INTRODUCTION: Synovial haemangioma is a rare intra-articular benign tumour, which may arise from any synovium-lined surface, but particularly in the knee joint. Synovial haemangioma originating from the anterior cruciate ligament has not been reported previously. CASE PRESENTATION: A 34-year-old man presented with a history of intermittent knee pain, locking and swelling. CONCLUSION: Knee intra-articular haemangioma, a very rare benign tumour, is often misdiagnosed. Magnetic resonance imaging is effective in detecting this lesion and should be performed in cases of persistent knee swelling and pain.