A painful flat foot will often involve a muscle called tibialis posterior. This can be called several names including posterior tibial tendon dysfunction (PTTD) and it can be the result of a sudden change in activity levels, or it could be a gradual increase in discomfort due to increased demand on the muscle. The main purpose of this muscle is to help stabilise the arch of the foot and, more often than not, it happens because the muscle/tendon is not strong enough to cope with the demand that is being placed on it. The picture below shows the area where the muscle sits on the inside of the leg (shown by the red dotted line) while the tendon is shown by the purple line. Its main insertion point is being pointed out, however it has multiple insertions so the pain may spread around the arch of the foot.
You might notice some swelling or pain around the inside of your ankle bone and into the arch of your foot. A reasonably reliable way of telling if this muscle is involved, is to try multiple heel raises on the unaffected leg – and then seeing if you can do the same on the affected leg without any discomfort. An observational study in 2017 set out some values to guide you and the results of this are below. Please remember though that this is just a guide but can be really useful to gauge your ability.
What causes a painful flat foot? 
Spending long periods standing or walking, especially a sudden increase in these activities is often the reason we see problems around this area. Also, if you are overweight, this will increase the stress through the muscle and tendon. Footwear is important, as is the strength and flexibility of certain muscles.
Exercises and information
The videos below will give you advice on how to manage this problem and some exercises that may be useful in strengthening the muscle to help it cope better with the demand that you are placing on it.
There are 7 exercises in total. The video relating to tibialis posterior is number 7 but you may find the others useful too.
Don’t expect things to improve overnight though. It takes time for muscles and joints to adapt and get stronger.
More advanced/progressive loading exercises.
As the initial exercises become easier and less painful, it is important to progress and make the rehabilitation more challenging in order to improve the strength and endurance of the muscle/tendon unit. This progression is vital to ensure that the muscles and tendon are capable of coping with whatever activity you want to return to. Click on the link below for some examples of more advanced exercises. There are 5 exercises in total. Numbers 4 and 5 are the ones that relate more to tibialis posterior.
Please make sure that you are comfortable and ready before making the step up to more challenging rehabilitation, and if in doubt, stay with the current plan until you are.
The leaflets below provide some added information, however, if you feel you would like to talk to a podiatrist about your options, please phone 0141 347 8909 for more advice and support.