Case Report: Arthroscopic management of a giant Baker cyst containing numerous rice body-like loose bodies in a patient with rheumatoid arthritis.

BACKGROUND

Giant Baker cysts containing numerous rice body-like loose bodies are uncommon and can resemble vascular, infectious, or neoplastic lesions.

CASE PRESENTATION: A 30-year-old woman with a 4-year history of rheumatoid arthritis presented with 1 year of progressive left knee pain, restricted flexion, and a 15 × 8 cm nonpulsatile mass extending from the popliteal fossa into the proximal calf. Magnetic resonance imaging showed a well-defined cystic lesion containing numerous nonmineralized intraluminal nodules. Arthroscopy demonstrated diffuse hypertrophic synovitis and multiple smooth ivory-white loose bodies. Synovectomy, loose-body removal, cyst decompression, and debridement of the cyst-joint communication were performed. Histology of the cyst wall and synovium showed chronic inflammation and fibrosis, without malignancy, cartilaginous metaplasia, granulomatous inflammation, or caseous necrosis. No isolated loose body had been separately embedded or sectioned. Results of interferon-gamma release assay, Ziehl-Neelsen staining, mycobacterial culture, and molecular testing were unavailable for retrospective review. At 12 months, the swelling had resolved, flexion improved from 110°to 130°, and ultrasonography showed no clinically significant recurrence of the popliteal cyst.

CONCLUSION

Arthroscopy may provide tissue diagnosis and allow treatment of associated synovitis and the cyst-joint communication in selected patients. Detailed documentation of operative access and microbiological assessment is important for interpretation and reproducibility.