Sinus Tarsi Syndrome: Ankle Pain That Lingers After a Sprain

Here's a story I hear all the time in the office: you rolled your ankle months ago — on a trail near Fallbrook, stepping off a curb, coming down wrong on a pickleball court. The swelling went away. The bruise faded. But there's still a nagging ache on the outside of your ankle, just in front of the ankle bone, and the ground never feels quite trustworthy anymore. Uneven surfaces make you nervous. That pattern has a name: sinus tarsi syndrome.

What Is the Sinus Tarsi?

The sinus tarsi is a small tunnel on the outside of your foot, just below and in front of the outer ankle bone, between the ankle bone and the heel bone. It's packed with ligaments, small blood vessels, and nerve endings that help your brain sense where your foot is in space. When that tunnel gets inflamed or scarred — most often after an ankle sprain that stretched the tissues inside it — it can keep hurting long after the original injury seems healed.

According to a 2020 review in Foot and Ankle Surgery, the condition typically shows up as two things together: pain in that specific spot, and a feeling of instability, especially on uneven ground. A 2023 review in the Journal of Clinical Medicine makes another point worth knowing — "sinus tarsi syndrome" is really an umbrella term, and several different problems can hide underneath it, from lingering inflammation to instability of the joint below the ankle. That's why a careful exam matters more than a quick label.

The Telltale Signs

Patients with sinus tarsi syndrome usually describe some mix of the following: a deep ache or sharp pinch on the outside of the foot just in front of the ankle bone, pain that's worse on uneven ground, grass, sand, or trails, a sense that the ankle might give way even though it never fully does, stiffness in the morning that loosens with movement, and tenderness when you press directly on that little hollow in front of the outer ankle bone. Walking on flat pavement often feels fine. It's the hiking trail, the gravel driveway, or the sloped yard that brings it out.

Why It Happens

The most common trigger is an inversion ankle sprain — the classic roll where the sole of your foot turns inward. The ligaments inside the sinus tarsi get stretched or torn along with the better-known ankle ligaments, and while the outside of the ankle heals, the tissue inside the tunnel can stay inflamed or scar down. People with flatter feet can also develop it without a sprain, because a foot that rolls inward too much compresses the sinus tarsi with every step.

How We Diagnose It

Diagnosis starts with your story and a hands-on exam — pressing on the sinus tarsi reproduces the pain in a way that's hard to mistake. X-rays help rule out other causes like arthritis or an old fracture. In some cases, a diagnostic injection into the sinus tarsi does double duty: if numbing that one small space takes the pain away, we've confirmed where the problem lives, and the anti-inflammatory medication in the injection often starts the healing at the same time.

Treatment: Calm It Down, Then Build It Back

The good news is that most cases respond to conservative care. The plan usually looks like this:

Settle the inflammation. Activity modification, ice, and anti-inflammatory strategies give the irritated tissue a chance to quiet down. For stubborn inflammation, a targeted injection into the sinus tarsi can make a real difference.

Control the motion. If your foot rolls inward too much, every step re-compresses the tunnel. Custom orthotics built from an impression of your feet can hold the heel in a better position and take the pressure off — this is one of the conditions where orthotics genuinely earn their keep. Taping or a lace-up ankle brace helps during the transition.

Rebuild the stability. The nerve endings in the sinus tarsi are part of your balance system, and after a sprain they need retraining. Our sinus tarsi exercise guide walks through the balance and strengthening work step by step, and pairs well with our ankle strengthening program.

For chronic cases that don't settle with the basics, we talk through additional options in the office, including regenerative injection therapy for some patients, and imaging to look for an underlying problem the exam can't see. A small number of stubborn cases end up needing surgical evaluation — but that's the exception, not the rule.

The Bottom Line

If the outside of your ankle still aches months after a sprain and uneven ground makes you hesitate, sinus tarsi syndrome belongs on the list of suspects. A focused exam can usually sort it out in one visit, and most people improve with a combination of calming the inflammation, supporting the foot, and rebuilding balance. If this sounds like your ankle, we're happy to take a look — and if you're recovering from a recent sprain, our sports injury care page covers what early treatment should look like.