Knee locking describes a sensation where the knee joint unexpectedly becomes stuck, making it difficult or impossible to fully straighten or bend the leg. This experience can range from a fleeting, momentary catch to a complete inability to move the joint, significantly impacting daily activities like standing, sitting, or walking. The feeling often arises suddenly and can be quite alarming for individuals.
Distinguishing True from Pseudo Knee Locking
Understanding knee locking involves differentiating between two distinct mechanisms: true locking and pseudo locking. True knee locking occurs when a physical obstruction within the joint prevents normal movement, leading to a mechanical block. This results in a “hard stop” where the knee physically cannot extend or flex beyond a certain point.
Conversely, pseudo knee locking, also referred to as false locking, is a sensation of the knee getting stuck without a physical blockage. This feeling is triggered by severe pain, muscle spasms, or general stiffness around the knee. While movement is restricted and painful, the knee joint remains physically capable of moving, and the sensation can sometimes be overcome with gentle effort or by changing position. Pseudo locking acts as a protective mechanism, restricting movement to prevent further pain or potential damage.
Specific Causes of Knee Locking
True knee locking stems from mechanical issues within the joint. Common causes include meniscal tears, especially “bucket handle” tears where a torn cartilage piece flips into the joint space, physically blocking movement, often from forceful knee twisting. Another cause is “loose bodies,” small bone or cartilage fragments that break off and float within the joint, impeding motion when wedged between joint surfaces. A torn anterior cruciate ligament (ACL) remnant or osteochondritis dissecans, where cartilage and underlying bone detach, can also create such an obstruction.
Pseudo knee locking is linked to conditions causing pain, inflammation, or muscle dysfunction around the knee. Patellofemoral pain syndrome, characterized by pain around the kneecap, can lead to muscle guarding or spasms that create a locking sensation. Plica syndrome, involving inflammation of a fold in the knee joint tissue, can also cause pain, clicking, and a temporary catching sensation. Severe osteoarthritis contributes to pseudo locking through joint stiffness, bone spurs, and inflammation, limiting motion and causing a painful catching feeling. Muscle spasms in the quadriceps or hamstrings can restrict knee movement, mimicking a locked sensation, and conditions like iliotiberal band friction syndrome can lead to muscle guarding around the knee.
What to Do When Your Knee Locks
When experiencing knee locking, avoid forcing the knee to move. Instead, gently attempt to release the lock by wiggling the leg or performing slight, controlled movements. Resting and elevating the knee can help reduce discomfort. Applying ice to the affected area may alleviate pain and swelling. Over-the-counter pain relievers, such as ibuprofen, can also manage pain and inflammation.
Seek medical attention if knee locking is persistent and cannot be released, or if accompanied by severe pain, inability to bear weight, significant swelling, or a noticeable deformity. Recurrent episodes also warrant professional evaluation. A healthcare provider can diagnose the underlying cause through physical examination and imaging tests like X-rays or MRI scans. Treatment approaches vary depending on the diagnosis and may include rest, physical therapy to strengthen surrounding muscles and improve mobility, or pain management strategies. In some cases, particularly for true mechanical locking, surgical intervention may be considered to remove the obstruction or repair damaged tissues.