Introduction

Where and What is the Peroneal Tendon?

First, let's start with what a tendon is! A tendon is like a rope connecting a muscle to a bone. It helps provide the tension needed to create movement. There’s not just one peroneal tendon, there are two! The names of these two tendons are the peroneus longus and brevis. They both run alongside each other down the outside of the calf, wrapping around that little bony lump on the outside of your ankle (the lateral malleolus) and extending into the foot. The short one (the peroneus brevis) ends at the outside of the foot at the base of the fifth metatarsal (the long bone right before the pinky toe). The long tendon (peroneus longus) extends under the foot into the arch.¹ The main function of these two tendons is to help support and stabilize the ankle. They also help turn the foot, which can be important while walking, especially on uneven surfaces.¹

Figure 1: This photo shows the anatomy of both the peroneus longus (left) and brevis tendons (right).⁸

What is Peroneal Tendonitis?

Tendonitis occurs when friction, or rubbing against a tendon, causes it to become irritated or inflamed. It can be caused by various reasons, which we will get into later in this article, and can be a very frustrating and painful condition if not properly treated.¹ Peroneal tendonitis refers to the condition in the acute phase, whereas peroneal tendinopathy refers to the condition that has become chronic.³

If a patient does not seek treatment and continues physical activity, they are placing themselves at a very high risk of tearing their peroneal tendon. This is a much more serious condition that may require surgery to fully recover. This is why it is ESSENTIAL to speak to a healthcare professional if you or a loved one believes you may be suffering from peroneal tendonitis.¹

Who does it normally affect?

Indeed, runners are often the group of patients most commonly affected by this condition. Typically, we find it more in endurance, or long-distance runners compared to sprinters or short-distance runners. It is also frequently seen in dancers, skaters, cheerleaders, skiers, and even horseback riders. The commonality between all these sports is frequent, cyclic muscle contractions of the ankle.³

Fortunately, peroneal tendonitis is not as common as some other forms of tendonitis, such as Achilles tendonitis. Studies have shown when looking at a group of 1,000 runners, only 1% of them suffered from peroneal tendonitis throughout that study.² However, just because it is rare doesn’t mean it's difficult to treat. Tendonitis, no matter where it is in the body, tends to follow a similar treatment pattern, which we will dive into later in this article 

Peroneal tendonitis usually affects individuals who perform any activity with a lot of movement at the ankle. This would mostly be seen in athletes, specifically runners.¹ However, peroneal tendonitis doesn’t just affect these highly skilled athletes; it can also affect a novice who has recently had a steep uptick in their physical activity. Other triggers include overuse, improper technique, poor footwear, previous ankle injuries or surgeries, smoking, obesity, diabetes, or prolonged use of steroids.¹ 

What are some signs and symptoms of peroneal tendonitis?

As always, you should consult a specialist for an official diagnosis and treatment. However, some signs and symptoms of an injury to the peroneus longus or brevis include pain and/or swelling on the back or outside of the ankle, pain when moving the foot, instability of the ankle, and pain that worsens with activity but improves with rest.¹

Overuse as a primary cause

When overuse is the cause, it is important to note that rest is one of the key treatments for this condition. It is essential to avoid walking and any other aggravating activities until symptoms have completely resolved.¹ The classic treatment for these kinds of conditions includes the “RICE” method (rest, ice, compression, and elevation). Depending on the severity of injury, the patient may be placed in a boot, a lace-up ankle brace, or a supportive wrap. Pain medication, like anti-inflammatories, may be used as well.¹

One of the reasons athletes can be so prone to these injuries is due to the types of movements they are expected to perform. Cutting, blocking, juking, and lateral movements requiring a sudden change in direction can lead to peroneal tendonitis.⁶ This is why with the trend of people playing pickleball we have seen a recent uptick in these types of injuries, especially considering patients over the age of 40 are at higher risk of developing problems with peroneal tendonitis. 

Just like athletes can sustain injuries from overuse, people who are poorly conditioned can see similar injuries when there has been a sudden increase in physical activity.¹ We see this a lot in our New Year's resolution makers who suddenly decide to commit to the gym! 

Repetitive strain

Repetitive injuries cause multiple episodes of stress and stretching on these tendons. These microtraumas delay the ability of this tendon to heal as it would normally, turning what would have been an acute condition into a chronic one.⁴ The most common movements that can cause these microtraumas are eversion, rolling the foot outward, and plantarflexion, or pointing the foot down. The picture attached below will show you what each of these movements look like so it will be easier to visualize it. 

Figure 2: shows the medical terminology used to describe different movements at the ankle. Both eversion and plantarflexion are known as some of the most common causes of peroneal tendonitis.⁵ 

Poor footwear is also known to be a common culprit in these types of peroneal injuries. Wearing shoes such as sandals can be unsupportive and lead to these conditions. While tennis shoes may be more ideal, if they are not well made or do not fit appropriately they can cause issues.⁴ Use of improper footwear can be further exacerbated by walking on uneven surfaces. Switching your flip flops out for tennis shoes, particularly those with a slight heel, provides much more support for the peroneals compared to flat shoes like flipflops.⁴

Biomechanical contributors

Foot structure abnormalities

One of the most common risk factors for peroneal tendonitis is people who have high arches in their feet. The presence of these high arches can place excessive strain on the peroneal tendons, making them more likely to become inflamed with activity. ² It is often recommended to see a podiatrist to be evaluated for orthotic support which can help reduce strain on the peroneals and provide better support and stability of the foot.⁶

In the presence of issues with peroneal tendonitis only on one side, sometimes a leg length discrepancy can be the culprit. It is typically the shorter leg that is affected. In the shorter leg, the foot tends to rotate outwards to help compensate for the discrepancy. This places excessive stress on the peroneal tendons on that side.⁶

Muscle imbalances

Muscle weakness in the ankles and calves can be caused by a variety of reasons, not just a lack of training. We often see injuries like this occur while walking on uneven surfaces, or from travelers returning home from a European vacation where they were walking on cobblestone surfaces, for example. These uneven surfaces force us to use small muscles in our ankles for stability which are not commonly used in our day-to-day lives on flat surfaces. This can lead to overuse and strain of these tendons. One way to combat this weakness is through physical therapy and training; oftentimes use of elastic resistance bands can help.⁶
Tight calves can also place unnecessary stress on the midfoot and in turn, the peroneals. Thus, stretching before exercise is important, as is diversifying your training to not overtrain the calves.⁶ Oftentimes, physical therapy, or creating daily habits such as yoga, can help combat tightness of the muscles that can lead to injury.

Gait abnormalities

Just like a leg length discrepancy can change the way a patient places stress on their foot, so can habit. Some people may walk or run with a gait that is slightly out of alignment, typically in supination, leading to peroneal tendonitis. Runners who place more pressure on the inside of their foot result in more strain and stretching of the peroneals.⁶

Figure 3: This image demonstrates differences in alignment of the foot, comparing pronation and supination. In the setting of peroneal tendonitis, supination tends to be the culprit considering the excessive stretching and strain it places on the peroneals.⁷

Secondary or contributing factors

When it comes to footwear, it is essential to wear shoes that fit appropriately but also provide proper support to both the foot and ankle.¹ Stretching is also essential before physical activity considering it helps prevent injuries such as peroneal tendonitis. Thus, it is important to not forget to stretch both the calf and peroneal muscles first before performing any physical activity, especially for a person with a history of previous injury.¹

Even though the majority of the cases we have discussed in this article related to overuse or chronic issues, peroneal tendonitis can still occur during an acute injury like an ankle sprain or a fall. A lot of times this will cause either an “over-stretch” of the tendon or the sheath that surrounds the tendon can become inflamed making movement of these tendons much more difficult.²

Summary

Patients who suffer from peroneal tendonitis tend to make a full recovery! However, it is essential to listen to the suggestions of your healthcare provider to not prolong the healing process or do anything that may result in a more chronic problem. While it may be tempting to get back out there and play your sport as soon as you start feeling better, it is essential not to rush the process. According to the NHS, it can take anywhere from 3 months to a year to make a full recovery. Education about this condition is essential, considering it is a bit rare and uncommon. Studies have found that roughly 60% of patients with peroneal tendonitis were misdiagnosed at their first visit. Misdiagnosis can prolong healing times which is why it's essential to spread awareness about this condition.