The possibility of pigmented villonodular synovitis (PVNS) is considered. Differential diagnoses include 'cyclops lesion', and intra-articular chronic hematoma. However, in view of the lack of trauma-related history, and intact ligaments, PVNS merits primary consideration.

The patient is not ready for any intervention and sustaining similar symptoms since the study done previously. Pathological diagnosis is unavailable.

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).