In medicine, joint locking is a symptom of pathology in a joint. It is a complaint by a person when he is unable to fully flex or fully extend a joint. This term is also used to describe the mechanism of lower limb joints held in full extension without much muscular effort when a person is standing.
Video Joint locking (medicine)
Clinical symptom
Complaint of locking sensation in the knee joint can be divided into true locking and pseudolocking. True locking happens when the intra-articular structure (e.g. ligaments) is damaged, or there is the presence of loose body inside the joint, or there is a meniscal tear. The knee can be unlocked by rotating the leg and full movment can be restored. A person may felt the presence of loose body in the suprapatellar region, or lateral and medial gutter. Once the loose bodies is felt, it would slide and move to other area, thus it is also termed as "joint mouse".
Pseudolocking usually happens when when a person feels pain when trying to flex or extend a knee joint while there is no structural causes of the locking. The locking is usually relieved after massage or taking painkillers.
Joint locking is a common symptom of:
- Osteoarthritis
- Osteochondritis dissecans
- Synovial osteochondromatosis
- Tear of meniscus of the knee
- Anterior cruciate ligament injury of the knee
Maps Joint locking (medicine)
Locking mechanism
Locking of the knee happens during the last stages of extension when a person is standing up. Medial rotation of femur occurs as the space available at the lateral condyle of tibia is being used up by the lateral condyle of femur during extension. Therefore, lateral femoral condyle acted as an axis for medial femoral condyle to rotate backwards. This movement is aided by oblique pull of the ligaments of the knee joint and contraction of the quadriceps muscles. The ligaments are pulled taut when the knee joint is locked in place during standing. When the knee is flexed, it is unlocked by the popliteus muscle through the lateral rotation of femur.
The locking mechanisms of hip joint and midtarsal joint are also being investigated in cadavers.
References
Source of the article : Wikipedia
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