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Shoulder

AC Joint Osteoarthritis

Acromioclavicular (AC) joint osteoarthritis is a common condition where the cartilage in the small joint above the shoulder joint wears down over time. This leads to pain, stiffness, and difficulty with shoulder movement—especially during overhead activity, weightlifting, or sleeping on the affected side. AC joint osteoarthritis can occur as a result of normal aging, prior injuries, or overuse.

Fortunately, most patients can manage symptoms with nonoperative treatments such as physical therapy, medications, and activity modification. In cases where pain is severe or unresponsive to conservative care, surgery may be recommended to relieve symptoms and restore function.

The shoulder is made up of several joints, the two most important being:

  1. Glenohumeral (GH) joint – the ball-and-socket joint between the humerus (upper arm bone) and the scapula (shoulder blade).
  2. Acromioclavicular (AC) joint – a smaller joint where the acromion (a bony projection of the scapula) meets the clavicle (collarbone).

The AC joint helps maintain shoulder positioning and allows for complex overhead and rotational movements. It is stabilized by:

  • AC ligaments – provide horizontal stability.
  • Coracoclavicular (CC) ligaments – provide vertical stability.

The ends of the bones in the AC joint are covered in articular cartilage, which cushions the joint and allows for smooth, pain-free motion.

Osteoarthritis (OA) is a condition where the protective cartilage covering the joint surfaces gradually breaks down. In the AC joint, this results in:

  • Joint space narrowing
  • Bone spur formation (osteophytes)
  • Thickening of the joint capsule
  • Joint inflammation

Over time, these changes lead to pain, stiffness, and loss of mobility in the shoulder. While some degree of cartilage wear is common with aging, not all patients develop painful symptoms.

The most common causes of AC joint osteoarthritis include:

Degenerative (Primary) Osteoarthritis

  • Due to natural aging and wear-and-tear over time.
  • Most common in individuals over age 50.

Post-Traumatic Osteoarthritis

  • Following an AC joint injury, such as a separation or fracture.
  • May occur even years after the injury.

Repetitive Use or Overload

  • Seen in athletes and manual laborers who perform repeated overhead motions (e.g., weightlifters, swimmers, painters, carpenters).
  • Lifting heavy weights places significant stress on the AC joint.

Risk Factors

  • Prior shoulder trauma
  • Repetitive overhead activity
  • Participation in contact or overhead sports
  • Heavy lifting
  • Genetics or family history of arthritis

Symptoms of AC joint osteoarthritis may develop gradually and include:

  • Pain on top of the shoulder, often localized to a small spot
  • Pain with overhead or cross-body movements
    • Example: reaching across the chest, lifting arms overhead, bench pressing
  • Tenderness or swelling over the AC joint
  • Painful clicking or popping with shoulder movement
  • Visible bump or enlargement of the joint from bone spurs
  • Night pain, especially when lying on the affected shoulder
  • In advanced cases, loss of motion and difficulty with daily activities

Pain is typically worse with activities that compress the joint, such as push-ups, planks, bench presses, or carrying objects across the chest.

History and Physical Exam

  • Evaluation of symptoms, activity level, and any history of trauma.
  • Palpation of the AC joint often reproduces pain.
  • Cross-body adduction test (bringing the arm across the chest) is a common physical exam maneuver that may elicit pain in AC joint arthritis.

Imaging

  • X-rays are the primary diagnostic tool.
    • Show joint space narrowing, bone spurs, sclerosis (hardening), or cysts.
  • MRI or ultrasound may be used to:
    • Rule out other shoulder conditions (e.g., rotator cuff tears)
    • Assess soft tissue inflammation, joint fluid or bone bruising.

The majority of patients with AC joint osteoarthritis can manage symptoms without surgery.

Activity Modification

Avoid or limit movements that stress the AC joint:

  • Overhead lifting
  • Cross-body motions
  • Heavy weightlifting (e.g., bench pressing, planks)

Physical Therapy

Strengthening and stretching exercises to:

  • Improve shoulder mechanics
  • Enhance scapular stability
  • Reduce compensatory strain

Medications

  • Over-the-counter NSAIDs (ibuprofen, naproxen) help reduce pain and inflammation.
  • Topical anti-inflammatory creams may also be useful.

Ice or Heat Therapy

  • Ice can reduce inflammation and pain after activity.
  • Heat may help loosen stiff muscles before exercise.

Corticosteroid Injections

  • An injection of corticosteroids directly into the AC joint can provide temporary relief (weeks to months to years)
  • Useful for flare-ups or to confirm that the AC joint is the pain source.
  • Injections may be repeated sparingly but repeat injections can be done depending on how effective past injections have been

Surgery is recommended for patients who:

  • Have persistent symptoms despite several months of conservative treatment
  • Experience significant functional limitations or night pain
  • Have confirmed AC joint arthritis as the primary source of pain

Distal Clavicle Resection (Mumford Procedure)

  • The most common surgical procedure for AC joint osteoarthritis.
  • Involves removal of 5–10 mm of the outer (distal) end of the clavicle.
  • Eliminates bone-on-bone contact and allows space for pain-free shoulder motion..
  • Often performed arthroscopically: Minimally invasive, performed with a camera and small tools through tiny incisions.
  • Often combined with other procedures (e.g., rotator cuff repair if needed)

Recovery After Surgery

  • Outpatient surgery (same-day discharge)
  • Sling used for comfort for 1-3 days
  • Early motion encouraged
  • Physical therapy begins within 1 week
  • Return to normal activity in 4–8 weeks
  • Full recovery expected in 2–3 months

Nonoperative Outcomes

  • Many patients improve and return to all activities with therapy, activity modification, and medication.
  • Symptoms may fluctuate but can often be controlled long-term without surgery.
  • Some patients may continue to have mild discomfort or restricted activity.

Surgical Outcomes

  • Distal clavicle excision has high success rates (80–90%+)
  • Most patients experience:
    • Significant pain relief
    • Improved shoulder motion
    • Return to sports or work
  • Risks are low but may include:
    • Infection
    • Shoulder stiffness
    • Persistent pain if arthritis is not the only problem
    • Incomplete resection (rare, may require revision)

Arthroscopic surgery generally has a quicker recovery and less postoperative pain compared to open procedures.

See a healthcare provider if you experience:

  • Shoulder pain at the top of the shoulder that limits daily activity
  • Pain that worsens with overhead or cross-body movement
  • Swelling, clicking, or joint enlargement
  • Persistent symptoms despite home care and rest
  • Difficulty lifting or using the shoulder in work or sports

AC joint osteoarthritis is a common source of shoulder pain in adults, particularly those with a history of trauma or repetitive overhead activity. Most cases respond well to nonoperative treatments such as physical therapy, medications, and lifestyle changes. In patients with persistent symptoms, a surgical procedure called distal clavicle excision can provide reliable relief. With early recognition and appropriate management, most individuals return to their normal activities with good shoulder function.

At a Glance

Dr. Hasani Swindell

  • Fellowship-Trained Sports Medicine Specialist
  • Board-Certified Orthopedic Surgeon
  • Summa Cum Laude Graduate from the University of Pittsburgh
  • Medical Degree from Columbia University
  • Learn more
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