Urate Crystals Discovered Lurking in Osteoarthritic Knees

October 16, 2013

ACR2013: Urate crystals turned up in dual-energy CT and pathology studies of OA patients never diagnosed with gout who came to the Mayo Clinic for knee replacement, raising intriguing questions.

Could uric acid in synovial fluid contribute to the progression of osteoarthritis (OA)? A group of Mayo Clinic researchers found this more than a merely interesting suggestio.  They decided to take a look, with results that beg for further research.

In a pilot study to be reported as a poster presentation at the American College of Rheumatology annual meeting, Tim Bongartz MD and his coworkers assessed samples of cartilage, menisci, and synovium from five patients who had undergone total knee replacement, none of whom had a previous diagnosis of gout. The selection of samples was guided by preoperative dual-energy CT scans that identified probable sites of urate crystal deposition.

Microscopic studies by a musculoskeletal pathologist discovered urate crystals in cartilage and menisci from four of the five patients, and in synovial samples from two. Serum uric acid levels in these patients ranged from 5.0 to 6.4 mg/dL, with a mean of 5.7.

How widespread is this phenomenon in the general population of patients with severe OA but no evidence of gout? And does the presence of the crystals actually accelerate cartilage damage? The abstract asks these questions but cannot, of course, yet offer an answer.