We can't rotate our leg at the knee because the knee is a hinge joint, which is specifically designed for forward and backward movement.
Understanding the Knee Joint
The knee is a complex joint, but its primary function is to allow the leg to bend and straighten. This is largely dictated by the type of joint it is.
Hinge Joint Functionality
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A hinge joint allows movement in only one direction – like a door hinge.
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Reference: This is due to the presence of hinge joint in knee and elbow. Hinge joint allow movement in one direction only i.e., to and fro movement.04-Mar-2022
Why No Rotation?
- The structure of the bones (femur and tibia) and the ligaments surrounding the knee limit side-to-side or rotational movement.
- Ligaments are strong bands of tissue that connect bones and provide stability. In the knee, they are arranged in a way that primarily supports flexion (bending) and extension (straightening).
Comparison to Other Joints
To illustrate why the knee doesn't rotate, let's compare it to a joint that does:
| Joint | Type | Movement Allowed |
|---|---|---|
| Knee | Hinge | Primarily flexion (bending) and extension |
| Hip/Shoulder | Ball and Socket | Flexion, extension, abduction, adduction, rotation |
As you can see, ball and socket joints, like the hip, have a very different structure that permits a much wider range of motion including rotation. The knee's hinge joint simply isn't built for that.
