The flexor hallucis longus and flexor digitorum longus are part of the muscular team that allow us to walk. These muscles in particular help bend the toes so that, as we walk, we can push off of the ground. This push helps propel us forward and is an essential component of proper gait.
These two deep muscles are crucial for proper alignment in the foot and stability and control at the ankle. Personally, I believe that our bodies are a structure that is built from the base up. This means that the flexor hallucis longus and flexor digitorum longus are as important for our feet and ankles as they are for our entire body.
Where are the flexor hallucis longus and flexor digitorum longus located?
The origin of the flexor hallucis longus is on the lower two-thirds of the posterior surface of the fibula and on the interosseous membrane. I don’t think we’ve talked about the interosseous membrane in previous posts.
There is an interosseous membrane present in the forearm and in the lower leg. The interosseous membrane in the lower leg runs between the tibia and fibula. It stabilizes the bones and also helps serve as a division line, separating the front half of the leg from the back half. This helps make sure that muscles don’t cross the line and end up on the wrong side of the body.
The origin of the flexor digitorum longus is on the medial part of the posterior surface of the tibia. This means that this muscle originates on the inside, posterior surface of the tibia.
The flexor hallucis longus inserts on the plantar (bottom) surface of the distal phalanx of big toe. This means that it inserts on the bottom of the tip of your big toe.
As the flexor digitorum longus moves toward its points of insertion, it divides into 4 tendons. These insert on the plantar (bottom) surfaces of the bases of the distal phalanges of the second through fifth toes. Essentially, the flexor digitorum longus inserts on the bottom of the tips of your second through fifth toes.
What do the flexor hallucis longus and flexor digitorum longus do?
The main functions of the flexor hallucis longus and flexor digitorum longus are to flex the toes. Naturally, the flexor hallucis longus flexes the big toe, and the flexor digitorum longus flexes the other four toes. Because of toe flexion, we are able to push off the ground when we are walking. Plus, when all the toes bend, it creates a grip of sorts on the surface beneath your toes. This aids in stability throughout your body.
These muscles also work together to help plantar flex the ankle joint and invert the foot. When you point your toes, that is plantar flexion. It’s actually a movement that comes more from your ankle than from your toes, but I suggest you not correct your instructor if you are ever told to point your toes.
Inversion of the foot is when your arches lift from the ground, allowing the soles of your feet to face each other. It may also feel like you have more weight distributed to the outside edges of your feet than to center.
The flexor hallucis longus also helps stabilize the inside of the ankle.
What happens when they don’t work correctly?
When the flexor hallucis longus and flexor digitorum longus become shortened, hammer toe deformities may occur. Any of your toes may get hammer toe. If you have hammer toe, your middle toe joint will be bent, sticking up into the air. To me, it looks like your toes are ready to play piano.
This may not sound like such a big deal, but if you note that most shoes have a finite amount of space in the toe box, a little bit of a hammer toe can become incredibly painful in a short amount of time.
How to Relieve Flexor Hallucis Longus and Flexor Digitorum Longus Tightness and Weakness Yourself
In any cases of pain, it is always best to see your doctor. Your doctor can order the appropriate imaging, medication, and therapy to help determine the best way to restore your health.
However, if you’re in the early stages of pain and you want to try to do something about it yourself, here are my recommendations. Oddly, I have found that weakness = tightness. This means that you will have to do a combination of exercises specifically triggering the use of the flexor hallucis longus and flexor digitorum longus mixed with the exact opposite movements.
Practice raising up to your tip toes several times. Then, use the floor to help you turn your toes the opposite way. Make sure to get a good stretch along the top of each toe and at the base of the toe joint.
You can also practice strongly pointing and flexing your foot at the ankle. This combination of plantar flexion and dorsiflexion should help strengthen and stretch these muscles.
Also, you can practice moving from an inverted foot position to neutral. Then, from neutral to everted. To evert your foot, let your weight press into your arches. Smoothly roll from one position to the other, always making sure that you stop in a perfect neutral position.
I consulted The Concise Book of Muscles by Chris Jarmey. Recently, the book was revised and is in its third edition.
Also, I consulted my Flash Anatomy Muscles Flash Cards. If you really enjoy anatomy and want a tool to help you locate specific muscles correctly, I highly recommend these flash cards. I turn to them any time a client comes in with pain.
The link above is a link to buy them on Amazon. If you purchase them from this link, I earn a small commission.
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