In part four of our posts on the intrinsics, we’re going to tackle the muscles on the top of the foot. If you’re someone battling through pain/symptoms on the bottom of your foot then you can guarantee that the little muscles on the top of your foot are involved as well. These muscles are commonly called in when you start compensating for a shortened/altered stride. Instead of getting to relax as the foot and leg swing through following a strong push off from the big toe, these tiny muscles work hard to pull the toes up so that you don’t trip over your own foot.
Before we dig into the muscles, let’s take a quick look at the bones:
This picture is taken standing directly over my foot (lucky you for getting to look at my feet these past few weeks! 🙂 From this view, the lower leg bones (the larger tibia bone on the inside and the skinny fibula on the outside) are stacked directly on top of the talus which is then stacked directly on top of the calcaneus (heel bone). That’s why the tibia and fibula have lines through them. They will effectively block the view of calcaneus and most of the talus. So… even though you can see the calcaneus labeled in the picture above, understand that it is not on the surface of the top of the foot. It is deep below more superficial structures.
The top of the foot features a combination of long tendons coming from muscles above the ankle (aka the extrinsic muscles of the foot), as well as, the small intrinsic muscles themselves. There are three muscles on the top of the foot: 1) the dorsal interossei, 2) the extensor hallicus brevis and 3) the extensor digitorum brevis.
#1 Dorsal Interossei (DI)
- There are actually four little muscles that make up the DI. They originate along the metatarsal bones and attach on either side of the proximal phalanx of toes 2, 3, and 4 (the big toe is number 1 and the little toe is number 5).
- In the picture above you can see that the tendons attach to the funky looking white diamond. That diamond shape is the extensor mechanism and is responsible for pulling the toes back into extension. The long extensor digitorum tendon runs through the middle, on top of the foot intrinsics. I only included part of it in the picture above to better show the DI.
- These muscles are responsible for several movements. The first is that they abduct (pull apart) and flex toes 2-4 at the MTP joint. Remember- this is the joint between the long metarsal bone and the first phalange, not the tiny little toe joints themselves. The second movement is to extend the toes at the furthest interphalangeal joints via the extensor mechanism.
- The important thing here is to realize that these little muscles are tied to a muscle above the ankle (aka the EDL- extensor digitorum longus). That means restrictions either in the DI or the EDL will impact each other.
- The common pain referral areas for this muscle are the two purple circles pictured above. Note: these areas are also present on the bottom of the foot.
- In the last post we talked about the plantar interossei. They are directly below the DI in the exact same inter-metatarsal spaces. Problems in one will definitely be present in the other. This is why they share the same pain referral areas.
- Mobility restrictions/trigger points in these little muscles are commonly misdiagnosed as suspected stress fractures, nerve entrapments, and tarsal joint dysfunction.
- In the video below, we’ll go over finding the DI muscles/palpating them, as well as, how to stretch them.
#2 + 3 The Extensor Digitorum Brevis (EDB) and the Extensor Hallicus Brevis (EHB)
- As the caption above says, I’m combining these two muscles because they share a common origin. The difference between them is that ones goes strictly to the big toe and one goes to toes 2-4. As a general rule of thumb, any muscle with the word “hallicus” in the title means big toe. Any muscle with the word “digitorum” in the title means digits/toes.
- Both of these muscles originate from the top of the calcaneus and move down the top of the foot to insert onto the lateral side of the proximal phalanx for toes 1-4. The EHB goes alone to the big toe while the EDB tendons attach to the overlying EDL tendons via the extensor mechanism.
- Again, this is important. That means the EDB are also attached to a muscle above the ankle (an extrinsic muscle). That means that restrictions in one will affect the other and vice versa.
- The common pain referral area for this muscle is the big purple circle pictured above.
- Mobility restrictions/trigger points in this area are commonly misdiagnosed as suspected metatarsal stress fractures and nerve entrapments.
- In the video below, we’ll go over finding the muscles/palpating them, as well as, how to stretch them to test their mobility.
Video – Palpation (aka how to find the muscles in your foot) and Stretching
Over the past few posts we’ve spent a lot of time talking about the extrinsic muscles and what their tendons in the foot attach to. In the next post we’re going to tackle the extrinsic muscles themselves. From there we’re going to talk treatment and what other areas you should be thinking about when symptoms/injuries arise.
Click here to continue on to the extrinsic muscles (coming soon)