The peroneus brevis tendon is a rope-like structure located on the outer side of the lower leg and ankle, forming a crucial part of the body’s defense against ankle sprains. It is one of two primary tendons in the lateral compartment of the leg, alongside the peroneus longus tendon. These paired structures belong to the fibularis muscle group, which plays a major role in stabilizing the foot and controlling its movement. Proper function of this tendon is important for maintaining balance, especially when navigating uneven terrain.
Anatomical Location and Course
The peroneus brevis tendon begins as a muscle belly that originates from the lower two-thirds of the fibula, the thinner bone on the outside of the lower leg. The muscle belly of the peroneus brevis lies deep to its longer counterpart, the peroneus longus, as it travels downward toward the ankle. As the muscle transitions into its tendon, it courses directly behind the lateral malleolus, the outer ankle bone.
The tendon is secured in a groove behind this bony landmark, sharing a common sheath with the peroneus longus tendon. This structure is held in place by dense connective tissue called the superior peroneal retinaculum. From the ankle, the tendon runs forward along the outer side of the calcaneus, or heel bone, positioned superiorly (above) to the peroneus longus tendon. Its course terminates where it inserts into the tuberosity, located at the base of the fifth metatarsal bone on the outer edge of the foot. This attachment point is relevant to certain foot injuries, as a strong contraction can sometimes pull a piece of this bone away, resulting in an avulsion fracture.
Primary Function in Foot Movement
The primary action of the peroneus brevis is eversion, the movement that turns the sole of the foot outward. This action is essential for adapting to changes in the ground surface, such as walking on uneven terrain.
The peroneus brevis also assists in plantar flexion, the action of pointing the foot and toes downward. These combined actions contribute significantly to the dynamic stability of the ankle joint. By helping to stabilize the lateral ankle, the muscle group actively resists the excessive inversion forces that are the most common cause of ankle sprains. The muscle is constantly engaged in steadying the leg upon the foot, especially during activities that involve single-leg stance or rapid side-to-side movements.
Common Conditions Affecting the Peroneus Brevis
The peroneus brevis tendon is exposed to a variety of injuries, with the most common being Peroneal Tendinopathy, which describes inflammation or degeneration of the tendon. This condition is often an overuse injury, often seen in athletes, due to repetitive stress and friction behind the lateral malleolus. Biomechanical factors, such as having a high arch, can also increase strain on the tendon, making it more susceptible to degenerative change.
Another issue is an Acute Tear, which can be partial or complete, and is frequently misdiagnosed as a routine lateral ankle sprain. These tears often occur following a forceful inversion injury, where the tendon is stretched or damaged as it tries to prevent the foot from turning inward. The peroneus brevis is particularly susceptible to longitudinal tears (splits running along the length of the tendon) because of its flatter shape and its position closer to the bone of the fibula.
A third condition is Peroneal Tendon Subluxation, where the tendon slips out of its groove behind the lateral malleolus. This often results from a traumatic event that tears the superior peroneal retinaculum, the fibrous band that holds the tendon in place. When the tendon subluxates, individuals report a painful snapping or popping sensation along the outside of the ankle during movement. Chronic ankle instability, resulting from previous sprains, is a risk factor for this recurrent tendon displacement.
Non-Surgical Treatment and Rehabilitation
For non-acute injuries like tendinopathy, initial non-surgical management focuses on reducing pain and inflammation. This involves rest, activity modification, avoiding movements that cause pain, and using ice to manage swelling. Short-term immobilization with a walking boot or ankle brace may be used to decrease mechanical stress on the injured tendon, promoting healing.
Once pain has subsided, a structured physical therapy program begins, aiming to restore strength and range of motion. A primary goal is strengthening the peroneal muscles through targeted exercises, such as using a resistance band to perform eversion movements. These exercises gradually increase the tendon’s ability to tolerate stress and improve its power to stabilize the ankle.
Rehabilitation also incorporates exercises to improve proprioception (the body’s sense of joint position and balance). This often involves single-leg stance work on stable and then uneven surfaces. Flexibility and core stability exercises may also be included to address any underlying biomechanical issues that may have contributed to the injury. The progression of the program is carefully monitored, ensuring that exercises are tolerable and do not cause a flare-up of symptoms, allowing a gradual return to higher-level activities.