Radiological features are in favour of pigmented villonodular synovitis of the ankle joint and giant cell tumour of the flexor hallucis longus tendon sheath.

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