The Peroneals: Anatomy and Function

By Nicole Nelson
October 1, 2012

The Peroneals: Anatomy and Function

By Nicole Nelson
October 1, 2012

The peroneals are a fascinating group of muscles which largely go unnoticed unless you've sprained your ankle. Many of us have two peroneal muscles, some of us have three: Peroneus longus, peroneus brevis, and the occasional individual has peroneus tertius. Peroneus Longus is responsible for everting the foot and helps with plantar flexion of the ankle (think bringing the outside of your foot off the ground while pointing your toes. This muscle attaches proximally on the upper fibula and wraps behind lateral malleolus (aka ankle), continues along the underside of the foot where it attaches distally on the first metatarsal and medial cuneiform. Peroneus brevis also everts the foot and assists in plantar flexion of the ankle. It lies deep to longus and attaches proximally at the lower portion of the fibula. Peroneus brevis wraps behind the lateral malleolus and attaches distally on the fifth metatarsal. Peroneus tertius is an everter of the foot; but unlike the other peroneal muscles, it assists in dorsiflexion of the ankle. Its proximal attachment is on the anterior distal fibula and runs anterior to the ankle, attaching distally to the 5th metatarsal.

Although the peroneals are chiefly regarded as everters of the foot, a lesser known, yet very cool fact about the peroneus longus muscle is that it helps in the stabilization of the big toe. This stabilization plays a large role in the appropriate winding of the plantar fascia during gait, known as the windlass effect. Any individual that is forced to move laterally (i.e. tennis or basketball player) places a high demand on these muscles as they act to stabilize and prevent inversion of the ankle. Running or walking on uneven surfaces such as a trail or soft sand will also challenge these muscles. When life is good, the peroneals, along with tibialis anterior and posterior, control inversion and eversion of the ankle and keep the structures of the foot and ankle out of harms way. As we all know, life isn't always good and injury results. Let's take a look at the peroneals involvement in ankle instability and go over some massage strategies that will help our clients reduce their pain possibly prevent future injury.

Ankle Sprains

Ankle sprains are the most common athletic injury, with approximately 30,000 sprains per day in the U.S. (DiGiovanni et. al. 2004). Approximately 90% of these ankle injuries are inversion sprains. To make matters worse, 70% to 80% will suffer a subsequent ankle sprain (Yeung 1994). The potential for recurrent sprains is a likely consequence of structural trauma of the ligaments of the ankle, as well as decreased proprioceptive feedback and peroneal weakness (Lofvenberg et al 1995). This scenario creates the potential for chronic ankle instability and further weakening of the peroneal muscles. It seems that the feedback loop that communicates the location of the foot to the brain is off. Without this input, the brain is somewhat blinded to the local environment leaving the peroneal firing patterns ill-timed. This is problematic as the peroneals need to fire in an anticipatory manner in order to correct balance and absorb the impact of foot striking.

Muscle Imbalance

Now let's discuss some of the causes behind weakness of the peroneals. There are many reasons why peroneals become dysfunctional including structural anomalies of the foot and ankle, tendon subluxation, nerve entrapments and tendon tears. Given the complex nature of the ankle and foot, clients with pain in this area should be encouraged to see a physician before you begin any massage treatment. As soft tissue experts, we are looking at the fascial and muscle structures and possible nerve entrapments that may be causing peroneal issues. Vladamir Janda suggested that certain muscles have the potential to shorten and tighten (tonic muscles), while others tended to lengthen and weaken (phasic muscles). Janda's observations led him to put the peroneals in the phasic camp, suggesting that these muscles are prone to inhibition. This inhibition creates an environment of ankle instability.

On the other hand, Janda characterized the posterior tibialis, gastrocnemius and soleus muscles as tonic in nature. This imbalance of the lower leg not only destabilizes the ankle, but opens the door for other problems including plantar fasciitis, compartement syndromes, calcaneal bone spurs and achilles tendinosis. Additionally, the faulty movement patterns which result from the imbalance will create compensations that will surely travel up the kinetic chain and likely cause hip, lower back and neck issues.

Assessment and Treatment

As we all know, successful therapy begins with assessment and intake. If your client has had a history of ankle sprains and they mention discomfort around the ankle and/or along the lateral lower leg, the peroneals should be suspected as an area of issue. Let's go over a few treatment ideas for a client that has a history of ankle rolling and ankle pain.

Don't chase the pain! Given the peroneals propensity for weakness and the high percentage of inversion type sprains, I would caution against deep stripping and stretching of this group. I certainly do suggest relieving trigger points in these muscles with local compression. I would also recommend cross fiber friction to the areas that feel particularly glued down. For this work, I usually position clients in a sidelying position, with the involved leg up and bolstered. Sherrington's law of reciprocal inhibition states that a hypertonic antagonist muscle may be reflexively inhibiting it's corresponding agonist. If we consider this law in conjunction with Janda's insights, it stands to reason that most of the deep stripping should be performed on the posterior tibialis, gastrocnemius and the soleus muscles. Additionally, contract/relax methods of stretching will be helpful in normalizing these overly tightened tissues. Naturally, not everyone fits into the tonic/phasic mold outlined by Janda; therefore, each client should be assessed and evaluated for their unique set of tightness and restrictions.

Enlist the help of a corrective exercise specialist. According to DiGiovanni, the gold standard for ankle instability issues includes the RICE protocol, early range of motion, progressive weight bearing, peroneal strengthening as well as proprioceptive training (DiGiovanni et al 2006). This is supported by studies done by Holme and others. Their research reports that clients with a history of ankle sprains were twice as likely to suffer recurrent sprains if they did not engage in a balance and strengthening program (Holme et al 1999). This aspect of treatment will require you to pair up with someone with corrective exercise experience. A well directed strength program is an absolute necessity in order to restore balance to the stirrup musculature, improve proprioception and reclaim proper biomechanics.

Check the client's footwear. Unfortunately for clients with peroneal issues, their choice of footwear should come under some scrutiny. It is well known that elevated heels present a challenge to the body's ability to oppose gravity efficiently and places a wrench in optimal alignment and proper biomechanics of the ankle. Now, what about flip-flops? Sorry to put a crimp in casual Friday footwear, but these shoes probably present a greater threat to the foot than any type of high heel. Flip-Flops disrupt the windlass effect of the foot. When the windlass effect is in effect the big toe should dorsiflex; however, when wearing flip flops, the big toe actually plantar flexes in order to grab the flip-flop and prevent it from slipping off the foot. In other words, walking in flip flops encourages poor motor patterning of the muscles of the foot, including one of the big toe stabilizers, peroneus longus.

To sum it up, peroneal weakness and ankle sprains are closely linked and all too common. A little attention to these muscles will hopefully limit the muscle imbalance of the ankle and foot and help prevent future sprains.


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