Tibial axis and patellar position relative to the femoral epicondylar axis during squatting☆
Section snippets
Materials and methods
Ten whole-leg, fresh-frozen human cadaver specimens were tested in a fixture designed to simulate squatting (Fig. 1) [4]. All specimens were examined grossly and radiographically and appeared normal. The quadriceps extensor mechanism, the biceps femoris, and the semimembranosus muscle bellies were dissected free approximately 10 cm proximal to their insertions and were sutured to loading straps. Intermedullary rods were cemented into the distal tibia and femoral neck and then secured to the
Results
The tibia rotated an average of 13° (SD, 3; range, 8°–17°) internally as the knee was moved from full extension (0°) to 90° (Fig. 3). Flexion of the knee from full extension to 15° produced, on average, 8° (SD, 3; range, 2°–11°) of internal rotation of the tibia, whereas movement from full extension to 30° of flexion, created 11° of internal rotation of the tibia (SD, 3; range, 5°–14°). On average, 60% and 81% of the internal rotation was produced by movement of the knee from full extension to
Discussion
The findings from this study are based on the “compound hinge model of knee kinematics” described previously [4]. A more suitable term might be the “two-axis theory” of tibiofemoral kinematics, because knee motion can be described by rotations about two axes carefully located and fixed in bone: the femoral epicondylar axis (flexion-extension) and the anatomic tibial axis (internal-external rotation). This is not to say that there are only 2 degrees of freedom in the tibiofemoral joint, but
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Benefits or funds were received in partial or total support of the research material described in this article from Stryker Howmedica Osteonics.