Acromioclavicular Joint Osteoarthritis

The shoulder complex consists of several joints that work together to provide exceptional range of motion:

• The glenohumeral joint (ball-and-socket joint) between the upper arm bone (humerus) and shoulder blade (scapula).
• The acromioclavicular (AC) joint, where the collarbone meets the acromion.
• The sternoclavicular joint, connecting the collarbone to the breastbone (sternum).
• The scapulothoracic articulation, which allows the shoulder blade to glide smoothly on the rib cage.

The AC joint is lined with cartilage that enables smooth motion and is supported by strong ligaments that maintain stability. When the cartilage deteriorates, the bones of the clavicle and acromion come into direct contact, causing pain and inflammation. Bone spurs may also develop, further limiting motion.

The AC joint is one of the most common locations to develop osteoarthritis, especially in individuals over 40 years old or those who perform repetitive heavy lifting. Studies suggest that up to 50% of adults over age 50 show x-ray signs of AC joint arthritis, but most have minimal symptoms.

However, pain sometimes becomes clinically significant when the joint space narrows and bone spurs irritate surrounding tissues, such as the rotator cuff or subacromial bursa. In younger athletes, repetitive micro-trauma from bench pressing, push-ups, or contact sports can lead to premature arthritis.

Common symptoms include:

• Pain on the top of the shoulder, particularly over the AC joint.
• Tenderness when pressing on the joint or carrying objects.
• Pain with cross-body motion, such as reaching across the chest or overhead.
• Clicking or popping sensations when moving the arm.
• Decreased range of motion or stiffness, especially in the morning.
• Pain at night when lying on the affected side.

In advanced cases, bone spurs from the AC joint may impinge on nearby tendons, causing rotator cuff irritation or bursitis.

Diagnosis begins with a thorough evaluation by Dr. José Vega, Cleveland’s trusted shoulder specialist. During your visit, he will review your medical history, occupation, and activity level, followed by a focused physical examination of the shoulder.

Physical exam findings may include:

• Localized tenderness directly over the AC joint.
• Pain with the cross-body adduction test (moving the arm across the chest).
• Reproduction of symptoms with overhead motion or internal rotation.

Imaging studies confirm the diagnosis:

• X-rays show joint space narrowing, bone spurs, and cystic changes.
• MRI evaluates cartilage loss and associated conditions such as rotator cuff tendinitis or impingement.
• Diagnostic injections—a small amount of numbing medication injected into the AC joint—can help confirm the joint as the true source of pain.

Treatment focuses on relieving pain, restoring function, and allowing patients to return to normal activities.

Nonsurgical Treatment

Most patients respond well to conservative care:

• Activity modification: Avoiding repetitive overhead or cross-body movements that aggravate symptoms.
• Physical therapy: Focused exercises to strengthen the rotator cuff and scapular stabilizers, improving shoulder mechanics.
• Anti-inflammatory medications (NSAIDs): Reduce pain and swelling.
• Ice therapy: Helps control inflammation after activity.
• Corticosteroid or biologic injections (PRP): Can provide temporary pain relief and decrease inflammation.

These treatments often provide lasting relief for mild to moderate arthritis.

Surgical Treatment

If pain persists despite nonsurgical management and significantly limits function, surgery may be considered.

The most common procedure is an arthroscopic distal clavicle excision (also called the Mumford procedure):

• The surgeon removes 5–8 mm of the outer end of the clavicle, eliminating bone-on-bone contact at the AC joint.
• This is performed arthroscopically through small incisions, often combined with subacromial decompression or rotator cuff treatment if needed.
• Patients typically go home the same day, begin gentle motion within days, and regain full function within 6–8 weeks.

This procedure provides excellent long-term pain relief and restores comfort for overhead activities without compromising shoulder strength.