Final answer:
Knee extension involves the quadriceps femoris acting as agonists, with the patella facilitating this movement over the femur. The femoral orientation and Q-angle, especially in women, affect knee mechanics and risk of injury. The knee is also supported by various ligaments that contribute to its stability.
Step-by-step explanation:
Knee extension is a common movement involving the quadriceps femoris, a group of four muscles located in the anterior compartment of the thigh. These muscles act as agonists during the extension motion. Conversely, when flexing the knee, the hamstrings serve as the antagonistic muscle group. The knee joint comprises the femoropatellar joint and the medial and lateral tibiofemoral joints, allowing for movement through a combination of rolling and gliding of the femur over the tibia.
The patella, also known as the kneecap, is a sesamoid bone within the quadriceps tendon that helps to protect it against friction from the femur. During the action of the quadriceps femoris, the patella slides vertically following a groove on the distal femur. This movement leads to knee extension, with the muscle also providing essential support and stability to the knee joint.
Factors like the Q-angle, which measures the lateral angle of the femur in relation to the vertical axis, especially in women due to their typically wider pelvis, can influence the mechanics and potential strain on the knee. Larger Q-angles may increase the risk of conditions like patellofemoral syndrome, underscoring the importance of the joint's structural integrity and support provided by various ligaments, including the collateral, posterior cruciate, and anterior cruciate ligaments.