Extrinsics – the peroneals

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One of the big things to remember as we make our way through the extrinsic muscles is that they ALL control not one, but two joints – the ankle (talocrural) joint and the subtalar joint. These two joints are essentially stacked right on top of each other. This is important because it’s the long tendons of the extrinsics that determine the position of the subtalar joint. Whether the muscle is stuck in a long or short position, it will 100% impact how the foot lands and how the ankle and foot function in terms of shock absorption, stability, and propulsion.

In other words, there will be compensation in the leg chain for problems in the extrinsics. In this regard, the peroneals are a perfect example of a compensation injury. Any time you have problems here, you should automatically be thinking about the why. If you simply fix the symptoms without fixing the why, you will be battling this for a long time or worse, something harder to fix will break. Before we dive into all of that, let’s talk anatomy!


There are two muscles along the outside of the lower leg- the peroneal longus and the peroneal brevis. However, you may remember from last weeks post that we talked about a third peroneal muscle located along the lower shin- the peroneal tertius. We’ll be including that muscle here again and explain why it’s important to remember! Just as a reminder- when it comes to these muscles the words “peroneal” and “fibularis” are used interchangeably. To me they will always be the peroneals, but I do use both. 🙂

#1 Peroneal Longus


  • Both the peroneal longus and peroneal brevis start along the fibula. The difference is that the longus starts on the upper half and brevis starts on the lower half. Both then wrap around behind the lateral malleous enroute to the fifth metatarsal.
  • The longus does not stop when it hits the outside of the foot however. It wraps under the cuboid and crosses all the way to first toe where it attaches to the first metatarsal and first cuneiform.
  • Like the other intrinsics, this muscle moves two joints. Essentially you have a long tendon with two big lever arms. By wrapping behind the ankle joint, it helps plantar flex the ankle (point the toes down). By wrapping under the outside of the foot, it everts the foot.


  • In addition to that long tendon, the PL also has two muscles that directly attach to it’s long tendon. The FDM works at the little toe and the AH works at the big toe. Restrictions in the peroneal will directly affect these two muscles and vice versa!
  • Mobility restrictions/trigger points in this muscle are the same as those for the brevis. There are two areas (the purple circles in the picture above).
  • Problems in this muscle are commonly misdiagnosed as lateral compartment syndrome and as referred nerve pain coming from the low back.
  • The video below will go over how to find/palpate this muscle, as well as, how to stretch it.

#2 Peroneal Brevis


  • As stated above, the PB sits on the lower half of the fibula. It wraps around the lateral malleolus with the PL tendon. However, it does not wrap under the bottom of the foot. It attaches to the outside of the fifth metatarsal.
  • Like the PL, this muscle is responsible for plantarflexing the ankle and everting the foot.
  • Like the PL, this muscle also shares the same pain referral areas and common misdiagnoses.
  • While it may be easy to write off this muscle as being the smaller, less important peroneal, that would be wrong. If the PL is restricted/stuck, then the PB will be stuck with the bigger workload trying to make up for that. That’s a tall order for a smaller muscle that doesn’t have the same long lever/mechanical advantage.
  • That being said, problems in one peroneal mean that you need to look at all three!
  • The video below will show you how to palpate/find this muscle as well as how to stretch it.

#3 Peroneal Tertius

  • Unlike the other two peroneal muscles, the tertius is located IN FRONT of the fibula and lateral malleolus. That means that instead of pointing the toes down, it pulls them up into dorsiflexion.
  • The tertius muscles does however help to evert the foot, making it one of the four muscles that does so.
  • Where the tertius goes, the extensor digitorum longus (EDL) goes! The tertius is technically the lowest portion of the EDL. However, instead of traveling all the way to the toes, it stops and inserts on the top of the fifth metatarsal. On top you have the tertius, and on the side you have the brevis. Then you have the longus tendon wrapping around. That’s a lot of tendon involvement right there! Very easy to jam up the outside of the foot and cause pain/inflammation.
  • As you can see, the areas where this muscle refers pain follow both tendon paths around the lateral malleolus. It’s very easy to mistake this muscle for the other peroneals if you’re going strictly by location.
  • The video below will show you how to palpate/find this muscle and how to stretch to it.

Video #1: How to find and stretch the peroneals


Video #2: Mechanics behind peroneal injuries


Video #3: Treating the peroneals as a group [old case study + treatment video]

Video #4: Crossfriction technique (included peroneal tertius + EDL) using a massage/tennis ball (new)

Sample Treatment Plan:

1) Warm up: this can be with a foam roller, stick or massage ball. 30 seconds each for the peroneal longus, brevis and tertius. Don’t worry about killing yourself here. Easy pressure to flush out the area and get some slack by working in the same direction of the muscle fibers.

2) Main set: cross friction 1 minute per muscle. Break this down into two spots per muscle. If a spot is too tender to work on for 30 seconds? Move the ball up or down slightly. You’re still working the muscle this way without making an area too “hot” too touch.

3) Stretches. 20 seconds x 3 reps. Peroneal longus and brevis can be done together using a belt or strap. Stand up and stretch the tertius/EDL. Twenty second hold per stretch. Give me three of each.

4) The first three steps will help loosen up the peroneals so they can heal. Step four is all about you taking the time to look for the cause.

  • Test your mobility using the foot self eval. Are there restrictions in the toes or ankle? Do your feet point in or out like in the biomechanics video above?
  • Test your knee mobility. Are you able to straighten your knee all the way? Yes means that you can sit on the floor with your legs straight in front of you and press the back of your knee down so that your heel comes up off the ground.
  • Test your hip mobility. With your foot flat and knee straight, how far forward can you move over that foot? Does it look like what I’m doing in the video or do you get stuck?

These are all things you should be thinking about with a peroneal injury instead of focusing strictly on what hurts! I always here athletes talking about their strength routines, not their mobility routines…

Click here to go back to part one on the extrinsics- the shin

Click here to continue to part three on the inside of the lower leg (coming soon)

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