Introduction

Peroneal tendonitis is one of the three commonest ankle disorders, along with peroneal subluxation and peroneal tears. These disorders affect the peroneal tendons, which are located on the outside of the ankle. Ankle instability is the main complication of peroneal tendonitis.¹

The management of peroneal tendonitis includes several approaches, from the use of anti-inflammatory drugs to surgery. Latest research has focused on alternative treatments, often used for tissue healing and repair, such as Platelet-Rich Plasma (PRP) therapy.¹

PRP therapy consists of extracting the plasma from one’s own blood and injecting the platelet-rich fraction back into the target tissue. PRP is well-known for its uses in medical esthetics including:

• Reduction of wrinkles
• Improvement of skin elasticity and moisture
• Promotion of hair growth

However, PRP therapy has a much larger application field due to the set of growth factors that it provides and has proven useful in other settings of human health.² Growing interests in new treatments led to the development of a handful of studies on PRP therapy for tendon disorders in recent years. This makes PRP therapy one of the most interesting emerging alternative treatments. 

What is peroneal tendonitis?

Peroneal tendonitis, also known as tenosynovitis, is a condition characterized by painful and chronic inflammation of one or more peroneal tendons. This disorder is most often diagnosed in active young people.¹

The ankle has a set of two tendons that provide support and guarantee joint mobility by connecting muscles to bones. The peroneal brevis tendon originates from one side of the fibula (thinner bone of the leg) and ends in the foot at the fifth metatarsal, which is the largest bone in the foot, right before the pinky toe The peroneal longus tendon starts on one side of the tibia (thicker bone of the leg) and the fibula, and ends in the foot at the first metatarsal, which corresponds to the big toe.³ 

Both tendons are located on the outer side of the ankle and help the foot move in their direction, meaning to the outer side of the body. This movement is called eversion and is essential for proper walking.

Some people may have an additional tendon called the peroneus quartus, which could be confused with a tendon tear if not previously known.³

A. Distal peroneus brevis tendon inserting into the base of the fifth metatarsal. B. Peroneus longus tendon. C. Space between the longus and brevis tendon at the peroneal tubercle. Taken from.³

Minor injuries of the peroneal tendons usually happen due to inversion ankle injuries, meaning sudden and hurtful inner bending of the ankle. Overuse, along with incomplete or faulty healing, may cause long-term inflammation, which receives the name of peroneal tendonitis.^1,3 

As stated above, active young people are the population that most commonly suffer from peroneal tendonitis, and, among them, 88% have peroneal brevis tendon tears, followed by tears in both tendons in 37%, and 13% with only peroneal longus tears.¹

People usually seek medical advice due to non-resolving, long-lasting pain or difficulty in performing activities or exercise that involves weight-bearing. Other common symptoms include:^1,3

• Swelling
• Tenderness behind the ankle bone
• Pain over the side of the foot
• Ankle instability

Conventional treatment options

Your physician may choose to handle peroneal tendonitis through conservative measures that allow time for healing, unless you are experiencing severe pain and inflammation. In that situation, you may be referred to an orthopedic surgeon or a similar specialist.¹

The initial approach includes rest and restriction of movements that may compromise the tendon recovery such as:¹

• Twisting
• Bending
• Walking on uneven surfaces

In some instances, joint immobilization may be necessary in combination with:¹

• Ice pads
• Anti-inflammatory medications
• Physical therapy

When the pain and inflammation do not improve, physicians may suggest corticosteroid injection. In people with large-extent inflammation, corticosteroids may also be needed to aid proper imaging during the diagnosis process.¹ 

You should follow and apply these measures for 4 to 6 months to accomplish full resolution of tendon inflammation. People who continue experiencing ankle instability after that period of time may be candidates for surgery.¹

What is Platelet-Rich Plasma (PRP) therapy?

Your blood could be seen as a liquid tissue: a liquid matrix full of salts and proteins in which several types of cells get transported to every corner of your body.

When blood is drawn and spun at high velocity (centrifuged), all its heavy contents sink to the bottom of the collection tube, leaving two clearly different layers. The lower layer, or hematocrit, contains all the red blood cells along with white cells from our immune system. In contrast, the top yellow layer, or plasma, contains proteins and cell fragments. Most of those cell fragments correspond to platelets or thrombocytes. Their main function is forming blood clots to prevent excessive blood loss in the face of an injury.⁴

After centrifugation, the heaviest content of both blood layers moves to the bottom, meaning that as we move to the bottom of the plasma layer, there will be more and more platelets and big proteins. That bottom-most and thickest fraction of the plasma layer is what specialists call platelet-rich plasma, or PRP.⁴

The use of plasma has gained big interest in previous years, and this is especially true for PRP, whose injection is expected to help with tissue repair by optimizing the body’s natural healing with extra proteins and growth factors.⁴

Laboratory and animal studies reveal that PRP injection may help with tendon injuries by:⁴

• Increasing tendon cell division 
• Improving collagen production
• Reducing inflammation

PRP therapy was first described in the 1970s to treat people with blood disorders. However, in the following decades, its uses extended to several other fields, with medical esthetics being the most recent and well-known.² In orthopaedic surgery, PRP therapy has turned into a routine tool. Indeed, about 86,000 athletes in the United States and Europe with acute and chronic tendon, ligament, and muscle injuries have been treated with PRP therapy.^2,4

How PRP therapy works for peroneal tendonitis

PRP therapy is a standardized procedure, fine-tuned after several years of application in several settings. It consists of the following well-known steps:⁵

• Blood collection: around 30 mL of venous blood is drawn 
• Blood centrifugation: The blood sample is spun at high speed (about 620 g) for 15 minutes, and the lower plasma layer, or PRP, is extracted through a syringe
• Anesthesia application: Local anesthesia is applied close to the area that PRP will be injected 
• PRP tendon injection: recently extracted PRP is injected into the affected tendon. For precise administration, specialists may use ultrasound guidance

What does the research say?

Studies so far have shown conflicting evidence about the benefits of PRP therapy for the management of tendon injuries and disorders. While some found that PRP therapy was superior to anti-inflammatory drugs, others did not find any benefit.⁵

In the largest available study, 408 people received PRP injections inside the affected tendons guided by ultrasound imaging. Researchers followed up the patients and 23 of those who had peroneal tendonitis for 6 weeks or more reported an improvement in tendon function and reduction in injury size.⁵

In all these studies, PRP therapy was considered safe; however, more studies are needed to confirm its benefits and support its inclusion as a regular approach in sports medicine and orthopedic clinics.

Who might benefit from PRP therapy?

Studies suggest that PRP therapy may help with peroneal tendonitis and other musculoskeletal conditions, such as:⁵

• Tennis elbow
• Plantar fasciitis
• Achilles tendinopathy

However, PRP therapy lacks supporting evidence and, thereby, may not be ideal for: 

• Acute injuries
• Severe tendon tears

Risks and side effects of PRP therapy

When performed under hygienic conditions by a well-trained healthcare professional, PRP therapy is safe. However, patients may experience minor, bothersome but temporary effects, such as:⁵

• Mild inflammation and pain at the PRP injection site
• Poor or minimal response to PRP

Summary

• Peroneal tendonitis is the painful inflammation of the peroneal tendons located over the outer side of the ankle
• It mainly occurs in young active adults and is a result of ankle injuries or overuse
• Pain, swelling and instability of the ankle joint are common symptoms of the condition
• Conventional therapy for peroneal tendonitis include rest, pain relief, immobilization and steroid injections
• Platelet Rich Plasma (PRP) therapy is an upcoming, minimally invasive alternative treatment for managing peroneal tendonitis
• PRP therapy involves centrifuging blood to concentrate plasma and platelets, which is then injected into the peroneal tendons
• PRP is thought to help with tendon repair due to the presence of high levels of growth factors that improve collagen production and reduce inflammation
• Side effects of treatment are usually only minor and include pain and swelling of the injection site
• While not a guaranteed solution, as research only shows limited evidence, it offers hope for those who haven’t responded to conventional treatments.
• It is important to consult a specialist for proper healthcare advice before trying PRP therapy