PVNS is a chronic inflammatory lesion affecting the synovial membranes resulting in synovial hypertrophy, forming villous and nodular projections and causing pressure erosion of the adjacent bones. Although the appearance is radiologically classic for PVNS yet other differential diagnosis include siderotic synovitis, synovial osteochondromatosis and rheumatoid arthritis.

Editor's note: Per the 2020 WHO Soft Tissue and Bone Tumors Classification (5th ed.), the recommended terminology is tenosynovial giant cell tumor with pigmented villonodular synovitis no longer recommended (although remains in common use).