OCLC: 32442456
PROQUEST: 304114300
A dynamic model of the knee in the sagittal plane was developed and included in an optimal control model for maximum-height squat jumping and in a similar model for minimum-time kicking. The geometry of the femoral condyles and femoral groove was obtained from cadaver data. The tibial plateau was represented by a flat surface tilted 8° posteriorly from the long axis of the segment. The patella was defined as a small rectangular block with mass properties. Contact constraint forces between the femur and tibia and the femur and patella simulated reaction loads between these segments. A constant length for the patellar ligament simulated its high stiffness property. The knee model included four extensible ligaments spanning the tibio-femoral joint: anterior cruciate (ACL), posterior cruciate (PCL), lateral collateral, and medial collateral.
Static testing of the model indicated that the quadriceps increased the ACL load and decreased the PCL load; the hamstrings produced the opposite effect. Static cocontraction simulations indicated that the ACL could not be unloaded near full extension.
In the dynamic simulations for jumping, the peak compressive load at the tibio-femoral joint was approximately 8 times body weight with a peak load at the patello-femoral joint of nearly 6 times body weight. The PCL initially carried a load of about twice body weight, which decreased as the knee extended. The ACL reached a peak load of less than body weight near lull extension.
For kicking the peak compressive load at the tibio-femoral joint was approximately 6 times body weight with a peak load at the patello-femoral joint of about 7 times body weight. These forces occurred at the end of the kick as the knee approached the final flexed position. At this angle the ACL was slack while the PCL had a load of approximately twice body weight.
For both models, the muscles contributed from 34% to 100% of the tibio-femoral contact force. Except near full extension, the quadriceps contributed the majority of this force. The analyses of the kicking results show that the ACL may be unloaded even with quadriceps activation by execution of a properly coordinated dynamic activity.