In the present understanding of joint pathology, the exact pathogenic role of hydroxyapatite crystals, both periarticular and intraarticular, is not yet completely clear. An association between rapidly destructive osteoarthritis (OA) and hydroxyapatite or basic calcium crystals was confirmed. This is a case report of a 78-year old female patient presenting with a five-month history of shoulder pain with swelling of both AC joints. Imaging showed a large bursitis starting in the AC joints of both shoulders. Synovial fluid analysis showed many hydroxyapatite crystals and no calcium pyrophosphate or sodium urate crystals, which confirmed the diagnosis of crystal-induced periarthropathy and AC arthritis. These periarticular radiographic and synovial fluid findings are a frequent and known manifestation of hydroxyapatite crystal deposition disease, similar to the intra-articular destructive "Milwaukee shoulder syndrome". Surgical intervention was the only therapeutic option to reduce the patient's shoulder pain.