Tendons are dense, cord-like structures that serve as the mechanical bridge between muscle and bone. Their primary function is to transmit the force generated by muscle contraction, allowing for movement of the skeletal system. Tendons are composed mainly of collagen fibers, giving them great tensile strength to withstand significant loads. When people experience an unusual sensation of a body part shifting, they often wonder if these tissues can actually slip out of their normal position.
Anatomical Reality of Tendon Displacement
A tendon is held securely in place by surrounding anatomical structures, preventing it from straying during movement. These stabilizing restraints often include fibrous bands of tissue called retinacula, or a smooth, bony channel known as a tendon groove. When a tendon moves out of its normal path, the condition is referred to as tendon subluxation (partial sliding) or, if displacement is complete, a dislocation. Subluxation often involves the tendon snapping back into place immediately.
Tendon displacement is concentrated in areas under high mechanical stress. The ankle is a common site, where the peroneal tendons run behind the outer ankle bone, stabilized by the superior peroneal retinaculum. Similarly, the long head of the biceps tendon, which travels through a groove at the front of the shoulder, is held in place by the transverse humeral ligament, making it susceptible to displacement.
Common Causes of Tendon Subluxation
The fundamental cause of tendon subluxation is the failure of the tissue restraint that normally secures the tendon in its location. Acute trauma is the most frequent trigger, particularly sudden, forceful movements that overload the joint. A severe ankle sprain, for instance, can violently stretch and tear the superior peroneal retinaculum, causing the peroneal tendons to slip out of the groove.
Structural or congenital factors can also predispose individuals to this issue. Some people are born with a bony groove that is too shallow to contain the tendon securely, meaning even a minor injury can initiate instability. Over time, chronic strain or repetitive microtrauma can also degrade the restraining tissues, weakening the sheath until the tendon begins migrating out of position during specific actions.
Recognizing the Symptoms
The defining characteristic of tendon subluxation is a distinct mechanical sensation felt during joint movement. Patients frequently report a noticeable “snapping,” “popping,” or “clicking” on the side of the affected joint, which represents the tendon sliding out of its channel and then back in. This sensation is often reproducible when the joint is moved through a specific range of motion, such as turning the foot outward against resistance in the ankle.
This mechanical symptom is accompanied by localized pain, which can be sharp when the tendon slips or a dull ache that persists afterward. Swelling and tenderness are often present along the path of the tendon, indicating inflammation from repeated friction. Because the displacement occurs only during certain movements, the symptoms may be intermittent. Any persistent snapping or popping associated with pain or instability warrants a medical evaluation to prevent further damage.
Medical Interventions and Recovery
Initial management for acute tendon subluxation begins with non-surgical methods aimed at reducing inflammation and allowing the damaged restraint to heal. The RICE protocol is commonly employed, involving rest, ice to minimize swelling, compression, and elevation of the limb. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be recommended to help manage pain and local inflammation.
Immobilization is a common next step, using a cast or specialized boot to hold the joint in a neutral position for several weeks, often four to six, to allow the torn retinaculum to heal without tension. Following this period, physical therapy is initiated to restore muscle strength and joint stability. Rehabilitation focuses on strengthening the muscles that support the affected area and improving proprioception (the body’s sense of joint position).
If non-surgical treatment fails, or if the subluxation is severe and chronic, surgical intervention may be necessary. The goal of surgery is to recreate a stable pathway that prevents the tendon from slipping out again. In the ankle, this often involves repairing or reconstructing the superior peroneal retinaculum, reattaching it securely to the bone.
In cases where a structural problem is present, a bony procedure may be performed to deepen the shallow groove where the tendon sits, providing a more secure containment. For the biceps tendon in the shoulder, procedures like tenodesis may be used to re-anchor the tendon to the bone in a more stable location. Post-operative recovery typically involves a period of non-weight-bearing immobilization, often in a cast or boot for about four weeks, followed by an extensive rehabilitation program lasting several months, with a return to sports activities expected around three months after the procedure.