Peroneal Tendonitis

The peroneal tendons run on the outside of the ankle just behind the bone called the fibula. The Peroneal tendons connect the peroneus longus and brevis muscle to bone and allow them to exert their force across the joints that separate bones. Tendinitis implies that there is inflammation in the tendon. This usually occurs in the setting of overuse, meaning the cause is usually a repetitive activity that irritates the tendon over long periods of time.

Peroneal Tendonitis Symptoms

Patients will usually present with pain around the back and outside of the ankle. There is usually no history of a specific injury although a history of a sprain may be present. Swelling is evident in most cases. The pain is usually relieved by rest, ice and NSAIDS. Activity and overuse usually makes the pain worse.

Causes of Peroneal Tendonitis

As discussed above, overuse such as improper training or rapid increases in training and improper shoewear can lead to peroneal tendonitis. Also, patients who have a high arch (varus) posture may be more susceptible. This is because in those patients, the heel is slightly turned inwards which requires that the peroneal tendons work harder. Their main job is to evert or turn the ankle to the outside, which fights against the inwards (varus) heel position. The harder the tendons work, the more likely they are to develop tendonitis.

Peroneal Tendonitis Anatomy

​There are two peroneal tendons that run along the outside of the ankle (Figures 1 and 2). The first is called the peroneus brevis. The term "brevis" implies short. It is called this because it has a shorter muscle and starts lower in the leg. It then runs down around the back of the ankle and on the outside of the leg. It attaches to the fifth metatarsal base on the outside of the foot. The peroneus longus as implied has a longer course. It starts higher on the leg and runs all the way underneath the foot to insert or connect on the first metatarsal on the underside. Both tendons work at everting or turning the ankle to the outside.

Peroneal Tendonitis Symptoms

There is pain to palpation right on the peroneal tendons. It is important to distinguish this from pain over the fibula, which might indicate a different problem (i.e. stress reaction of the bone). Pain in the peroneal occurs slightly further behind. There is also pain with turning the foot to the inside towards the middle of the body. There may also be weakness in trying to bring the ankle to the outside.

The workup can also include using radiology. X-rays will typically be normal. Ultrasound is a very effective and relatively inexpensive way to assess the tendons and can show an abnormal appearance or tear which sometimes occurs. An MRI is also equally important and can also show a tear.

Peroneal Tendonitis Treatment

The vast majority of peroneal tendonitis will heal without surgery. This is because it is an overuse injury and can heal with rest. If there is significant pain, a CAM Walker boot for several weeks is a good idea. If there really is no tenderness with walking, an ankle brace might be the next best step. Patients should limit how much they are exercising to allow for resolution of the symptoms. This usually takes several weeks to several months. Resumption of training can then occur, but must occur very slowly and be based on pain. For those patients who have mechanical alignment issues an orthotic that tilts the ankle to the opposite side may well help to offload the tendons. It is important to talk to your doctor about changing your training. This includes using new shoes for running or also cross-training, which means alternating activities each day. Physical therapy is also very important. This, as with ankle sprains, can be done to strengthen the tendons.

If there is a tear, meaning a split that runs along the length of the tendons, surgery could be recommended for repairing the tendon. Sometimes, making the groove in the back of the bone of the fibula deeper allows the tendons more space and can help as well. Finally, if the tendon is very bad, one may need to resect the tendon and connect both the longus and brevis together. Only the specific tendon involved should be addressed. Occasionally, both may be involved.

Peroneal Tendonitis Complications

​​If the tendonitis is not addressed, tearing of the tendon can occur. Also, weakness of the tendons can lead to an ankle sprain. In the case of surgery, infection can develop. Nerve damage can occur if the sural nerve which runs along the side of the foot and provides sensation to the foot is cut or stretched. Instability itself can lead to many sprains which can damage the cartilage on the inside of the ankle.