Medial and lateral of the knee can occur when the knee is in
The correct answer and explanation is:
Correct Answer:
Flexion
Explanation (Approximately 300 words):
Medial and lateral movements of the knee—specifically, medial (internal) and lateral (external) rotation—can occur when the knee is in flexion.
The knee joint is primarily a hinge joint, designed mainly for flexion (bending) and extension (straightening). However, it also allows a small degree of rotation, but this is only possible when the knee is not fully extended. When the knee is fully extended (locked in place), the ligaments are taut, especially the collateral and cruciate ligaments, which stabilize the joint and prevent rotation.
When the knee is in flexion, particularly around 20–30 degrees or more, these ligaments become relaxed enough to allow some rotational movement. This is when medial (internal) rotation and lateral (external) rotation of the tibia relative to the femur can occur. This rotation is essential for various activities such as walking, running, and changing directions.
For example:
- Medial rotation occurs when the foot is turned inward, causing the tibia to rotate toward the body’s midline.
- Lateral rotation occurs when the foot is turned outward, rotating the tibia away from the midline.
This rotation is also involved in the “screw-home mechanism” during the last portion of knee extension and the beginning of flexion. When the knee fully extends, the tibia rotates externally (laterally) to “lock” the joint. Conversely, when flexing the knee, the tibia rotates internally (medially) to “unlock” it.
In summary, medial and lateral rotation of the knee only occur when the knee is in flexion because the joint is unlocked and the surrounding structures are relaxed enough to permit this additional range of motion. This feature is vital for joint mobility, especially during dynamic and athletic movements.