Inside ankle pain when you run: the tendon that holds your arch up

The pain is hard to point to. It sits somewhere behind the bump on the inside of your ankle, and when you try to describe it you end up drawing a curve with your finger that ends inside the arch.

That curve is the shape of one tendon, and it is the reason this gets called everything from a sprain to plantar fasciitis before anyone names it.

Where it runs

The tibialis posterior comes down the deep back of the calf, passes behind the bump on the inside of your ankle, turns underneath it, and attaches inside the arch. That hook is why the pain travels.

1. 1Behind and under the bump on the inside of the ankle
2. 2Where the tendon attaches, inside the arch

Its job is to hold the inside of the arch up while you are on one leg, which is every moment of a run. It is the main dynamic support of the medial arch, and when it stops coping, the arch flattens¹.

The test you can do at home

Stand next to a wall, put one finger on it for balance, and do a slow single-leg heel raise. Then do the same on the other side and count.

Two things tell you something. Whether it reproduces the pain, and whether you can do meaningfully fewer on the sore side.

Those medians are for the general population and a runner should be well above them. The number that matters here is the difference between your two legs, because that is what you can act on.

The tendonBone

Shape of the sore area

The tendonA curve, from behind the ankle bone into the arch.

BoneOne small point you can cover with a fingertip.

First steps in the morning

The tendonStiff, then eases within minutes.

BoneFine on waking, worse the longer you are up.

Heel raise

The tendonSore, and fewer than the other side.

BoneSharp at one spot, and you stop.

Over a run

The tendonOften warms up, then returns late.

BoneComes on earlier each run.

Pain lower down the inside edge of the shin bone, spread over several centimetres, is a different problem. That one is the bone.

Why the insole earns its place here

We are usually cautious about insoles. This is the exception, and the reason is mechanical: the tendon is trying to hold the arch up, and an arch support does part of that job while the tendon gets its capacity back.

What the exercise trials found

Two randomised trials tested adding exercise on top of orthoses, and they did not fully agree.

Read together, they say something useful. Everyone got better, the orthosis was doing real work in every arm, and loading the tendon probably helps but is not the whole story. It is also worth knowing where these findings stop. The participants were adults with a flattening arch, most of them older than the average runner, and none of the trials were run in a running population.

Running while you rebuild it

Tendon problems on the inside of the ankle respond badly to being ignored and badly to complete rest. The middle is where this gets better.

How long it takes

The trials ran for 12 weeks and improvement was still happening at the end of them. That is a reasonable expectation for this tendon: measurable progress within a few weeks, and the useful part of the recovery spread over about three months.

Running injuries on the inside of the foot and ankle are a meaningful share of what runners get⁶, and this one has a habit of being managed for months as something else before it is named.

When to get it looked at

A tendon that is losing the ability to hold the arch is worth catching early, because the later stages are managed differently and surgery enters the conversation after three to six months without progress¹.