Pseudo-deep vein thrombosis in rheumatoid arthritis.

Acute synovial rupture is encountered in several types of arthritis but is most common in rheumatoid arthritis. Chronic synovitis producing tense effusion in the knee may result in a posterior capsular tear. The clinical picture closely mimics acute thrombophlebitis, and failure to recognize the true cause often results in inappropriate anticoagulant therapy, with further deterioration of the leg. Ultrasonography is a useful screening procedure. When operation is undertaken, the posterior capsular defect must be repaired.