Table 1.
List of the specimens.
Fig 1.
Trochlear groove angle measurements.
Magnetic resonance (MR) images of two cross-sections of the knee were used to measure the trochlear groove angle: between the medial condyle of the femur, intercondylar groove, and lateral condyle of the femur. (A) Plane consists of the vertical to the femoral axis, passing through three points: the medial trochlear peak (point #1), trochlear groove (point #2) and lateral trochlear peak (point #3). (B) Plane is parallel to the femoral axis, passing through passing through the peaks of medial (point #4) and lateral (point #5) femoral epicondyles. The patella facet angle on this plane was measured. CRL 52 mm sample image was shown as representing data.
Table 2.
List of landmarks for Procrustes analysis.
Fig 2.
Landmarks of the distal epicondyle coordinates for the distal epiphysis on vertical section for Procrustes analysis.
The landmarks of the magnetic resonance (MR) image were 15, including the lateral trochlear peak, medial epicondyle, and lateral epicondyle (No. 1, 5, and 14). Table 2 provides more details regarding these landmarks. CRL 52 mm sample image was shown as representing data.
Fig 3.
Development of distal femur bone and patella morphology during embryonic and fetal stages on the parallel plane of the femur axis.
The images show the femur and patella (blue). The surfaces of the underlying subchondral bone of the femoral condyle and trochlear groove were observed. All images were obtained from the knee joint of the right lower limb.
Fig 4.
Overview of knee joint development during embryonic and fetal stages.
The images show the femur, patella (blue), and tibia. Bone was reconstructed from all specimens, while the patella was reconstructed from Carnegie stage 22 specimens. All images were of the knee joint of the right lower limb, omitting the fibula.
Fig 5.
Trochlear groove measurements.
(A) 3D reconstructed images of Amira and magnetic resonance (MR) scans on parallel and vertical planes at five stages of crown-rump length (CRL). The upper two lanes show the vertical plane, while the lower two lanes show the parallel plane. (B) Trochlear groove angle A (red dots) decreased from approximately 160° to 130° during 21.2–100 mm crown-rump length (CRL) and remained constant at 185 mm CRL. In contrast, angle B (blue dots) remained constant at approximately 130° during 21.2–185 mm CRL. Based on the distribution of the data, polynomial fitting used for Angle A and linear fitting were used for Angle B. (C) Chronological changes in the trochlear groove. Angle A exhibited significantly larger values in the early than later CRL stages. Angle B showed no significant differences among the groups.
Table 3.
Results of the three-group comparison of landmark angles.
Fig 6.
Reconstructed Procrustes shape coordinates for the distal femoral epiphysis.
(A) Distal femoral shape was reconstructed from all specimens and adjusted to size for morphological comparison. (B) The reconstructed Procrustes image shows the formation of the trochlear groove (landmark #2) and sharpness of the peak of the lateral femoral condyle (landmark #1) with increasing crown-rump length (CRL). The numbers next to each dot indicate the landmark number.
Fig 7.
3D reconstructed models of the muscles involved in knee joint movement with leg skeleton during 37.2–170 mm crown-rump length (CRL).
Samples at 37.2, 43.5, 97, 128.1, and 170 mm CRL are shown. (A) Rectus femoris, (B) vastus, (C) semitendinosus, (D) semimembranosus, (E) long head of biceps femoris, and (F) short head of biceps femoris muscle.
Fig 8.
Chronological changes in the cross-section area (CSA) at the center of the thigh (A) and joint motions by each thigh muscles (B).
The CSA of all muscles increased gradually. The CSA of the vastus muscle increased dramatically from 100 mm crown-rump length (CRL). All joint motions increased slowly during 30–100 mm CRL, whereas rapidly after approximately 100 mm CRL. The vastus muscle activity increased dramatically. Based on the distribution of the data, exponential approximation was applied for each muscle’s joint motion data.
Table 4.
Correlation between patella angles A, B, and flexion and extension joint motion.