Table 1.
Baseline characteristics of patients.
Fig 1.
Measurements and comparison of patella-patellar tendon angle (PPTA) in patients who complained anterior knee pain.
In study group, measured PPTA on sagittal proton density-weighted images was (a) 138.2° in a 21-year-old man with medial patellar plica syndrome, (b) 138.0° in a 22-year-old man with chondromalacia patella, and (c) 137.8° in a 21-year-old man with infrapatellar fat pad syndrome. (d) However, in a 22-year-old man with no abnormality on MRI and diagnostic arthroscopy, the PPTA was 142.1° which was significantly higher than that of patients in study group.
Fig 2.
Knee MRI and arthroscopic findings of patients in study group.
(a, b) A 21-year-old man with medial patellar plica (MPP) syndrome showed thickened MPP (arrow) and impingement MPP (asterisk) between medial femoral condyle and patella. On MRI, the PPTA was 138.2°. (c, d) A 22-year-old man with chondromalacia patella showed contour defects in the cartilage surface of patella medial facet (arrow) and there was 1.5 ⅹ 1.5 cm sized cartilage defect (asterisk) in that area on arthroscopy. The PPTA was 138.0° in this patient. (e, f) A 21-year-old man with infrapatellar fat pad (IPFP) syndrome showed soft tissue infiltrations (arrows) at IPFP on MRI and fat tissue hypertrophy (asterisk) on arthroscopy. The PPTA was 137.8°.
Fig 3.
Comparison of PPTA between the two groups (study group vs. control group) and receiver operating characteristic (ROC) analysis to assess the performance of PPTA for the prediction of the risk of knee patellofemoral joint disorder.
(a) Box-plot showed mean PPTA was significantly lower in study group than control group (138.1 ± 4.2° vs. 142.1 ± 4.3°, p < 0.001). (b) The ROC curve of PPTA for predicting the patellofemoral joint disorder showed the AUC of 0.696 at a cutoff value of 138.3°, with a sensitivity of 70.3% and a specificity of 57.6%.
Table 2.
Comparison of baseline characteristics of patients in study group.