There are two peroneal tendons behind the outer bone of the ankle. They run down behind the ankle and go into the foot. They turn the foot outwards and stabilize the ankle dynamically.
Most sports have elements of running and lateral movement. Sports such as running on uneven surfaces, football can be highly demanding on the ankle. Peroneal tendons balance the ankle and foot against the inward movement, which can be due to an over pull of a stronger muscle on the inner side of foot or deficiency of ligaments on the outer side of foot (due to ankle sprain). Maximal exertion occurs with side-to-side movement and jumping.
Trauma to the lateral ankle distorts the proprioceptive sense (ability to balance) and stretches the connective tissues. The peroneus muscles are often stretched and injured from traction when the foot inverts. Ankle instability ensues and continues until the peroneal muscles recover, and proprioception returns. If the peroneal tendons do not recover, symptoms of instability may not resolve without further intervention.
Repeated inward turning injury to the ankle will overstretch the peroneal tendons leading to tears and degeneration n them. Similarly if a violent or a high velocity force turns the ankle inwards, these tendons can be injured (torn/dislocated) in first instance itself. Long term neglect of ankle instability makes them over work to restore stability dynamically and this can cause inflammation in and around them (swelling around the tendon within their protective coating).
Acute injury will present like a severe ankle sprain with pain, swelling around the ankle, especially on outer aspect. A dislocated tendon, which has popped out of its groove may be seen / felt over the outer bone of the ankle. Long term neglected injuries will present with ankle instability along with swelling and pain along the tendon, signifying tears in the tendon. These ankles do not respond to physiotherapy alone and their instability persists. It is important to get this ankle examined by an orthopaedic surgeon to start appropriate treatment and prevent complete rupture.
Detailed clinical examination by a specialist gives adequate clues to the diagnosis. This can be confirmed by a ultrasound examination, which can check it dynamically to confirm dislocation or a MRI scan.
Acute injuries need to be rested in an ankle immobilizing boot. Foot elevation and NSAIDs help in getting the swelling down. This helps the tendon and its protective sheath heal in a stable position, but in most active individuals, especially keen athletes, this is unsatisfactory. If individuals continue to experience pain, swelling & instability, they may require surgery to repair the torn tendon and stabilize in its groove. This can be visualized using a keyhole surgery (Tendoscopy of peroneal tendons) and appropriate further management is carried out.