Joint locking (symptom)

What is Joint Locking?

"Joint Locking" or "Locked Joint" is the term used to describe the pain that is caused when the joint is extended beyond a certain angle. As a result, the patient may be forced to restrict the joint extension from movement limited to just 10 to 30 degrees. Any further extension beyond the restricted angle can cause severe intractable joint pain. Limitation in achieving a normal extension can create many challenges for a normal movement.^[1] Joint locking is most commonly caused due to meniscus tear or similar injuries, osteoarthritis and congenital defects in a few cases.^[2]

Causes^[1][2]

Joint Locking is caused by mechanical obstruction of joint movements. There can be several reasons that can cause a mechanical block.

• Bone Fragments or Cartilage that are physically caught within the joint can cause Joint Locking.
• Meniscus Tear - Causes restriction of joint extension and is one of the main reasons for joints to get locked up.
• Fracture of Tibia or Fibula at the joint can cause a joint to lock up.
• Complications after surgery – post-surgical complications can cause joint locking. For instance, an anterior cruciate ligament reconstruction can sometimes cause joint locking despite an otherwise successful surgery outcome.
• Osteoarthritis - Locked joint in patients who have arthritis can cause severe pain because of restricted joint extension. Natural aging and arthritis can increase the risk for joint locking up. Over time, the cartilage that surrounds the bones in the joint can wear out and begin to break off.
• Ligament Injury as a Cause for Joints to get Locked Up- Ligament injury causes unstable joint and joint giving way; a condition sometimes referred to as a trick joint. Joint pain becomes severe with extension and weight bearing.
• Loose Tissue Fragments - Severe pain can result from loose tissue fragments (cartilage, fragments of torn meniscus) when lodged inside the joint and makes the joint locked up.
• Inflammation of Joint - Joint inflammation causes swelling of the joint. Swelling and edema of joint restricts extension and causes pain leading to muscle spasm and locked joint.
• Dislocation of Patella - Superior dislocation of the patella can cause restriction of joint extension and severe pain with extension restricting joint movements and causing the joints to get locked up.
• Tear of Mediopatellar Plica - Joint synovitis causes mechanical damage of plica inside the joint resulting in severe pain and limited extension of the joint causing locked joint.
• Osteochondritis Dissecans - Joint cartilage is completely worn out, which is then followed by a fragment of chipped bone to dislodge in joint. The condition restricts movements of joint and causes severe pain along with locked joint.^[3][4]

Pathophysiology of Joint Locking^[2]

Joints are composed of:

• Cartilages - Medial and Lateral Meniscus.
• Ligaments - Anterior and Posterior Cruciate Ligaments.
• Synovial Membrane.
• Bones - Distal end of the femur and the proximal end of the tibia.

Joint locking is a condition caused by inflammation of synovial membrane, cartilage damage, ligamental tear or fracture of the patella, tibia or fibula. Space within the joint is limited and thin. Trauma, injury, and disease causing a hematoma, inflammation of synovial membrane within the joint can compromise the joint space and restrict the joint extension. ^[1]

Extension and flexion of joint depend on the alignment of medial and lateral meniscus as well as the stability of anterior and posterior ligament. Joint during flexion and extension maintains an optimum horizontal or oblique vertical position of the meniscus. Tear of meniscus or fragments within joint interferes with achieving an optimum resting position in the extension of the joint.^[3]

The joint has two tough cartilaginous menisci. Medial meniscus lies inside of the joint and lateral meniscus lies outside of joint. Both menisci lie between femur and tibia. Meniscus tear causes a large fragment of the torn meniscus to become wedged within the joint. A torn meniscus fragment obstructs the extension of the joint by locking the joint and prevents normal movement.^[3]

A misalignment of the muscles or bones due to muscle strain or an injury can also cause joints to lock. In either situation, the joint can become stiff and frozen, which is accompanied by extreme pain. An effective treatment of joint locking requires that the initial symptoms that caused it are known.

Signs and Symptoms^[1]

• Fever: Joint infection or abscess
• Severe Pain while joint extension is one of the symptoms of locked joint
• Restricted Joint Movements: Joint Locking often causes difficulty to stand on the affected leg.
• Joint Examination: Tender and painful joint on palpation.
• In the Locked joint, Flexion of Joint is fixed in position, often at a 45-degree angle.
• Extension of Joint: Person suffering from joint locking is unable to straighten the leg. The leg can be cautiously and manually placed to complete extension position using both hands.
• Joint movement creates a sound because of the rubbing of the fragment of torn meniscus. This rubbing sound is associated with severe pain.
• Stump Impingement Reflex Sign (a specific sign for ACL stump impingement as a cause of knee locking) is observed in anterior cruciate ligament tear.

Investigations to Diagnose Joint Locking^[2]

X-Rays to Diagnose the Cause of Joint Locking:

X-rays are useful in diagnosing degenerative arthritis in the joint which could be the cause for joints to get locked.

MRIs (magnetic resonance imaging)

MRIs are useful in diagnosis of following disease which can be causing the joints to get locked:

• Meniscus tear.^[5]
• Fracture or dislocation of the cruciate ligament.
• Fracture or dislocation of the patella.
• Fracture of tibia or fibula at the joint.

Blood Examination:

• WBC Count - Increased white blood cell count in case of joint infection.
• Rheumatoid Factor is elevated in a patient suffering from rheumatoid arthritis (RA).
• Elevated ESR (Erythrocyte Sedimentation Rates) - Seen in rheumatoid arthritis and inflammatory arthritis.
• Elevated Uric Acid levels in the blood may indicate gout.^[3]

Treatment^[2]

• NSAIDs (non-steroidal anti-inflammatory drugs) - Anti-inflammatory medications are prescribed for inflammation, pain, and fever associated with joint locking.
• Muscle Relaxants are prescribed to ease joint pain, reduce joint stiffness and relax muscles.
• Heat and Cold Application.
• Physiotherapy for Locking Joint – Physiotherapy is directed towards exercise, stretching, massage and joint manipulations.

Surgery of Locked Joint:

• Removal of Fragments in Joint that cause joint locking. Torn cartilage is removed so it no longer interferes with joint mobility.
• Meniscectomy: This is done to eliminate all parts of torn meniscus that can cause joints to get locked up.
• Meniscus Repair Surgery: It is an arthroscopic surgical procedure^[6] to repair torn joint cartilage that can be causing the joints to get locked
• Meniscus Transplantation.
• Joint Replacement.^[7]

References