Posterior Tibialis Exercises: All About This Muscle

Tight calves and shin splints are common issues runners face. But they shouldn’t be the only areas you pay attention to in your lower legs. If you’re ignoring a small stabilizing muscle called the posterior tibialis—which plays an important role in your running and walking mechanics—you might end up in pain, particularly if it’s weak and overused.

“The posterior tibialis is a muscle that originates on the back, or posterior, part of the tibia and fibula (your lower leg bones), up close to your knee,” explains Cathlin Fitzgerald, D.P.T, C.S.C.S., senior physical therapist at Custom Performance in New York City. It attaches to a few different areas of your bones via tendon, she says: two midfoot bones (called the cuneiform and the navicular bone, which is right at your arch), plus the base of your second, third, and fourth toes.

Here’s what you need to know about how this tiny muscle supports your foot and helps make you a better runner, plus five moves to strengthen it.

How Your Posterior Tibialis Aids Your Running

“The function of the posterior tibialis muscle is to plantar flex [toes away from shin/pointed toes] and invert the ankle [move inward toward midline], and it also plays a key role in stabilizing the medial longitudinal arch as the foot hits the ground,” says Brian Gurney, D.P.T., C.S.C.S., a trainer, board-certified sports clinical specialist, and physical therapist at BeFit Therapy in NYC. “If the muscle is not functioning properly, a runner will present with a flat foot or compressed arch appearance.”

That reaction can lead to pain underfoot from the repetitive motion of running if you don’t strengthen it.

It’s worth noting that all runners, not only those with flat feet, can have a weak posterior tibialis—though it can contribute to flat feet, says Fitzgerald.

The plantarflexion and inversion motions along with arch stabilization are all crucial for more efficient and powerful running form, notes Fitzgerald. “Plantar flexors power the push-off aspect of the gait cycle,” she says. Additionally, “the support of the arch is necessary for proper foot function to transfer forces while running.”

How to Tell Your Posterior Tibialis Needs to Get Stronger

You might not notice your arch collapsing by yourself—so the best way to check out your posterior tibialis strength is to see a physical therapist. Gurney takes clients through a general squat test and watches from both the front and the back to see how the ankle is stabilizing through the range of motion. “If the muscle is weak, I’ll see the arch flatten and the toes kick out to the side,” he says.

Another simple way to assess the muscle is to stand on one leg in front of a wall, touching it lightly, and press up onto your toes to lift your heel off the ground. “If there is a dysfunction of the muscle, it will be difficult to complete 10 full repetitions,” notes Gurney. “Something I look for is the fatigue factor—whether the heel is coming up as high with each rep.”

Besides having a PT evaluate your form, the number-one sign of weakness in this muscle that you might notice on your own is pain, typically worst in the morning or when getting up from sitting for a long duration.

“This pain often gets mixed up with plantar fasciitis,” says Fitzgerald. “A key difference between post tib foot pain and plantar fasciitis is where the pain is located: Plantar fasciitis is more typically felt in the heel whereas post tib pain is right in midfoot along the arch—right where it connects to the navicular bone [in the middle of the foot]—and not at all in the heel.” You might feel the ache on the inside of the lower leg as well, she adds.

Repeat. Do 3 sets of 15 to 20 reps stretching shouldn’t be a part of the game plan, says Fitzgerald. “I would argue that the focus should be nearly completely on strengthening and mechanics,” she says. “Often a muscle that is weak will give the sensation of tightness—plus, this is usually a tendon injury, and we don't want to focus on stretching a tendon injury.”

By tendon injury, she means tendinitis, and posterior tibialis tendinitis can sometimes be mistaken for Achilles tendinitis. “Tendinitis occurs when a tendon is overloaded, and muscle weakness is a contributing factor to that overloading,” Fitzgerald explains.

What You Likely Don’t Need to Worry About

An issue called posterior tibial tendon insufficiency is a condition that commonly comes up when you google the posterior tibialis muscle, but it’s rarely what’s happening with runners, says Fitzgerald.

“This condition is more serious and debilitating than the typical tendon problems we see for runners—it often includes developing a foot deformity and recommendations for surgery,” she says, noting that runners often come to her panicked about it. “I’m here to alleviate some of that fear: I see a lot of posterior tibialis tendon issues and have not once seen post tib insufficiency in 10 years of specializing in runners.”

5 Exercises to Target the Posterior Tibialis

Even if you don’t have flat feet, all runners can benefit from working this muscle. Fitzgerald and Gurney recommend these exercises to strengthen it and give your running some extra support. While they’ll all help strengthen your posterior tibialis, Gurney says to keep in mind that it’s not the only muscle they’ll fire up. “All of the exercises will impact multiple muscles; there is nothing that only targets the posterior tib,” he notes.

1. Seated Banded Ankle Isometric Hold

posterior tibialis exercises, seated iso ankle hold

thomas hengge

Repeat. Do 3 sets of 15 to 20 reps: “This is a basic exercise that targets the movements the post tib performs,” says Fitzgerald.