Painful knee locking caused by gouty tophi successfully treated with allopurinol.

BACKGROUND: A 67-year-old man presented to a rheumatology clinic with a 1-week history of severe pain and swelling of his right knee. He had been receiving allopurinol for about 5 months for the treatment of chronic gouty arthropathy of more than 30 years' duration. On examination, his right knee was warm and swollen. The aspirated fluid contained intracellular and extracellular monosodium urate crystals, but Gram staining and culture were negative. The affected knee was injected with triamcinolone, but the patient continued to experience severe pain and complained of locking of the knee 3 weeks after the onset of his initial symptoms. Physical examination at this time showed no sign of inflammation, but the knee had a very limited range of motion. INVESTIGATIONS: Physical examination; routine laboratory investigations, including CBC, complete metabolic panel, measurement of serum uric acid levels, and synovial fluid analysis; radiological investigations, including radiography of the right knee and CT of the right knee with intra-articular contrast. DIAGNOSIS: CT showed no internal derangement, but revealed extensive intra-articular and extra-articular amorphous soft tissue calcifications, compatible with gouty tophi. MANAGEMENT: The patient declined an arthroscopic procedure to remove the gouty tophi. Treatment consisted of continuous allopurinol therapy and narcotics for symptomatic pain relief. Over the next 12 months, the patient's serum uric acid levels, and presumably his total-body urate pool, were substantially reduced. The knee unlocked and the pain subsided. Follow-up CT about 3 years after the initial examination showed complete resolution of the calcified intra-articular and extra-articular tophi.