cases, extremity Week 139: Case 2 April 26, 2023 pathadmin 1. Presented by Edward McCarthy, M.D. and prepared by Anil Parwani, M.D.,Ph.D.A man in his 40s had a painful knee for three months. An arthroscopic exam demonstrated a deep, brown-pigmented fronds of synovial membrane. A biopsy was performed.Pigmented villonodular synovitisRheumatoid snynovitisHemosiderotic synovitis 1. Presented by Edward McCarthy, M.D. and prepared by Anil Parwani, M.D.,Ph.D.A man in his 40s had a painful knee for three months. An arthroscopic exam demonstrated a deep, brown-pigmented fronds of synovial membrane. A biopsy was performed.