A shoulder labral tear involves damage to the fibrocartilage rim surrounding the shoulder socket, known as the glenoid labrum. This cartilage acts like a bumper, deepening the shallow socket and contributing significantly to shoulder stability. When this rim tears, it can lead to pain and a feeling of instability in the joint. While often associated with mechanical symptoms like clicking or catching, a labral tear can also be a direct source of nerve pain. The proximity of nerves to the shoulder joint means that damage or instability in the labrum can lead to nerve irritation or compression.
The Relationship Between Labral Tears and Shoulder Nerves
The labrum enhances the stability of the glenohumeral joint by increasing the surface area of the socket, keeping the head of the humerus securely in place. This stabilizing structure is intimately connected to surrounding nervous structures.
Major nerves, particularly the suprascapular nerve, run in close proximity to the shoulder joint capsule and the scapula bone. The suprascapular nerve provides both motor and sensory function to the rotator cuff muscles (supraspinatus and infraspinatus). Because it passes through narrow openings in the scapula, it is vulnerable to compression from related shoulder structures. Tears located in the superior or posterior aspects of the labrum are especially prone to affecting this nerve. For instance, a superior labrum anterior to posterior (SLAP) tear occurs near the nerve’s path, where the biceps tendon anchors to the top of the socket.
How Labral Damage Leads to Nerve Compression
Labral damage can irritate or compress adjacent nerves through distinct mechanical processes.
Traction or Tension
A labral tear often reduces joint stability, allowing the humeral head to shift excessively during movement. This abnormal movement can stretch nearby nerves, such as the suprascapular nerve, as they are pulled taut across bony landmarks.
Paralabral Ganglion Cyst
A labral tear can act like a one-way valve, allowing joint fluid to leak out and collect in the surrounding tissues. This fluid forms a cyst that can grow large enough to press directly on an adjacent nerve. Cysts arising from posterior labral tears commonly compress the suprascapular nerve in the spinoglenoid notch.
Direct Mechanical Impingement
The tear itself can also lead to direct mechanical impingement. Superior tears (SLAP lesions) occur near the nerve’s passage, and the torn flap of cartilage or associated inflammation can directly compress the nerve against the bone. Repairing the labral tear alone can sometimes resolve the compression by eliminating the source of instability or the cyst. These various forms of compression result in a condition known as suprascapular nerve entrapment.
Differentiating Nerve Pain from Joint Pain
The pain from a labral tear alone is described as a deep, dull ache within the shoulder, often accompanied by mechanical symptoms like clicking or popping sensations. This joint-related pain is usually localized to the shoulder itself.
Nerve involvement introduces a different set of distinctly neurological symptoms. The presence of radiating pain, where discomfort shoots down the arm or into the neck, is characteristic. Sensory changes include numbness or tingling (paresthesia) that follows the specific path of the irritated nerve.
Compression of the suprascapular nerve, which supplies motor function to the rotator cuff, leads to motor weakness. Patients may experience difficulty lifting the arm or performing external rotation. Over time, this weakness can progress to visible muscle wasting (atrophy) in the supraspinatus or infraspinatus muscles, indicating a chronic loss of nerve supply.
Treatment Focused on Nerve Relief
When nerve involvement is confirmed alongside a labral tear, treatment must address both the joint damage and the neurological irritation. Initial management includes rest, anti-inflammatory medications, and physical therapy. Physical therapy focuses on strengthening shoulder stabilizers to improve joint mechanics, reducing abnormal traction on the nerve.
If conservative approaches fail or severe compression is present, surgical intervention is required. The goal of surgery is twofold: to stabilize the shoulder and decompress the nerve. The surgeon repairs the torn labrum to eliminate instability or the mechanism leading to cyst formation. If a large ganglion cyst is pressing on the nerve, the procedure includes draining the cyst to immediately relieve pressure. For persistent nerve entrapment, the surgeon may also perform a formal nerve release to free the nerve from constricting ligaments or scar tissue. This combined approach ensures both the mechanical cause and the resulting neurological symptoms are addressed.