Shoulder subluxation refers to a partial displacement of the upper arm bone (humerus) from the shoulder socket (glenoid). The humeral head slips out of its normal position but does not fully separate, distinguishing it from a complete dislocation. This condition signals instability within the joint and can be an uncomfortable and often painful injury.
The Shoulder Joint Explained
The shoulder is a complex ball-and-socket joint, the glenohumeral joint, allowing for an extensive range of motion. The “ball” is the humeral head, and the “socket” is the shallow glenoid fossa of the scapula. This shallow design provides mobility but compromises stability, making it the most mobile joint in the human body.
Stability in the shoulder joint depends on surrounding soft tissues rather than bony structures. The rotator cuff, a group of four muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) and their tendons, provides dynamic stability. These muscles keep the humeral head centered within the glenoid socket during arm movements. Ligaments, the joint capsule, and the glenoid labrum, a fibrocartilaginous rim, also reinforce the joint.
How Subluxation Occurs and What It Feels Like
Shoulder subluxation often results from trauma or repetitive stress. Common causes include falls onto an outstretched arm, sudden impacts, or sports injuries, especially those involving overhead movements like throwing. Repetitive motions can gradually loosen the shoulder capsule and supporting structures, leading to instability and making the joint more prone to partial displacement. Muscle weakness, such as after a stroke, can also contribute.
When a subluxation occurs, individuals feel immediate pain and a sensation of the shoulder “slipping out” or “giving way.” There may be a temporary inability to move the arm, accompanied by weakness or a “dead arm” sensation. A popping or clicking sensation within the joint can also occur. While acute subluxations result from a single event, recurrent instances lead to chronic instability.
Identifying and Addressing Subluxation
Diagnosing shoulder subluxation involves a physical examination. The healthcare provider assesses the shoulder’s range of motion, stability, and tenderness. They perform specific tests to evaluate for looseness or displacement of the humeral head. Comparing the affected shoulder to the unaffected side is also part of the assessment.
Imaging tests are used to confirm the diagnosis and rule out other injuries. X-rays identify fractures or dislocations. Magnetic Resonance Imaging (MRI) provides detailed soft tissue images, detecting injuries to ligaments, tendons, or the labrum, which often accompany subluxations. Initial management includes rest, applying ice to reduce swelling and pain, and immobilizing the arm in a sling. Pain medication may also be prescribed.
Paths to Recovery and Future Protection
Recovery from a shoulder subluxation involves a structured rehabilitation program. Physical therapy plays a central role, focusing on exercises designed to strengthen the rotator cuff muscles. Strengthening these muscles helps to improve shoulder stability and control, crucial for preventing future partial displacements. Exercises may include isometric contractions, range of motion drills, and progressive resistance training.
Patients are guided through rehabilitation phases, gradually increasing activity as the shoulder heals and regains strength. Modifying activities and sports techniques also reduces re-injury risk, especially for those in overhead sports. While many subluxations respond well to non-surgical approaches, surgical intervention is considered for recurrent instability, particularly with significant soft tissue damage or bone loss. The aim is to repair damaged structures and restore long-term stability.