200 Section - The “Saddlebag” Knee: Rice Body Synovitis as a Cause of Persistent Effusions in Rheumatoid Arthritis

Rheumatoid arthritis–associated rice body effusion with superimposed tricompartmental osteoarthritis

Case Description:

A 57-year-old man with rheumatoid arthritis (RA) presented with pain and swelling, described by the patient as “saddlebags” on the knees. He denied trauma. A prednisone course improved systemic symptoms, but knee pain persisted. Examination showed a nonantalgic gait, preserved strength and range of motion, and a moderate left knee effusion with bilateral joint-line tenderness. Radiographs demonstrated moderate tricompartmental osteoarthritis with bilateral effusions. Left knee aspiration yielded clear yellow fluid containing dense visible clumps consistent with rice bodies, limiting aspiration; cultures and crystal analysis were negative. Quantiferon-TB testing was negative despite a history of latent tuberculosis. Laboratory studies revealed leukocytosis. Bilateral intra-articular corticosteroid injections were performed. The course was complicated by failure of multiple disease-modifying anti-rheumatic drugs. After initiation of adalimumab and low-dose prednisone, disease activity improved substantially, with acceptable knee pain despite residual effusions attributed to remnant rice bodies.

Discussions:

Rice body synovitis is a rare manifestation of chronic inflammatory arthritis and is frequently associated with rheumatoid arthritis, osteoarthritis, or tuberculous arthritis. Rice bodies are free synovial corpuscles encountered microscopically in up to 35% of RA synovial fluid samples; however, larger accumulations causing palpable findings are uncommon. In this patient, palpable anteromedial knee “saddlebags,” while not standard terminology, were felt to represent accumulations of intra-articular rice bodies, explaining persistent effusions and mechanical symptoms despite improvement in systemic disease. In the knee, rice bodies may contribute to local compression and mechanical interference with joint function. While surgical intervention is definitive for residual rice bodies, intra-articular injections were an important adjunct when localized inflammatory reservoirs persisted despite systemic control and coexisting osteoarthritis.

Conclusions:

Rice body synovitis should be considered in patients with RA and persistent knee effusions despite systemic disease control. Recognizing rice bodies aids diagnostic clarity and informs localized and systemic management.