External synovial fistula of the knee joint and its treatment with free radial artery fasciocutaneous flap

External synovial fistula of the knee joint is a rare entity. A case is reported in which the fistula presented 12 years after the original injury. The nature of injury and previous surgery precluded the use of a local flap. Treatment was successful using a foe fasciocutaneous flap. Exposure of vital structures and metal work are the common indications for flap cover in the lower extremity. However synovial fistula is another instance where flap cover may be required. This case report emphasises the possibility of delayed presentation of a synovial fistula and the need for prompt closure, since it can be a path for retrograde infection.