Acromioclavicular joint disorders
- Scott M Koehler, MD
Scott M Koehler, MD
- Physician, Sports Medicine Specialist
- Allina Medical Clinic, Northfield
- Section Editor
- Karl B Fields, MD
Karl B Fields, MD
- Editor-in-Chief — Primary Care Sports Medicine (Adolescents and Adults)
- Section Editor — Biomechanics, Rehabilitation, and Recovery; Sports-Related Injuries; Symptom Assessment and Physical Examination
- Professor of Family Medicine and Sports Medicine
- University of North Carolina at Chapel Hill
Acromioclavicular (AC) joint disorders can be classified into acute injuries, repetitive strain injuries, degenerative conditions, and other conditions. The diagnosis of acute AC joint injury (sometimes referred to as a sprain or "separated" shoulder) is often straightforward due to the presence of focal tenderness, swelling, and deformity.
AC joint disorders from overuse, inflammation, or chronic degeneration can be more difficult to diagnose, particularly if concomitant shoulder problems exist. This topic will review the evaluation and management of AC joint disorders. AC joint injuries are discussed separately. (See "Acromioclavicular joint injuries (“separated” shoulder)".)
ANATOMY AND PATHOPHYSIOLOGY
The acromioclavicular (AC) joint unites the distal clavicle and the acromion of the scapula. It contains an intra-articular disc, a synovial membrane, and articular cartilage that cover the distal end of the clavicle and the opposing surface of the acromion . The AC joint is supported by a ligament complex, as well as surrounding fascia and muscles (picture 1). The anatomy and biomechanics of the AC joint are described in greater detail separately. (See "Acromioclavicular joint injuries (“separated” shoulder)", section on 'Anatomy and biomechanics'.)
The AC joint normally degenerates over several decades but in most cases, remains asymptomatic. The joint gradually narrows as the articular disc and chondral cartilage wear away. This degeneration is often more rapid than in other joints, with the articular disc beginning to break down in the second decade of life . By the age of 40, most patients have narrowing of the joint space and possibly other degenerative findings .
EVALUATION OF THE PAINFUL AC JOINT
The patient with a painful acromioclavicular (AC) joint often complains of focal shoulder pain, and when asked to point to the most painful spot typically indicates the top of the shoulder. However, pain arising from the AC joint may be more generalized since the joint is innervated by branches of both the axillary and lateral pectoral nerves. Symptoms arising from the AC joint may be felt anywhere from the base of the neck and trapezius region to the lateral deltoid .
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- ANATOMY AND PATHOPHYSIOLOGY
- EVALUATION OF THE PAINFUL AC JOINT
- - Inspection
- - Palpation
- - Shoulder range of motion
- - Neurovascular function
- - Special maneuvers for the AC joint
- Cross body adduction test
- AC shear testing
- Active compression test
- Diagnostic imaging
- - Plain radiographs
- - Bone scan
- - Ultrasound
- - Magnetic resonance imaging
- Diagnostic injection
- DIAGNOSTIC APPROACH
- SPECIFIC DISORDERS
- Acromioclavicular joint injuries
- Overuse injuries
- Osteolysis of the distal clavicle
- Painful degeneration of the AC joint
- Other conditions
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS