The peroneal tendons are two tendons that run along the outer side of the foot and ankle. One of the tendons connects to the outside of the midfoot, and the other runs under the foot and connects to the midfoot. Both tendons work to evert and turn out the foot. They can also help to plantar flex (point your toes) the ankle and help stabilize the ankles during running and side to side activities. The tendons run in a bony groove on the posterior portion of the fibula, and a strong fibrous band called the peroneal retinaculum helps to hold them in place.
Injuries to the peroneal tendons can occur in several ways. Most often, peroneal tendinitis occurs in runners. Tendonitis is inflammation of the tendon and the tissue surrounding the tendon. Tendonosis can also occur, which is thickening and swelling of the tendon. These changes in the tendon are usually a result of overuse and “microdamage” that accumulates over time. Occasionally the tendon itself can rupture or split. In other cases, the peroneal retinaculum that keeps the tendons in the peroneal groove ruptures, and the tendons “sublux” or slip out of the groove with certain movements.
What are the Signs and Symptoms of Peroneal Tendonitis/Tendonosis?
The most common symptom is pain in the lateral (outside) and posterior (back) portion of the ankle with repetitive activities. It is commonly seen in athletes who have recently increased their activities, such as those training for a marathon or athletes starting a new portion of their season. This is especially true in sports which require repetitive ankle motion (most running sports). Athletes with hindfoot varus (heel turns in) and/or high arches are more susceptible to peroneal tendonitis/tendinosis because the tendon has to work harder during ankle stabilizing activities. Recent research has also indicated that athletes with weak hip and core musculature are more susceptible to these injuries.
How is Peroneal Tendonitis/Tendinosis Diagnosed?
The most important part of diagnosis is the history and physical examination. Patients with this condition have often started a new training regimen or have increased their mileage. On exam, they usually have pain that is localized to the posterolateral portion of their ankle and tracks along the normal course of the peroneal tendons. There can be pain with passive inversion or resisted eversion of the foot. If there has been disruption of the peroneal retinaculum (usually from a specific injury), the tendons can be felt to sublux, or slide out of, the peroneal groove on the back of the fibula during ankle circumduction maneuvers. It can be difficult to distinguish between peroneal injury and an injury to the fibular (bone on the outside of the ankle) or the 5th metatarsal (bone on the outside of the foot). The sural nerve also runs in this general area and can sometimes be associated with pain in this region. X-rays usually don’t show any signs of injury, but will sometimes show a bony “fleck” if there is an avulsion of the peroneal retinaculum. They can also show a fracture to the bones in that area. MRI is sometimes used to assess the tendons for a split, to look for a tear in the retinaculum, or to assess for a stress fracture.
How are Peroneal Injuries Treated?
Most peroneal tendon injuries are treated nonoperatively. The first step is to temporarily reduce the repetitive activities that stress the peroneal tendon. Most patients will need to be placed into a Cam walker boot or something similar to immobilize the ankle for a period of time. After the inflammation has settled down, rehabilitation should be started. This will consist of ankle specific exercises to stretch and strengthen the peroneal tendons, as well as exercises targeted at more proximal muscle groups such as the hip external rotators and the hip abductors. Proper shoe wear should be fitted, and accommodations or orthotics may be needed for patients with hind foot varus. Steroid shots are usually not recommended in this area except in cases of extreme inflammation that is resistant to other forms of treatment. PRP inections have been utilized with some success, although the evidence is still early and PRP is somewhat unproven for this condition. In cases of peroneal retinacular tear or tears of the peroneal tendons themselves, surgical treatment is sometimes need to repair the retinaculum and/or tendon. Occasionally, the bone on the posterior portion of the fibula is deepened to provide a better groove for the tendons to fit in.
How are Peroneal Tendon Injuries Avoided?
The best way to treat peroneal tendonosis is to avoid it. This can be done most effectively by adequate training of the proximal lower extremity muscle groups. Poor lumbopelvic trunk and hip control can alter gait mechanics in a way that leads to lower extremity injury such as that seen in peroneal tendonsis/tendonitis. Proper shoewear is a must, especially if you have high arches or a cavovarus foot. And finally, make sure you gradually lead into significant increases in training volume.
Further information for runners: https://runnersconnect.net/peroneal-tendinitis-tendonitis/