Shoulder Subluxation After Stroke: Causes & Treatment

Introduction to Hemiplegic Shoulder Subluxation

Following a stroke, motor deficits can affect various parts of the body, but the shoulder joint is particularly vulnerable to secondary complications. The shoulder (glenohumeral joint) is the most mobile joint in the human body, relying heavily on active muscle support rather than deep bony sockets for its stability. When a stroke paralyzes the muscles surrounding this joint, the structural integrity is compromised.

This leads to hemiplegic shoulder subluxation—a partial dislocation where the head of the humerus (upper arm bone) slips out of the glenoid fossa (shoulder socket). This condition affects up to 80% of stroke patients who have severe upper limb paralysis. Preventing and managing a shoulder subluxation stroke complication requires strict adherence to clinical positioning guidelines and specialized physiotherapy.

Pathophysiology: Why the Shoulder Dislocates After Stroke

To understand why subluxation occurs, we must look at the anatomical stabilizers of the shoulder. Under normal conditions, the shoulder is held in place by the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) and the deltoid muscle, which act as active tension bands.

The Flaccid Stage

Immediately after a stroke, during the flaccid stage of hemiplegia, the muscles of the affected arm are completely limp and devoid of tone. Without muscular contraction, the weight of the arm acts as a continuous downward pulling force. Over time, gravity stretches the passive structures—the joint capsule and ligaments—allowing the humerus to drop. The supraspinatus muscle, which is the primary stabilizer preventing downward displacement of the humerus, is particularly susceptible to stretching and atrophy.

The Spastic Stage

As the patient transitions to the spastic stage of recovery, high muscle tone can develop in the shoulder adductors and internal rotators (such as the pectoralis major and latissimus dorsi). This spasticity pulls the shoulder inward and downward, further malaligning the joint and causing severe hemiplegic shoulder pain.

Clinical Signs and Assessment

Shoulder subluxation is diagnosed through physical examination and can be confirmed with X-rays if necessary:

• The Finger-Breadth Test: Clinicians palpate the gap between the acromion (the bony tip of the shoulder) and the head of the humerus. Subluxation is commonly graded as a 1-finger, 2-finger, or 3-finger gap.
• Visible Deformity: The shoulder appears flattened or dropped compared to the unaffected side, and the arm hangs limply with the palm turned backward.
• Localized Pain: Although subluxation itself is not always painful initially, the chronic stretching of the joint capsule and brachial plexus nerves leads to severe, burning shoulder pain, especially during movement.

Clinical Care Guidelines and Prevention

Preventing subluxation is far easier than reversing it once the joint capsule has been permanently stretched. The following guidelines are critical for caregivers and clinical staff:

Safe Patient Handling: The Golden Rule

NEVER pull on a stroke patient's affected arm during transfers, repositioning in bed, or when helping them stand. Pulling on a flaccid arm exerts immense force on the unsupported joint, causing immediate subluxation, nerve traction injuries, and rotator cuff tears.

Supportive Positioning

• In Bed: The affected arm should be supported on pillows in front of the body, with the elbow slightly bent and the hand elevated to prevent swelling.
• In a Wheelchair: Use a lapboard, arm trough, or specialized tray to keep the arm supported at elbow height, preventing it from hanging down.
• When Standing: The arm should not hang unsupported. If the patient has no voluntary control, a supportive sling should be worn when walking or standing.

Comparison of Shoulder Support Slings

| Sling Type | Design Mechanism | Advantages | Disadvantages | | :--- | :--- | :--- | :--- | | GivMohr Sling | Harness system supporting the hand, wrist, and elbow | Supports joint alignment without restricting arm movement or promoting abnormal posturing | Complex to put on; requires training for caregivers | | Standard Hemi-Sling | Holds the forearm across the chest in a pouch | Simple to apply; effectively unloads the weight of the arm | Promotes a closed, flexed posture; encourages neglect of the limb; limits functional use | | Humeral Cuff Sling | Cuff around the humerus connected to a chest strap | Directly pulls the humerus upward; leaves the elbow and hand free | Can slip down; less support for the wrist and fingers |

Evidence-Based Physiotherapy Interventions

Rehabilitation focuses on activating the stabilizing muscles and protecting the joint during movement:

1. Functional Electrical Stimulation (FES / NMES)

FES is the gold standard physical therapy intervention for early subluxation. Electrodes are placed over the supraspinatus and posterior deltoid muscles. The electrical pulses trigger contractions in these muscles, pulling the humeral head back into the socket. Clinical trials indexed on PubMed show that early application of FES during the flaccid stage significantly reduces the severity of subluxation.

2. Scapular Mobilization and Alignment

The shoulder blade (scapula) must move in coordination with the arm. If the scapula is stuck in downward rotation (common after stroke), raising the arm will cause mechanical impingement. Therapists perform passive scapular mobilization to restore normal movement before attempting to move the arm.

3. Progressive Muscle Strengthening

As voluntary movement returns, therapists guide patients through active-assisted exercises, progresses to gravity-eliminated movements (such as moving the arm on a powder board), and finally to resistive training to rebuild the rotator cuff and deltoid muscles.