Knee lock refers to the problem that occurs when the knee cannot be straightened or bent. This locking most commonly happens when loose cartilage or a bone fragment has blocked or jammed the knee joint. A misalignment of the muscles or bones due to muscle strain or an injury also can cause this condition. In either situation, the knee can become stiff and frozen, which is accompanied by extreme pain. To treat knee lock, it is important to know what caused the initial symptoms.
Arthritis and natural aging can increase the risk for a knee lock. Over time, the cartilage that surrounds the bones in the knee can become worn out, causing it to begin to break off. The cartilage material can become lodged within the knee joint mechanism, making it impossible to bend the leg. If the cartilage is completely worn out, it is also possible for a chipped bone fragment to become jammed in the knee mechanism. This is referred to as an osteochondritis dissecans.
Intense exercise or a strain on the thigh muscles can cause a lock. Any weakness or tightness in the outer thigh muscles can affect the knee cap. The tightness causes a contraction of the muscle, which can result in a misalignment of the knee cap. It will remain stuck in this position until the muscle returns to normal. Even when the knee cap is aligned correctly, it can still take a considerable amount of time to gain the normal range of motion in the knee.
When a knee joint is injured or strained, there may be symptoms that are similar to a locked knee but it is not considered a true knee lock. A knee lock involves an inability to bend or move the knee, not just pain. A slight bump to the knee cap or running or jumping too hard can cause a knee lock sensation, which is called a pseudo- lock. Although the discomfort and pain can be real, the knee can still have a range of movement. The pseudo-lock typically goes away in a matter of days.
Anytime there is a restriction of movement in the knee, a medical evaluation should be done. If left unchecked, a bone fragment or loose cartilage can do permanent damage to the knee. Debris in the knee that causes a block may have to be removed surgically.