Distal Clavicular Osteolysis. There is resorption of the distal clavicle and small cysts in the distal clavicle 
in this young weight lifter with pain in this region for several months (white arrows).
en.wikipedia.org/wiki/Bone_resorption Bone resorption  is the process by which osteoclasts break down bone and release the  minerals, resulting in a transfer of calcium from bone fluid to the  blood 
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General Considerations
- Sequela of trauma       from contact sports, falls and motor vehicle accidents
 
- Incidence increased       with weight lifting/training                 
- Other sports  include football, swimming
 
 
- More often seen in       males
 
- Unilateral
 
- Atraumatic causes are       more common than traumatic
 
- Continued stress on       the joint may play a role in its development
 
Clinical Findings
- Dull aching pain over       AC joint
 
Imaging Findings
- Diagnosis can usually       be made with conventional radiography and history
 
- Resorption of distal       clavicle
 
- Osteopenia of distal       clavicle
 
- Periarticular       swelling
 
- Periarticular       cyst-like erosions
 
- Periostitis of       clavicle
 
- Bone scan will be positive       in distal clavicle
 
Differential Diagnosis
- Hyperparathyroidism
 
- Rheumatoid arthritis
 
- Scleroderma
 
Treatment
- Non-steroidal       anti-inflammatory drugs
 
- Steroid injections
 
- Distal clavicle       resection
 
Complications
- Higher incidence in       patients with a prior AC separation
 
- Permanently widened       AC joint and persistent pain
 
Prognosis
- Self-limiting about       1-2 years following modification of activity which caused disease
 
- Osteolysis may       reverse