A new evaluation of gross pathologic changes and concepts of rheumatoid articular cartilage degeneration.

Fifty-one knees in 32 ambulatory patients with rheumatoid arthritis were examined arthroscopically, enabling direct observation of the pattern of gross degeneration at the joint line and synovial chondral junction. Four distinct stages of pannus ingrowth and meniscal degeneration were observed, which correlated with the extent of articular destruction. Significant direct pannus invasion of articular cartilage was not observed in any stage in the ambulatory mobile rheumatoid knee. Stage I is comprised of synovial hypertrophy. Stage II shows invasive pannus affecting meniscal surfaces. Stage III exhibits meniscal tearing and production of abrasive debris. Stage IV is end-stage loss of meniscus and denudation of articular surfaces. Articular cartilage destruction was not observed in patients without visible meniscal degeneration or pannus ingrowth but was observed in knees without roentgenographic erosion or joint space narrowing. A new evaluation of articular degeneration in the ambulatory mobile rheumatoid knee is based on mechanical destruction by torn menisci and free debris observed by arthroscopy.