Knee locking is a sensation where the knee joint suddenly becomes stuck, making it difficult or impossible to bend or straighten the leg. This can be unsettling and painful, often interrupting daily activities. The term encompasses different sensations and underlying causes, making understanding these distinctions important.
How Knee Locking Feels
The experience of a locked knee can manifest in different ways, broadly categorized into “true locking” and “pseudo-locking.” True locking occurs when a physical obstruction within the knee joint prevents full movement, causing the knee to get stuck. This might feel like something is catching or jamming the joint, making it impossible to fully extend or flex the leg. When the obstruction is released, there might be a noticeable pop or click, and movement can return.
Pseudo-locking is not due to a mechanical blockage but results from pain, muscle spasms, or inflammation that inhibits movement. In this scenario, the knee feels stuck, but it can often be moved with effort, though doing so may cause significant pain. Accompanying sensations for either type of locking can include stiffness, a feeling of instability, or the knee giving way. Swelling around the knee joint is also a common symptom, especially in cases involving inflammation or injury.
Why Knees Lock
Knees lock due to various underlying issues that disrupt the joint’s smooth operation.
One common cause is a meniscus tear, where a piece of the C-shaped cartilage that cushions the knee joint can tear and get caught between the bones, physically blocking movement. This can happen from a forceful twisting motion of the knee or from age-related degeneration. A specific type, known as a “bucket handle tear,” is particularly prone to causing true locking.
Loose bodies within the joint are another frequent culprit. These are fragments of bone or cartilage that break off due to injury, degeneration, or certain conditions, and then float freely in the joint fluid. When these fragments become lodged between the moving parts of the knee, they can cause a sudden, sharp locking sensation. These loose bodies can vary in size and may result from conditions like osteoarthritis or direct trauma.
Issues with the kneecap, or patella, can also lead to a locking sensation. Conditions like patellar subluxation or dislocation, where the kneecap partially or completely slips out of its normal groove, can cause the knee to feel like it’s catching or locking. This occurs because the kneecap’s abnormal movement interferes with the smooth bending and straightening of the knee.
Arthritis, particularly osteoarthritis, can contribute to knee locking. As the cartilage in the knee wears down, bone spurs (osteophytes) can form along the edges of the joint. These bony growths can interfere with joint movement, leading to a catching or locking sensation, especially when the knee is bent or straightened. Inflammation associated with arthritis can also cause pseudo-locking due to pain and muscle guarding.
What To Do When Your Knee Locks
When your knee locks, there are immediate steps you can take to manage the situation. Gently attempting to extend or flex the knee can sometimes help dislodge whatever is causing the mechanical blockage. However, it is important to avoid forcing the movement, as this can cause further injury. Applying ice to the affected knee can help reduce swelling and discomfort, and resting the leg by elevating it can also be beneficial.
Seeking medical attention is advisable, especially if the knee locking is persistent, accompanied by severe pain, or if you are unable to bear weight on the leg. Significant swelling or any visible deformity of the knee are also signs that require professional evaluation. These symptoms suggest a potentially serious underlying issue that requires diagnosis.
A healthcare provider will perform a physical examination to assess the knee’s range of motion and tenderness. They may also order imaging tests, such such as X-rays to check for bone fragments or arthritis, or an MRI to visualize soft tissues like cartilage and ligaments. These diagnostic tools help determine the specific cause of the knee locking.