = 0.016). PIP osteophytes and oblique ligament mineralization showed similar but non-significant forelimb trends. P3 fractures were more common in the forelimbs (6/18 vs. 3/18), although this difference was not statistically significant (Tables 2–4).
Medial vs. lateral digits.
No consistent statistically significant medial–lateral digit predilection for major lesions at an animal level was identified. Navicular disease occurred in at least one medial digit in 15/21 giraffe and in at least one lateral digit in 16/21 giraffe (p = 1.0), with similar symmetry observed across other lesions (Tables 2, 4, 6, 7).
Digit-level findings
Overall prevalence.
At the digit level, pedal osteitis and DIP osteophytes were the most frequently identified osseous abnormalities, followed by navicular disease, PIP osteophytes, DIP SBCs, and laminar pathology; flexor tendon mineralization and ligament lesions were also common (Table 2).
Digit-level age differences.
Juvenile digits (<3 yr) rarely exhibited degenerative change (e.g., pedal osteitis 0/24; DIP osteophytes 0/24). In contrast, pedal osteitis and DIP osteophytes were present in nearly all adult digits, while PIP subchondral bone cyst-like lesions were significantly more common in giraffe ≥20 years of age (Table 2). All adults had pedal osteitis, DIP osteophytes, and PIP osteophytes in at least one digit, and approximately half had at least one P3 fracture (Tables 2, 3).
Digit-level soft-tissue patterns.
DDFT mineralization was identified in 12/24 (50.0%) juvenile digits and in adults (18/46 [39%] in 11–19 yr; 25/74 [34%] in ≥20 yr). SDFT mineralization was not detected in juvenile digits (0/24) but was present in 10/44 (23%) digits in 11–19 yr giraffe and 28/74 (37.8%) digits in ≥20 yr giraffe. These tendon abnormalities frequently co-occurred with collateral ligament and sesamoidean ligament abnormalities, consistent with multifocal soft-tissue degeneration (Tables 4 and 6; Figs 1 and 2).
Digit-level sex and limb differences.
Sex comparisons at the digit level were restricted to adults. Laminitis was more common in male than female digits (42/60 [70%] vs. 20/60 [33%] of digits scored for laminitis; p < 0.001). Intersesamoidean ligament pathology was more common in females (44/58 [76%] vs. 10/60 [17%] of digits scored for this lesion; p < 0.001). Navicular disease and PIP osteophytes were significantly more common in forelimb digits. No tendon lesions showed a sex-based pattern, and no consistent medial–lateral differences were identified (Tables 2, 4, 6, 7). Digit-level tendon comparisons should be interpreted cautiously due to digit clustering and missing scoring in some digits; at the animal level, DDFT and SDFT mineralization prevalence did not differ by sex.
Lesion severity.
Moderate-to-severe (score ≥2) lesions were identified across multiple osseous and soft-tissue categories. Pedal osteitis was moderate-to-severe in 48/146 scored digits (33%), DIP osteophytes in 45/144 (31% of digits scored for this lesion), and navicular disease in 41/146 scored digits (28%). Moderate-to-severe DDFT and SDFT mineralization occurred in 14/144 (10%) and 18/142 (13%) scored digits, respectively. At the animal level, severe (score 3) DIP osteophytes occurred in 8/21 giraffe (38.1%), and severe navicular disease occurred in 5/21 giraffe (23.8%) (Tables 5 and 6).
Laminitis was predominantly mild, with 57/146 digits (39%) demonstrating mild laminitis (score 1), whereas moderate (score 2) and severe (score 3) laminitis were uncommon (4/146 [2.7%] and 3/146 [2.1%], respectively). Overall, only 7/146 digits (4.8%) had laminitis scores ≥2.
Laminitis co-occurrence patterns
Digits with CT abnormalities consistent with laminitis were significantly more likely to have pedal osteitis (61/64 [95%] vs. 54/80 [68%] in digits without laminitis; p < 0.001) and DIP osteophytes (58/64 [91%] vs. 49/80 [61%]; p < 0.001). Moderate-to-severe laminitis (score ≥2) was uncommon but more likely to co-occur with moderate-to-severe pedal osteitis (6/7 [86%] vs. 42/137 [31%] of digits with laminitis scores <2; p = 0.005).
Association between Pedal Osteitis and P3 Fractures.
Pedal osteitis and P3 fractures were closely linked at both the digit and foot level. At the digit level (n = 146 digits), P3 fractures were identified in 25/146 (17.1%) digits and occurred exclusively in digits with pedal osteitis. Digits with P3 fractures were significantly more likely to have pedal osteitis than digits without fractures (25/25 [100%] vs. 92/121 [76.0%]; Fisher’s exact test, p = 0.004). Pedal osteitis severity was also greater in digits with P3 fractures (median grade 2, range 1–3) than in digits without fractures (median grade 1, range 0–3; Mann–Whitney U test, p < 0.001), and pedal osteitis grade showed a moderate positive association with P3 fracture grade (Spearman’s ρ = 0.34, p < 0.001; Table 7). These findings support a positive association between increasing pedal osteitis severity and severity of distal phalanx fractures within this cohort.
Distal phalanx fractures also showed strong associations with DIP SBCs and navicular disease. DIP SBCs were present in all fracture-positive digits (25/25 [100%]) compared with 44/121 (36.4%) fracture-negative digits (p < 0.001). Navicular disease co-occurred in most fracture-positive digits (23/25 [92%]) compared with 51/121 (42%) fracture-negative digits (p < 0.001). Fracture-positive digits also had significantly higher median scores for DIP SBCs, navicular disease, and PIP osteophytes compared with fracture-negative digits (all p ≤ 0.001; Table 7).
At the foot level (maximum score across both digits per foot; n = 73 feet), pedal osteitis was present in 59/73 (80.8%) feet and P3 fractures in 16/73 (21.9%) feet. P3 fractures occurred only in feet with pedal osteitis (16/59 [27.1%] vs. 0/14 [0%] in feet without pedal osteitis; Fisher’s exact test, p = 0.030). Maximum pedal osteitis and P3 fracture grades were positively associated at the foot level (Spearman’s ρ = 0.42, p < 0.001; Table 7).
Histopathology
Histopathologic evaluation generally corroborated CT findings and provided insight into lesion chronicity. In juvenile giraffe (<3 yr), laminar architecture, trabecular bone, and tendon structure were largely normal, with only minimal remodeling present.
In adult giraffe, CT evidence of laminar abnormalities consistent with chronic laminitis corresponded to chronic laminar disruption, including widening and blunting of epidermal and dermal laminae, expanded interlaminar spaces, and loss of normal parallel alignment (Fig 3).
CT findings consistent with pedal osteitis corresponded to disorganized and thinned bony trabeculae, with osteolytic remodeling, cortical porosity, and areas of active bone resorption along the solar and palmar margins of P3 (Fig 4). Digits with severe CT osteitis showed marked loss of trabecular integrity.
Tendon and ligament histopathology confirmed chronic degenerative changes. Affected DDFT and SDFT tendons exhibited fibrosis, fibrocartilaginous and osseous metaplasia, focal mineralization, and disrupted collagen fiber architecture (Fig 5). Distal sesamoidean and suspensory ligaments showed similar patterns of fibrosis and dystrophic mineralization. Overall, histopathologic findings supported CT characterization of chronic osseous and soft-tissue remodeling within affected digits.
Discussion
Distal limb disease as a progressive, multi-tissue process
This multi-institutional CT and histopathology study identified distal limb disease as a common finding within this historical necropsy cohort of giraffe in managed care and increased markedly with age (Tables 2–4). Juvenile giraffe (<3 years old) showed few detectable lesions, whereas all giraffe ≥11 years had CT-detectable osseous pathology, and many also exhibited laminar and soft-tissue changes. Osseous remodeling, including pedal osteitis, distal interphalangeal (DIP) and proximal interphalangeal (PIP) osteophytes, subchondral bone cyst-like lesions, navicular disease, and distal phalanx (P3) fractures, were widespread in adults, while laminar pathology and soft-tissue degeneration were also common (Tables 2–6). Soft-tissue abnormalities, such as deep and superficial digital flexor tendon mineralization, collateral ligament desmopathy, and distal sesamoidean ligament degeneration, were similarly prevalent (Tables 4 and 6; Figs 1, 2, 5). Together, these findings support the interpretation that distal limb disease in this cohort of giraffe may reflect a progressive, multi-tissue process in which mechanical, environmental, and potentially metabolic influences may have accumulated over years of managed care.
Navicular disease and the navicular apparatus
Navicular disease was common in this cohort and demonstrated a forelimb predilection, which may reflect differing biomechanical loading between the forelimbs and hindlimbs. In horses, pathology within the navicular apparatus (podotrochlear region), including the distal sesamoid bone, deep digital flexor tendon (DDFT), navicular bursa, and associated ligaments is a well-recognized contributor to chronic forelimb lameness and often reflects cumulative biomechanical stress rather than a single traumatic lesion type [35–38]. While direct clinical extrapolation from equine to giraffe species should be made cautiously, the high frequency of CT-detected navicular remodeling in conjunction with DDFT mineralization in giraffe suggests that disease of the navicular apparatus may represent an important contributor to chronic distal limb disease and lameness in some affected individuals. Given the reported correlation between heel conformation and navicular disease in equine species [39], the early identification of hoof overgrowth and hoof-capsule distortion, and trimming strategies that restore more physiologic breakover and caudal support could potentially reduce cumulative biomechanical stress within the navicular apparatus in managed giraffe. Additional efforts to optimize substrates and exercise opportunities to mimic their natural environment may also result in reduced biomechanical stress, and secondary osseous remodeling of the distal phalanx.
In one example foot with navicular apparatus disease (Fig 6), CT images demonstrated collapse and displacement of the digital cushion relative to the solar plane, compared with the normal digital cushion alignment described in free-ranging giraffe [31] and consistent with altered palmar soft-tissue configuration within the navicular apparatus. Digital cushion conformation was not systematically assessed in this cohort; however, the altered digital cushion orientation could potentially influence biomechanical loading within the navicular apparatus. However, this observation was descriptive and was not systematically evaluated within this cohort, warranting further prospective investigation.
Sagittal postmortem computed tomography (CT) image of the palmar aspect of the distal forelimb demonstrating navicular apparatus pathology. Dorsal (D) and palmar (P) orientations are indicated. The distal sesamoid (navicular) bone exhibits irregular flexor cortical erosions, widened synovial invaginations, and cystic change involving both the flexor surface and the central spongiosa region of the bone (arrowheads). There is loss of normal trabecular architecture with surrounding sclerosis, consistent with chronic osseous remodeling. These CT features are characteristic of navicular apparatus disease. In this limb, the digital cushion appears compressed and displaced toward the palmar aspect relative to the solar plane of the foot (star), compared with the normal digital cushion alignment described in free-ranging giraffe.
Hoof imbalance, collateral ligaments, and the flexor apparatus
A high prevalence of collateral ligament desmopathy and flexor apparatus degeneration (DDFT/SDFT mineralization and distal sesamoidean ligament pathology) supports a substantial soft-tissue component to chronic distal limb disease in this cohort. One potential contributor is chronic hoof capsule imbalance associated with long-standing overgrowth and altered wear patterns, which can modify mediolateral and dorsopalmar load distribution within the digit and increase strain on stabilizing ligaments and the flexor apparatus. In horses, experimental alteration of palmar angle changes strain within the distal interphalangeal joint collateral ligaments, and toe and heel elevation measurably alter calculated strain in the superficial and deep digital flexor tendons [40,41]. While this retrospective dataset did not identify a consistent medial–lateral digit predilection for major lesions, the frequency and co-occurrence of chronic collateral ligament and flexor apparatus abnormalities are consistent with chronic degenerative remodeling that may reflect cumulative abnormal biomechanical strain, metabolic influences, or a combination of factors. In the equine species, a correlation between chronic injury of the flexor apparatus with dorsopalmar/plantar imbalances has been suggested. In cloven hoof species, it would be reasonable to assume that altered shape of the hoof may contribute to altered biomechanical strain in not only a dorsal to palmar/plantar direction, but also in a medial to lateral orientation, supporting continued emphasis on early detection and management of hoof overgrowth and imbalance through structured preventive trimming, substrate optimization, and training-based routine foot evaluation.
Laminitis patterns in managed giraffe: mechanical, structural, and metabolic considerations
Laminar pathology consistent with chronic laminitis was common in this cohort but typically mild. At the digit level, most laminitis-positive digits were scored as mild, with only a small subset reaching moderate-to-severe scores (Tables 2 and 5). At the animal level, using a conservative maximum-severity-per-giraffe approach, laminitis was present in approximately two-thirds of individuals and was most often mild, with moderate-to-severe laminitis observed in a minority of giraffe (Table 3). This pattern suggests that CT-detectable laminar change may be frequent in older managed giraffe, though the clinical significance of mild CT-detected laminar abnormalities in giraffe remains incompletely defined and may overlap with other concurrent distal limb lesions.
Comparison with baseline hoof anatomy and histology in free-ranging giraffe provides important context for interpreting these findings. Detailed gross and histologic evaluation of the hoof capsule, corium, and digital cushion in wild southern giraffe demonstrated intact laminar and papillary architecture, absence of pedal osteitis or navicular pathology, and no histologic evidence of laminitis [31]. The absence of laminar pathology in naturally worn feet suggests that laminar abnormalities identified in this cohort may not represent inevitable age-related changes alone, and is more likely influenced by managed-care factors such as substrate, hoof overgrowth, altered biomechanics, and diet.
A nutritional or metabolic component may also have contributed to the high prevalence, but generally low severity of laminitis observed in this historical cohort. Historically, some managed-care diets for giraffe may have included higher proportions of starch-containing concentrates and less browse diversity compared with many contemporary feeding strategies. In domestic ruminants and horses, chronic low-grade ruminal acidosis and associated metabolic perturbations have been linked to laminar inflammation and microvascular dysfunction, frequently resulting in subclinical or mild laminar pathology rather than fulminant laminitis. Although direct dietary or metabolic data were not available for this retrospective cohort, the predominance of mild laminitis scores could potentially reflect chronic, low-grade metabolic influences acting in concert with mechanical stressors rather than acute severe laminar failure.
Notably, laminitis showed no direct association with distal phalanx fracture in this dataset, and fracture-positive digits were confined to those exhibiting pedal osteitis. This finding suggests that laminar change alone—particularly when low-grade—is insufficient to predict fracture risk without concurrent compromise of distal phalanx bone quality. Laminitis should therefore be interpreted within the broader lesion context, including osseous remodeling, joint degeneration, and overall foot biomechanics, rather than as an isolated indicator of catastrophic distal limb failure.
Comparison with prior work and age-associated patterns
The age-associated patterns identified here are consistent with earlier radiographic and clinical studies of giraffe under managed care, which reported that distal limb disease can begin early in life and become progressively more extensive with time. In a well-studied trained herd, pedal osteitis was detected as early as one year of age, distal interphalangeal osteoarthritis occurred in all individuals by seven years, and distal phalanx fractures first appeared at ten years, prior to the implementation of routine corrective hoof trims in that population [3,12]. These early structural abnormalities, when uncorrected, may contribute to the multifocal and chronic pathology observed in older adults (Figs 3–6; Tables 2–5). Although juvenile numbers in the present study were limited and subadults (3–10 years) were not represented, the near-absence of major osseous lesions in juveniles is consistent with prior observations and supports the concept that most degenerative lesions accumulate over years of managed care. Notably, mild deep digital flexor tendon (DDFT) mineralization was identified in a subset of juvenile digits. Because severe degenerative soft-tissue change was otherwise absent in this age group, this finding may reflect physiologic mineralization, postmortem imaging artifact associated with frozen-limb CT evaluation, or early remodeling of uncertain clinical significance. Further prospective evaluation of soft-tissue changes in young giraffe is warranted.
Relationship between pedal osteitis, joint degeneration, subchondral lesions, and P3 fractures
The current CT-based analysis further clarifies associations between distal phalanx remodeling and P3 fractures. At both the digit and foot levels, increasing severity of pedal osteitis was significantly associated with both the presence and severity of P3 fractures, with fractures occurring only in digits and feet exhibiting pedal osteitis (Table 7). These findings support a possible continuum in which progressive cortical and trabecular remodeling of the distal phalanx may reduce structural tolerance to mechanical loading, predisposing to fracture as bone quality deteriorates. These findings are consistent with prior radiographic work reporting an association between pedal osteitis severity and fracture risk in giraffe [3].
Fracture-positive digits also clustered within a broader degenerative joint–subchondral–bone quality lesion complex. P3 fractures showed strong co-occurrence with DIP subchondral bone cyst-like lesions, navicular disease, and osteoarthritic changes (Table 7). Chronic joint degeneration and subchondral bone remodeling likely alter load distribution across the distal phalanx, increasing focal stress and lowering the threshold for fracture when bone quality is compromised. Alternatively, the presence of a fracture, especially if articular involvement is identified, may contribute to progressive degenerative joint diseases, due to physical disruption to the synovium and joint space, as well as altered weight bearing. While causality cannot be inferred from this retrospective dataset, the consistency of these co-occurrence patterns supports early detection and management of chronic pedal osteitis and degenerative DIP/navicular changes as a fracture risk-reduction strategy in managed giraffe.
Limb loading patterns, sex differences, and laminitis
A forelimb predilection was identified for navicular disease and, to a lesser degree, PIP osteophytes. These findings may reflect differing biomechanical loading patterns between the forelimbs and hindlimbs in giraffe. Chronic mechanical loading and long-standing hoof imbalance may predispose the navicular apparatus, flexor tendons, and associated ligaments to cumulative strain and degenerative remodeling; in this context, distal phalanx bone quality, as reflected by pedal osteitis severity, appears to be a critical component of fracture risk.
Laminitis was significantly more frequent in adult males than females at both the animal and digit levels (Tables 2 and 3). Adult males may be managed individually overnight for safety and husbandry reasons, including reducing the risk of injury associated with aggressive interactions, which could potentially increase repetitive locomotor behaviors, prolonged standing, or altered loading patterns. Differences in substrate, enclosure geometry, resting behavior, and nutritional management may therefore contribute to chronic laminar strain. Greater body mass and associated limb loading in adult males may also contribute to these observed sex-associated differences. Historically, males may also have received higher caloric rations, and when combined with limited browse availability and higher dietary starch content, this may have contributed to increased susceptibility to chronic low-grade laminar abnormalities. Many institutions have since transitioned toward browse-rich, high-fiber diets alongside improvements in substrate and proactive hoof care, which are expected to reduce both mechanical and metabolic contributors to laminar pathology in contemporary giraffe populations.
Husbandry and medical context
The husbandry context in which adult giraffe in this study lived is important for interpreting the severity and distribution of lesions. For many years, giraffe in North American zoos were commonly housed on hard-surface indoor flooring, which may increase mechanical loading and contribute to osteitis, sole bruising, and hoof capsule distortion. Preventive hoof trimming, early-life behavioral hoof training, and routine voluntary foot presentations were not yet widely adopted. Over the past decade, husbandry practices have evolved substantially, incorporating rubberized flooring, natural substrates, browse-rich diets, structured preventive trimming programs, and positive reinforcement training beginning early in life. These advances were not available to most individuals in this historical necropsy cohort and may have contributed to lesion prevalence, chronicity, and severity. Accordingly, lesion severity and chronicity observed in this historical cohort may not reflect orthopedic outcomes achievable under many contemporary managed-care conditions.
Advances in giraffe medical care have also improved the feasibility and safety of foot evaluations. Refinement of standing sedation protocols, along with the use of giraffe restraint devices and purpose-built chutes, has enabled earlier diagnostic assessment and more frequent preventive intervention while reducing reliance on general anesthesia. Because these tools were implemented only recently, they were not widely available during the early lives of many giraffe in this cohort.
Role of CT and histopathology
CT provided detailed three-dimensional visualization of lesions that can be difficult to assess using radiography alone due to superimposition, including navicular remodeling, subchondral bone cyst-like lesions, and soft-tissue mineralization and enthesopathy. Histopathology generally corroborated CT findings and supported lesion chronicity, including laminar disruption, trabecular remodeling consistent with pedal osteitis, and degenerative tendinopathy and desmopathy. Together, CT and targeted histopathology allowed characterization of historical lesion patterns and associated tissue changes within this cohort, while more accessible modalities, such as standardized hoof photography, serial radiographs, thermography, and targeted ultrasonography, can be integrated into ongoing clinical management of live animals.
Limitations of CT soft tissue contrast and implications for future management
Because this study evaluated a necropsy-based convenience sample enriched for clinically affected individuals across a long historical window (2004–2023), these findings are best interpreted as lesion characterization within a high-risk cohort and should not be extrapolated to overall prevalence or welfare outcomes in contemporary managed giraffe programs. Clinically normal age-matched managed-care giraffe were not available for comparison, limiting the ability to distinguish some chronic lesions from potential age-related adaptive remodeling changes. Limb availability varied among animals, and limbs were imaged frozen following variable sites of amputation, which in some cases limited evaluation of more proximal structures. Frozen postmortem imaging may also alter soft-tissue attenuation and mineralization appearance in some structures.
Additionally, digits within individuals are not statistically independent; therefore, digit-level analyses should be interpreted as exploratory indicators of co-occurrence rather than individual-level risk predictors. The retrospective design precludes conclusions about lesion progression over time or the clinical significance of mild lesions in all cases. Accordingly, lesion frequencies reported here are best interpreted as describing a historical high-risk subset rather than as prevalence estimates for contemporary managed giraffe populations.
Another limitation is in the inherently lower soft-tissue contrast resolution of CT compared with magnetic resonance imaging (MRI), which may reduce sensitivity for subtle nonmineralized tendon, ligament, or other soft-tissue abnormalities. MRI was not consistently available for comparison in this retrospective cohort because of logistical and financial limitations associated with imaging large giraffe limbs.
Because most animals in this cohort were clinically affected adults or geriatric giraffe originating from historical management periods, caution should be exercised when extrapolating lesion frequency or severity to younger or more contemporarily managed giraffe populations.
Despite these limitations, the consistency of findings across institutions aligns with prior radiographic, thermographic, and pathological descriptions of giraffe distal limb disease. Collectively, these findings support continued emphasis on early-life preventive monitoring, routine hoof assessment, and proactive hoof-care strategies alongside ongoing refinement of substrates, nutrition, and training-based foot presentation.
Prospective longitudinal evaluation of giraffe managed under contemporary husbandry conditions will be important for further characterizing the relationships among preventive hoof care, husbandry practices, pedal osteitis progression, laminar abnormalities, and fracture risk over time.
Conclusions
Distal limb disease was common in this historical necropsy cohort of giraffe in managed care and strongly associated with age, with all animals ≥11 years exhibiting CT-detectable osseous pathology, and many also exhibited laminar and soft-tissue changes, while juveniles had few or no lesions (Tables 2–4). Histopathology confirmed chronic laminar disruption, pedal osteitis, and degenerative tendon and ligament changes, supporting CT as a valuable postmortem tool for detailed evaluation of osseous and selected soft-tissue abnormalities in adult giraffe.
Although laminitis was frequently identified, it was predominantly mild at both the digit and animal levels. Comparison with baseline hoof anatomy and histology from free-ranging giraffe indicates that laminar pathology is not an inevitable age-related change but may reflect cumulative mechanical, environmental, and metabolic influences associated with historical managed-care conditions. Greater severity of pedal osteitis was associated with both the presence and severity of distal phalanx fractures, and fractures clustered with degenerative changes of the distal interphalangeal joint complex, underscoring the importance of distal phalanx bone quality in fracture susceptibility.
Most giraffe in this dataset lived many years before the widespread adoption of modern preventive hoof-care programs, softer substrates, browse-based nutrition, early-life behavioral training, and safer standing diagnostic techniques. These historical conditions likely contributed to the severity and chronicity of lesions observed and should be considered when interpreting the extent of pathology in this cohort. These findings highlight the importance of continued refinement of husbandry, nutrition, and preventive hoof-care strategies in managed giraffe populations. Early-life monitoring, routine hoof assessment, and proactive trimming, combined with improved flooring, diet, and feasible diagnostic surveillance, may contribute to reducing the severity and progression of distal limb disease and mitigate progressive pedal osteitis and fracture risk in future giraffe cohorts.
Supporting information
S1 Dataset. Raw computed tomography scoring data for distal limb lesions in managed-care giraffe (Giraffa spp.).
Spreadsheet containing de-identified giraffe, foot, and medial/lateral digit-level CT scoring data used to generate the descriptive summaries and exploratory statistical analyses reported in the manuscript. The file also includes definitions of column abbreviations and terminology.
https://doi.org/10.1371/journal.pone.0352507.s001
(XLSX)
Acknowledgments
The authors gratefully acknowledge Garden Valley Zoo, Out of Africa Wildlife Park, and Cheyenne Mountain Zoo for providing giraffe cases and access to postmortem materials that made this study possible. We also thank the collaborating zoos and veterinary hospitals for performing postmortem CT imaging and supporting data acquisition. The authors additionally acknowledge the zoo veterinarians, veterinary technicians, farriers, and animal care professionals who participated in Zoo Hoofstock Trim Program (ZHTP) courses and collaborative discussions that helped inform clinical perspectives on giraffe hoof health and preventive care.
The study was conceived while the corresponding author was employed at Cheyenne Mountain Zoo, and some cases included in this manuscript were managed during that period.
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