Crystal deposition in the knee and great toe joints of asymptomatic gout patients.

Crystal deposition in asymptomatic knee and first metatarsophalangeal (MTP) joints has been studied in 31 patients with previously proven gout. All had had clinical gout in their MTP joints but their knee joints had never been the site of acute gout. Knee arthroscopy was performed permitting synovial membrane inspection, photography and biopsy. Crystalline material was seen in 9 knees (28%) and confirmed histologically as monosodium urate (MSU) in 4 (12.5%). Synovial fluid analysis on 26 samples using a polarizing light microscope demonstrated MSU crystals in 4 (12.5%) and calcium pyrophosphate dihydrate (CPPD) in 2 (6%). Fluid aspirated from 27 of the metatarsophalangeal joints revealed MSU crystals in 14 (52%) and no CPPD crystals.