What Is Peroneal Tendinosis?

The peroneal tendons run on the outside of the ankle just behind the bone called the fibula. Peroneal tendinosis is enlargement and thickening with swelling of these tendons. This usually occurs with overuse, such as a repetitive activity that irritates the tendon over long periods of time. 

Symptoms

People with peroneal tendinosis typically have either tried a new exercise or have markedly increased their activities. Characteristic activities include marathon running or others that require repetitive use of the ankle. Patients usually have pain around the back and outside of the ankle. There usually is no history of a specific injury.

Causes

Improper training or rapid increases in training and poor shoewear can lead to peroneal tendinosis. Also, patients who have a high arch may be more susceptible because their 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 patients are to develop tendinosis.

Anatomy

Tendons connect muscle to bone and allow them to exert their force across the joints that separate bones. Ligaments, on the other hand, connect bone to bone. There are two peroneal tendons that run along the back of the fibula. 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 bone called the fibula on the outside of the leg and connects to the fifth metatarsal on the side of the foot.

The peroneus longus takes its name because it has a longer course. It starts higher on the leg and runs all the way underneath the foot to connect to the first metatarsal on the other side. Both tendons share the major job of turning the ankle to the outside. The tendons are held in a groove behind the back of the fibula and are covered by a ligament-type tissue called a retinaculum.

Peroneal tendons

Diagnosis

Your foot and ankle orthopaedic surgeon will take your history and perform an exam to make the diagnosis. Most patients with peroneal tendinosis will report overuse of activity, rapid increase in recent activity, or other training errors, along with pain in the back and outside of the ankle. During the exam, there often is pain when the surgeon touches the peroneal tendons.

It is important to distinguish this from pain over the fibula, which might indicate a different problem (e.g., stress reaction of the bone). Pain on the fibula occurs directly over the bone. Pain in the peroneals occurs slightly further behind. There also is pain when you turn the foot inside towards the middle of your body (inversion). You may also have weakness in trying to bring the foot to the outside (eversion). The surgeon also will look for the varus posturing of the heel, which means that the heel is turned inwards. This can predispose a patient to the problem. X-rays for peroneal tendinosis usually are normal. Ultrasound is a very effective and way to assess the tendons and can show an abnormal appearance or tear. An MRI also may be used to show a tear. 

Treatments

The vast majority of peroneal tendinosis cases will heal without surgery. This is because it is an overuse injury and can heal with rest. If there is significant pain, wearing a CAM walker boot for several weeks is a good idea. If there is no tenderness with walking, an ankle brace might be the next best step. You should limit how much you are walking or are on their feet until the pain improves. This usually takes several weeks. After this period you can resume training, but very slowly and based on pain. For patients with hindfoot varus, an orthotic that tilts the ankle to the opposite side may help relieve pressure on the tendons. It is important to talk to your doctor about changing your training. This includes using new shoes for running or cross-training instead. Physical therapy also is very important to strengthen the tendons.

There is some interest in using platelet-rich plasma (PRP) or amniotic tissue to help stimulate healing growth. Currently, there are no studies showing that this works for the peroneal tendons. Steroids probably are best avoided as they can actually damage tendons.

Surgical treatment is indicated if the pain does not get better with rest. Non-surgical treatment could last up to a year before considering surgery. If there is a tear, meaning a split that runs along the length of the tendons, one could consider cleaning it out and 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, a surgeon 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.

Recovery

Patients usually recover fully but this can take considerable time. You must be patient and allow the tendon to heal before going back to activity. If you need surgery, your recovery time may be substantial. You may be instructed not to bear weight for about six weeks. Your foot and ankle orthopaedic surgeon likely will order physical therapy once you're ready. 

The outcome usually is good. However, sometimes it takes time for people to get back to their activity. When a tear develops and there is chronic thickening of the tendon, the outcomes are not as good. 

Risks and Complications

If the tendinosis is not addressed, the tendon can tear. 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.

FAQs

What is the difference between tendinitis and tendinosis?
Not much. Tendinitis implies that there is inflammation in the tendons. This usually happens directly after an injury for a short period of time. Tendinosis is a chronic process of pain in the tendons that results in an enlargement and thickening of the tendon.

 

Original article by Scott Holthusen, MD
Last reviewed by David Garras, MD, 2018

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