Knee pain described as “locking” occurs when the joint feels stuck. This symptom refers to the knee’s inability to fully extend or bend.
What Does Knee Locking Mean?
The term “knee locking” can refer to two distinct sensations: true locking and pseudo-locking. True locking occurs when a physical obstruction within the knee joint mechanically prevents its full range of motion, making it impossible to completely straighten or bend the leg.
In contrast, pseudo-locking, sometimes called false locking, describes a feeling of the knee catching or giving way, often due to pain, muscle spasm, or swelling. While the individual experiences an inability to move the knee, there is no mechanical block impeding movement; discomfort or muscle guarding prevents full motion.
Primary Causes of Pain When the Knee Locks
Several conditions can lead to knee pain accompanied by a locking sensation, each with a distinct mechanism. These issues typically involve damage or displacement of structures within or around the knee joint.
Meniscus tears are a frequent cause of true knee locking. The menisci are C-shaped pieces of cartilage that act as shock absorbers between the thighbone and shinbone. If a meniscus tears, a fragment can become displaced and get caught in the joint space, physically blocking the knee’s movement. This can happen with forceful twisting or rotation of the knee, or due to gradual wear and tear. A specific type, the “bucket-handle tear,” is known for causing mechanical locking.
Loose bodies within the knee joint can also cause true locking. These are fragments of bone or cartilage that have broken off and float freely in the joint space. Such fragments can result from injuries, degenerative conditions like osteoarthritis, or even previous surgeries. When these loose bodies become wedged between the joint surfaces, they obstruct normal movement and lead to locking and pain.
Patellar subluxation or dislocation involves the kneecap (patella) temporarily shifting out of its normal alignment. When the kneecap moves out of place, it can create a sensation of the knee locking or giving way, often associated with pseudo-locking due to pain or instability. This condition can stem from trauma, weak ligaments, or issues with how the kneecap tracks in its groove.
Plica syndrome occurs when a fold of the synovial membrane lining the knee joint becomes irritated or inflamed. If a plica, especially the medial plica, becomes thickened or inflamed, it can get pinched between the kneecap and thighbone. This pinching can cause pain, clicking, and a sensation of catching or pseudo-locking, especially during repetitive knee movements or after an injury.
Osteoarthritis, a degenerative joint disease, can also contribute to a sensation of knee locking. As cartilage wears away, bone spurs may form, and small fragments of bone or cartilage can break off, acting as loose bodies. While often causing pseudo-locking due to inflammation, stiffness, and pain, advanced arthritis can sometimes lead to mechanical obstruction if bone spurs or debris interfere with joint motion.
When to Consult a Doctor
Seeking medical attention for knee pain accompanied by locking is advisable, particularly when certain symptoms are present. Prompt evaluation can help identify the underlying cause and prevent further complications.
Consult a healthcare professional if you experience an inability to bear weight on the affected leg, severe pain, or swelling. Immediate medical attention is also warranted for a visible knee deformity, numbness or tingling below the knee, or redness, warmth, or fever around the knee.
Frequent or persistent knee locking that doesn’t resolve should be assessed by a doctor. Medical consultation is also necessary if locking occurs with a popping sound at the time of injury, or if you cannot fully straighten or bend the knee after an incident.
Managing and Treating Knee Locking
Once a diagnosis is established, various strategies can manage and treat knee pain associated with locking. The approach depends on the underlying cause and severity of the condition.
Conservative management is often the initial course of action. This includes rest for the affected knee, applying ice to reduce swelling and inflammation, and using compression with a bandage. Elevating the leg can also help decrease fluid buildup. Over-the-counter pain relievers, such as non-steroidal anti-inflammatory drugs (NSAIDs), may be recommended to manage pain and inflammation.
Physical therapy plays a role in rehabilitation, focusing on strengthening the muscles around the knee, improving flexibility, and enhancing joint stability. A tailored exercise program helps redistribute forces across the joint and can alleviate the locking sensation. Activity modification, which involves adjusting movements to reduce stress on the knee, is also a common recommendation.
For some conditions, medical interventions like injections may be considered. Corticosteroid injections can help reduce inflammation and pain, particularly in cases where inflammatory processes contribute to pseudo-locking. Hyaluronic acid injections might be used to improve joint lubrication, especially in arthritis-related cases.
Surgical options are considered when conservative treatments are ineffective or if a mechanical obstruction causes true locking. Arthroscopy, a minimally invasive procedure, is commonly performed to address issues like meniscus tears, where torn cartilage can be repaired or trimmed. Loose bodies can also be removed arthroscopically. Plica excision may be performed if an inflamed plica is the cause of the locking.