The Anatomy of the Peroneus Longus Muscle

Moves and Stabilizes the Ankle

Anatomical photo of the lower leg.
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In This Article

The peroneus longus muscle is a major mover and stabilizer of your ankle. The muscle, along with the peroneus brevis and tertius, courses down the lateral side of your lower leg and attaches to your foot. It serves to move your foot and ankle in various directions. Injury to the peroneus longus can cause pain, decreased motion, and difficulty with basic functional tasks such as walking and running. The peroneus longus is also known as the fibularis longus.

Anatomy

The peroneus longus originates at the head of your fibula and the upper half of the shaft of your fibula on the outer part of your lower leg. It then courses down the lateral part of your leg with peroneus brevis and tertius, turns into a tendon, and attaches on the bottom of your foot at the medial cuneiform bone and first metatarsal bone.

The muscle is considered an extrinsic ankle muscle; it originates in your leg and attaches to your foot and serves to move your ankle. The tendon of peroneus longus (along with peroneus brevis) are held in place near your lateral ankle by the superior peroneal retinaculum, a thick band of tissue.

Peroneus longus is a superficial muscle that can easily be seen and palpated. As you move your ankle into eversion (rotating your ankle outward), you can see the muscle contract beside your calf.

Nerve supply to the peroneus longs is via the superficial peroneal nerve that arises from lumbar level five and sacral level one and two. Blood supply comes from the anterior tibial and peroneal arteries.

Fun Fact

The official name of the muscle was changed from peroneus to fibularis to avoid confusion with another anatomical structure, the perineal area. (The perineal area is the anatomical area between your anus and scrotum or vagina.) You can imagine the confusion that could occur if your doctor is directed to inspect your peroneus muscles and ends up checking your perineal area. Alas, anatomical name changes occur slowly over time and the traditional peroneus name continues to be used.

Function

The peroneus longus courses down the lateral aspect of your lower leg and attaches around the lateral foot and on the bottom of your foot. When it contracts, it moves your ankle into eversion. This motion is when your ankle moves to the side towards your smallest toe.

The muscle also assists the gastrocnemius (calf) muscle in plantar flexing your foot, as in pointing your toes down. Peroneus longus also supports your transverse arch in your foot. When you are standing on one foot, the muscle helps to stabilize your lower leg on your ankle, maintaining balance.

The peroneus longus is a strong muscle and its associated tendon is able to withstand the high forces that may occur during walking and running. Due to its high tensile strength, it occasionally is used during knee surgery as a harvested anterior cruciate ligament graft. Research shows that it can be removed from your lower leg and used as a knee ligament without causing significant loss in foot and ankle function.

Associated Conditions

Injury to the peroneus longus muscle may cause pain in your lower leg, ankle, or foot. Various conditions may affect the muscle and cause difficulty with walking or running. Conditions that may affect the peroneus longus may include:

  • Peroneal tendonitis. This occurs when the long tendon of the peroneus muscle becomes inflamed and irritated. This may occur due to overuse, or the peroneal tendon may be pinched beneath the bone that is courses under. Pain on the outer portion of your foot and ankle may result making it difficult to walk or run normally.
  • Peroneus longus muscle strain. If a forceful motion of your foot or ankle occurs, your peroneal muscles may be overstretched, leading to a strain. Strains may range in severity from a mild overstretch to a full-thickness tear of the peroneus muscle. Peroneus longus strain may result in lateral leg pain, swelling near your ankle, and difficulty walking and running.
  • Peroneal tendon subluxation. If your foot is forcefully moved into dorsiflexion or inversion, the peroneal tendons may become overstretched and the retinaculum that holds them in place may become damaged. This may result in tendon subluxation; the peroneus longus tendon moves out of place behind the lateral malleolus of your ankle and then snaps back into place. This may or may not be accompanied by pain or discomfort.
  • Ankle sprain. The most typical motion of an ankle sprain is when your foot moves suddenly into inversion and your ankle rolls over laterally. This may damage the lateral ligaments of your ankle and may overstretch your peroneal tendons. The peroneus longus may become irritated as a result.
  • Weakness due to a pinched spinal nerve. The nerve that innervates your peroneus longus emerges from your low back, and a problem there from arthritis or a herniated disc may cause the nerve to become pinched. This may result in pain in your lower leg and weakness in the muscles that move your ankle. Sometimes, the peroneus longus muscle (and the tibialis anterior) may be weakened as a result, leading to foot drop and difficulty moving your ankle normally.

If you are having pain in your lower leg, check in with your physician to get an accurate diagnosis and start on the right treatment.

Rehabilitation

If you have a peroneus longus injury, you may benefit from working with a healthcare professional, such as a physical therapist (PT), to help you fully recover. Various treatments for peroneus longus injuries may include:

Rest

Rest can be beneficial by allowing your peroneus longus tendon to heal properly. Depending on the severity of your injury, rest may last from three days to several weeks. If the muscle or tendon are torn, you may be required to immobilize your ankle in a cast or removable walking boot.

Heat or Ice

If you have suffered an acute peroneal tendon injury, you may benefit from applying ice to the affected area to control inflammation. Ice should be applied for 10 to 15 minutes several times each day. A few days after the injury, heat may be used to promote circulation. Heat can be applied for 10 minutes. Care should be taken when using ice or heat to avoid skin irritation and burns. Your PT can show you the best way to apply heat or ice.

Neuromuscular Electrical Stimulation (NMES)

If you have peroneus longus weakness due to injury or from a pinched nerve, your PT may use neuromuscular electrical stimulation (NMES) to promote proper muscular function and contraction. The NMES artificially contracts your muscle, helping it to function properly.

Low Back Exercises

If a pinched nerve is causing peroneus longus weakness or pain, performing lumbar stretching exercises lumbar stretching exercises may help get pressure off the nerve. Prone press-ups, side glides, or lumbar flexion may benefit a pinched nerve. Which one is right for you? Your local PT can help you decide.

Stretching Exercises

After a peroneus longus injury, your healthcare provider may prescribe stretching exercises for your ankle and lower leg. The runner's stretch may be used to stretch your calf and soleus muscles, and ankle alphabet exercises where you draw letters with your ankle can help improve ankle range of motion.

Peroneus longus stretching involves moving your foot and ankle into inversion to place the peroneal muscles on stretch. Hold the stretched position for 15 seconds and then rest. This can be repeated three to five times. Overpressure may be added by using a towel to gently pull your foot inwards, thereby providing extra stretch to the peroneal tendons on the lateral side of your foot and ankle.

Strengthening Exercises

If your peroneus longus is weak, strengthening exercises may be performed. To do this, simply move your foot outwards into eversion. Hold the position for 5 seconds, and then rest. Repeat 10 to 15 times.

Addition of a resistance band around the ball of your foot can add extra challenge. Simply use your other foot to hold the band in place, and then move your ankle out to the side and into eversion.

Since the peroneus longus also functions to point your toes, performing calf raises can also help strengthen the muscle. Simply stand with the balls of your feet on the edge of a step and rise up onto your toes. Hold the position for a few seconds, and then slowly lower yourself down. Perform 10 to 15 repetitions.

Balance and Proprioception Exercises

Since the peroneus longus helps to stabilize your ankle and foot when walking, it may be helpful to work on improving balance and proprioception as part of your peroneus rehab program. (Proprioception is how a body part tells your brain where it is and what position it is in.)

A simple progression of single leg standing may be prescribed. To start, hold onto something stable and stand on one foot. If you can hold this for 30 seconds, perform the exercise without holding on. When this becomes easy, perform the exercise while holding something stable, but keep your eyes closed while balancing. Finally, stand on one foot with no upper extremity support and keeping your eyes closed. To make the single leg standing exercise more challenging, stand upon something unstable such as a couch cushion or a pillow.

Massage

After a peroneus longus injury or with tendonitis, massage may be used to promote circulation and decrease muscle pain. Massage can also help to improve tissue mobility of the muscle and may be used prior to stretching. Massage to the peroneals should not be painful; gentle strokes of progressive intensity is enough to promote movement and circulation in your peroneus longus.

Shoe Orthotics or Inserts

Sometimes, poor foot position can place excessive stress on your peroneus longus muscle, leading to pain and difficulty walking. Your physician may recommend using inserts in your shoes to help support the arch of your foot. This may give your peroneus longus some help keeping your foot in the right position and may decrease pain.

Injections

If you have persistent peroneus longus pain due to inflammation, you may benefit from a steroid injection to relive the pain. The steroid is a powerful anti-inflammatory medication that can reduce tendon pain and swelling.

A newer procedure called platelet rich plasma (PRP) injection may also be helpful in relieving peroneus longus pain. During PRP, blood is drawn from your body and is spun in a centrifuge to obtain the platelets and plasma. Then, the platelets are mixed with a small amount of plasma and are injected into your tendon. This signals your body's immune system to release white blood cells and growth factors to begin healing the injured tendon. PRP injections are touted as helping your body heal itself. Research continues to be done on PRP therapy and its efficacy in the treatment of tendon injuries.

Surgery

If you have suffered a peroneus longus tendon or muscle tear, surgery may be an option to repair the damaged tissue and restore normal function of the muscle. Surgery involves making an incision on the lateral side of your leg and using sutures to sew the injured muscle and tendon tissue together. After surgery, you should expect to be immobilized for a few weeks while things are healing. After a period of immobilization, starting gentle range of motion, stretching, and strengthening may be in order to regain full mobility of your peroneus longus.

Visit your physician if you suspect you have any injury to your lower leg or peroneus longus muscle. If you are performing any exercise for your peroneus longus, you must see a professional before starting. Stop exercising if you feel increased pain.

A Word From Verywell

The peroneus longus is an important muscle in your lower leg that serves to evert and flex your ankle. Injury to the muscle can cause pain and limited ability to walk or run. Understanding the function and anatomy of the peroneus longus can help you make the best choices for your care if you have suffered and injury there.

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