Final answer:
The patellofemoral compressive force is at its peak between 60 and 90 degrees of knee flexion, as supported by the engagement of the quadriceps muscle and the stability provided by knee ligaments such as the tibial and fibular collateral ligaments, and the anterior and posterior cruciate ligaments.
Step-by-step explanation:
During knee flexion, the patellofemoral compressive force is highest when the knee is flexed between 60 and 90 degrees. The force is due to the engagement of the quadriceps femoris muscle which increases as the knee flexes, thereby elevating the pressure between the patella and the femur. This force is critical for activities such as squatting and climbing stairs, where the knee needs to withstand increased loads.
The knee joint is supported by a number of ligaments including the tibial and fibular collateral ligaments, located on the sides of the knee, and the anterior and posterior cruciate ligaments which are found inside the joint capsule. These ligaments provide essential stability for the knee during movement, particularly during the transition between flexing and extending.