Distal clavicle osteolysis, also known as weight lifter's shoulder, is a shoulder injury affecting the acromioclavicular (AC) joint. It is most commonly associated with contact sports in which high stresses are placed on the clavicle, or collar bone. The exact cause of distal clavicle osteolysis, however, is not known. Symptoms can appear slowly and include a dull aching over the AC joint, reduced mobility, stiffness and swelling in the shoulder, and reduced strength. Symptoms can worsen with continued activity.

Osteolysis refers to the loss of minerals, such as calcium, in the bone, causing a softening or dissolution of the bone. In distal clavicle osteolysis, the end, or distal part, of the clavicle begins to slowly break down and dissolve. This can be caused by a single injury to the AC joint, smaller repetitive injuries, repetitive stresses on the AC joint such as in weight lifting, or a pre-existing disease that might affect the mineralization of the bone structure, such as rheumatoid arthritis.

Changes in the bone structure happen over time but can usually be diagnosed with the aid of x-rays and a patient history. Treatment for distal clavicle osteolysis depends on the amount of bone loss. In most cases, avoidance of symptomatic activity or modification of activities, in conjunction with anti-inflammatory medicines and ice can allow the clavicle to remineralize. This process can take up to two years to fully resolve. Symptoms often return if previous activities are resumed.

Surgery might be required if the bone does not remineralize, or if a patient is unable or unwilling to limit his or her activity. The most common form of surgery for distal clavicle osteolysis is a distal clavicle resection, or arthroscopic distal clavicle resection, in which the affected portion of the bone is removed. Post-operative healing times vary, but limited range of motion can return within one to two weeks following surgery.

Distal clavicle osteolysis can be prevented in some cases. Experts recommend cessation of all exacerbating activities as soon as AC joint pain presents itself. For those playing contact sports, extra padding is recommended. Weight lifters can avoid injury by taking a narrower grip on the bar and avoid the locking or overextension of the elbows.

The first recorded injury of distal clavicle osteolysis was in 1936. In this case, an air hammer operator presented with a sore shoulder and no outlying trauma. Occurrences of these injuries increased as both awareness and the popularity of competitive sports increased.