AC Joint Arthritis & Distal Clavicle Osteolysis

Understanding AC Joint Arthritis & Distal Clavicle Osteolysis

The acromioclavicular (AC) joint, at the top of the shoulder where the collarbone meets the shoulder blade, can wear out with age, after a prior separation, or from heavy lifting. Arthritis of the AC joint causes pain right at the top of the shoulder, especially when reaching across the body, lifting overhead or doing bench presses and dips.

Distal clavicle osteolysis, sometimes called "weightlifter's shoulder," is a related condition in which repeated stress causes the end of the collarbone to soften and break down, typically in younger people who lift weights.

Wear of the AC joint on MRI is extremely common: one study found it in 75% of people over 40 and in everyone over 70, so imaging alone cannot show whether the AC joint is the source of pain ^[1]. The diagnosis is made from the exam, and a numbing injection into the joint can confirm it. Most patients improve with activity changes and injections. When pain persists, arthroscopic distal clavicle excision removes a small amount of the end of the collarbone; in a prospective series, pain scores dropped substantially and most patients returned to sport within about two months and to work within about three ^{[2, 3]}.

Causes & Risk Factors

• Age-related wear (osteoarthritis)
• A previous shoulder separation (AC joint injury)
• Repetitive heavy lifting, especially bench press and dips (distal clavicle osteolysis)
• Inflammatory arthritis

Symptoms

Common signs and symptoms of AC Joint Arthritis include:

• Pain at the very top of the shoulder
• Pain reaching across the body or behind the back
• Pain with bench press, dips or overhead lifting
• Swelling or a bump over the AC joint
• Clicking or grinding at the top of the shoulder

Treatment Options

Treatment for AC Joint Arthritis depends on the severity of your condition and may include:

• Activity modification, such as changing lifting technique
• Anti-inflammatory medication
• Corticosteroid injection into the AC joint
• Physical therapy
• Arthroscopic distal clavicle excision

References

1. Rajagopalan D, Abdelaziz A, Ring D, et al. MRI findings of acromioclavicular joint osteoarthritis are the norm after age 40. Orthop Traumatol Surg Res. 2023;109(4):103526. doi.org/10.1016/j.otsr.2022.103526
2. Flatow EL, Duralde XA, Nicholson GP, et al. Arthroscopic resection of the distal clavicle with a superior approach. J Shoulder Elbow Surg. 1995;4(1 Pt 1):41-50. doi.org/10.1016/s1058-2746(10)80007-2
3. Leon JV, Hermans D, Venkatesha V, et al. Patient outcomes following arthroscopic distal clavicle excision: a prospective case series. JSES Int. 2023;7(6):2400-2405. doi.org/10.1016/j.jseint.2023.07.014