Chronic Peroneal Tendon Subluxation
Chronic Peroneal Tendon Dislocation
Edited by Matthew Buchanan, MD
The peroneal tendons are two rope-like structures located behind the bone (fibula) on the back outside part of the ankle (Figure 1). A subluxing peroneal tendon creates pain, as one of the rope-like peroneal tendons pops in and out (subluxes) of its position behind the ankle. This condition often occurs chronically, but acute peroneal tendon subluxation may also occur following a precipitating injury. Treatment of chronic peroneal tendon subluxation involves avoiding precipitating activities, and possibly taping the ankle to minimize tendon subluxation. Operative treatment is reserved for chronic peroneal subluxation that cannot be addressed non-operatively, and that consists of repairing the torn fibrous tissue (retinaculum) that would normally keep the tendon in place.
Figure 1: Peroneal Tendons and SPR
Patients with chronic peroneal tendon subluxation will complain of pain, along with a sensation of a moving or snapping tendon on the outside of their ankle. They will note that when their foot is in certain positions, they will feel a sensation of one of the peroneal tendons (peroneus brevis) moving behind their ankle, and this will often be associated with a sharp pain. Subluxation of the peroneal tendons will usually occur when the heel is pointed to the outside, or perhaps when the foot is loaded and the patient is rotating over top of it. In some cases, the peroneal tendon can be flipped in an out of its groove behind the fibula at the will of the patient — essentially the tendon is rolled back and forth over the bone (fibula) on the outside of the ankle. Patients will often give a history of a previous injury leading to displacement of the tendons on the back part of the ankle (acute peroneal tendon subluxation), although some chronic peroneal tendon subluxations can occur spontaneously if the restraining tissues get gradually stretched out. There is normally a strong fibrous structure called the superior peroneal retinaculum (SPR) that keeps the peroneal tendons in place behind the bone on the outside of the ankle (fibula). In order for the peroneal tendon to flip (sublux) outside of its normal positions, this structure (the SPR) must have been torn or become stretched out.
Patients with chronic peroneal tendon subluxation will often have tenderness located behind the bone on the outside of the ankle. In addition, with the back part of the foot pointed to the outside (everted), the tendons will often be able to move out of position and this demonstration clinically of the subluxation of the tendons confirms the diagnosis. The pain is usually quite localized. It’s not uncommon for patients to have a higher arched foot, as this foot shape predisposes to increased tension through the peroneal tendons.
Your doctor will order plain (regular) x-rays of the hindfoot. These will often be normal. Occasionally, a small rim of bone associated with the back part (posterior) of the fibula will be noted that is consistent with a previous old avulsion injury, whereby the superior peroneal retinaculum pulls off a small fragment of bone (fibula).
An MRI will often show a disruption of the superior peroneal retinaculum (SPR). In addition, an MRI or a CT scan can be used to assess the shape of the back part of the fibula. The reason this is important is that normally this shape should be concave, essentially creating a cavity in which the tendons run. In some patients, the shape of the bone is flat or even convex, and this will predispose to subluxation of the peroneal tendon.
Ultrasound may be used to visualize what the subluxing tendon is doing dynamically. It can help identify the shape of the fibula, and assess the extent of damage to the peroneal retinaculum.
Chronic peroneal tendon subluxation can often be successfully treated non-operatively. If the subluxation events occur relatively infrequently, and only with certain sporting activities, then taping or immobilizing the ankle with an ankle lacer can be helpful to minimize the chance of a recurrent subluxation episode.
Surgical treatment is indicated if the subluxation is regular and significantly impacts the patient’s lifestyle. They type of surgery is dictated by the extent of injury to the involved structures (ex. tearing or stretching out of the superficial peroneal retinaculum) that is identified on clinical exam and imaging studies. The goal of surgery is to keep the tendons contained within the canal behind the fibula. Part of the surgical reconstruction involves repairing the superior peroneal retinaculum back to bone, so that there is no longer a sleeve of retinaculum that the tendons can roll under. In addition, in some patients, a bony procedure is required in order to deepen the back part of the fibula to create an appropriate cavity for the tendons to run in.
Recovery from surgery requires a moderately long period, usually in the order of 2-6 weeks of immobilization, in order to allow the retinaculum and any bony procedures to heal. This is followed by four to six weeks of fairly graduated and intensive rehabilitation. It is often six months or more before the patient has reached a lot of their improvement following the surgery.
Complications that are specific to a repair of the superior peroneal retinaculum include:
- Recurrence of the peroneal tendon subluxation. The surgical repair can stretch out or be reinjured, leading to recurrence of the peroneal tendon subluxation.
- Nerve injury. The sural nerve may be injured. This nerve supplies the sensation to the outside of the foot. An injury to this nerve can result in numbness over the outside of the foot or a burning sensation radiating towards the outside of the foot.
Edited June 30, 2019