The 2 bones in your lower leg (the tibia and fibula) are joined by an interosseous membrane or connective tissue. At the distal end of these bones close to the ankle joint this forms a fibrous joint called a syndesmosis. Trauma to the ankle can sometimes damage this area which is otherwise called a ‘high ankle sprain’. It is an injury that is commonly missed and can therefore delay recovery of what is otherwise considered to be a standard ankle sprain.