Infraspinatus tendinosis is a frequent source of shoulder discomfort, affecting a muscle located in the back of the shoulder blade. This condition involves the infraspinatus, one of the four muscles that form the rotator cuff, which stabilizes the shoulder joint. Tendinosis is a chronic issue defined by the progressive breakdown and degeneration of the tendon tissue, unlike short-term injuries. This distinction is important for understanding why specific treatments are needed for this long-term shoulder complaint.
Understanding the Infraspinatus Muscle and Tendinosis
The infraspinatus is a thick, triangular muscle situated on the posterior surface of the shoulder blade (scapula). Its tendon crosses the shoulder joint to attach to the top of the upper arm bone (humerus). The primary function of this muscle is to produce external rotation of the shoulder, which is the movement of turning the arm outward. It also works with the other rotator cuff muscles to hold the head of the humerus securely within the shoulder socket, maintaining joint stability.
The term tendinosis describes a chronic condition involving the non-inflammatory degeneration of the tendon’s collagen fibers. This is distinct from tendinitis, which implies acute inflammation of the tendon tissue. Tendinosis arises from repeated micro-tears that occur faster than the body can repair them. This leads to disorganized, thickened, and weakened tissue structure. Treatments focused solely on reducing inflammation are often less effective for tendinosis.
Primary Causes and Specific Symptoms
Infraspinatus tendinosis is caused by repetitive strain that places excessive mechanical load on the tendon over a prolonged period. Activities involving frequent overhead motion, such as throwing sports, swimming, or carpentry, repeatedly stress the tendon. Poor posture, particularly a rounded-shoulder position, can also contribute by altering shoulder joint mechanics and increasing friction. Age-related wear is a significant factor, as the tissue naturally weakens and loses its ability to regenerate over time.
Symptoms usually center on pain and weakness localized to the posterior shoulder. Patients often describe a deep, aching pain at the back of the shoulder that can sometimes radiate down the arm. This discomfort increases significantly when attempting activities requiring external rotation or reaching overhead. Pain at night is a common complaint, particularly when sleeping on the affected side due to tendon compression. The degeneration also leads to noticeable weakness when rotating the arm outwards against resistance.
How Medical Professionals Confirm the Diagnosis
Diagnosis relies on a thorough clinical assessment, including a detailed patient history and a physical examination of the shoulder joint. A medical professional will check for tenderness directly over the infraspinatus tendon’s insertion point on the humerus. They will also perform specific orthopedic tests designed to isolate the function of this muscle.
The Infraspinatus Test is a common physical assessment tool where the patient externally rotates their arm against the examiner’s resistance, often with the elbow bent to 90 degrees. A positive test, indicated by pain or reduced strength, strongly suggests an infraspinatus tendon problem. Imaging studies are used to confirm clinical findings and rule out other conditions. X-rays help eliminate bone-related issues, such as arthritis or fracture. Magnetic Resonance Imaging (MRI) is the most definitive tool for assessing soft tissues, as it confirms the structural degeneration, thickening, or small tears characteristic of tendinosis.
Non-Surgical Treatment and Recovery Protocols
Conservative management is the primary approach, focusing on halting the degenerative cycle and promoting tendon healing. Initial steps involve activity modification and relative rest, meaning the patient must avoid movements that aggravate the tendon. Non-steroidal anti-inflammatory drugs (NSAIDs) may be used for temporary pain relief, but long-term use is limited since inflammation is not the root cause. Corticosteroid injections are approached with caution, as repeated injections can potentially weaken the already compromised tendon structure.
Physical therapy is the foundation of recovery, involving a structured program of eccentric strengthening exercises. Eccentric exercises involve the slow, controlled lengthening of the muscle while under tension, which is thought to stimulate new collagen production and improves the tendon’s load-bearing capacity. For the infraspinatus, this means performing external rotation with a light resistance band or small weight, focusing on a slow, four-second return to the starting position. Consistency is crucial, as tendons heal slowly, sometimes requiring three to six months of dedicated rehabilitation. Surgery is reserved as a last resort for cases that fail to improve after six to twelve months of conservative treatment, or for full-thickness tendon tears.