An 82-year-old man with bilateral knee osteoarthritis underwent consecutive total knee arthroplasty 5 months apart. During both procedures, he was noted to have black subchondral bone with otherwise normal architecture and normal-coloured cancellous bone. At the time of surgery, bone specimens sent for pathology testing were histologically normal. The patient had been treated with minocycline for rosacea for 7 months before the first procedure. Minocycline is an uncommon cause of skeletal pigmentation and is not known to affect bone quality.1 Discolouration may also be owing to ochronosis, metal deposits, sequestrum and metastatic disease.2
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