by Bob Longworth MSc DPodM

At Podiatry Clinics (Yorkshire) Ltd we have a reputation for getting patients better when other treatments for lower limb problems have failed. Understanding the biomechanics of the foot and knowing when muscles fire in the gait cycle are essential tools for getting the right treatment in place. There was an interesting case this week that brought this to light……..

Illustration: Freddie Wood Jones from his wonderful book ‘The Foot’ (1944)

There is a tendon on the inside of the ankle that comes from the ‘Tibialis Posterior’ muscle (so called because it attaches to the back of the tibia). It can often cause problems with tendonitis/ tendinopathy/ dysfunction in feet that are ‘Pronating’ more than is good for them. The terms ‘Pronation’ and its opposite ‘Supination’ are great at describing hand movements but not great terms for how the foot moves (see here for an in-depth discussion about it) but they are ingrained in the literature so we’re stuck with them.

If you stand and twist your hips in one direction, the foot on the leg that is internally rotating will pronate (go flatter) and the foot on the leg that is externally rotating will supinate (arch goes higher). You can see how pronating the foot might cause tissues that support the inside of the ankle to become stressed more. Stand up and try it yourself.

Twisting hips to the right makes the left leg internally rotate and Pronate the left foot.

One of the things that can really help Tib Post Tendinopathy is to reduce the amount of foot Pronation with a sturdy shoe or with an insole that supports the inner foot. It was interesting therefore to see a patient this week who had been prescribed a pair of £450 insoles to reduce foot Pronation, which subsequently caused a tear within a previously asymptomatic Tibialis Posterior Tendon. The prescriber had asked the patient to break the insoles in slowly but when they reported the new pain, the practitioner was at a loss to help. So how could an ‘anti-pronatory’ insole cause problems with a tibialis posterior tendon?

Well…..let’s look at how Tibialis Posterior works. It fires twice in the gait cycle, once to control/slow down the rate at which the arch decreases in ‘midstance’ and then again to raise the arch as the heel lifts from the ground in ‘terminal stance’.

Taken from Murley et al (2014)

The insoles this patient had been given had quite a high arch support and would stop pronation during midstance (so far, so good). Unfortunately, the insole had been cut away from under the big toe area (known as a 1st ray cut out). This is a fashionable insole adaptation amongst Podiatrists and a good thing to do to help alleviate big toe pain (as told in this well written paper by friends of ours).

In this case unfortunately, it meant that as the patient’s heel came off the ground, the foot was forced into pronation as there was no insole material under the inside of the forefoot but there was material under the outside. This caused the patients foot to greatly pronate as the heel lifted, putting much more load on the Tibialis Posterior tendon during its 2nd peak. The insole was catapulting the foot in one direction whilst the tendon was trying to do the opposite, resulting in injury.

When the patient complained about the new pain she was just advised to persevere with them. Thankfully she didn’t and is now on the mend.

When it comes to insole therapy (or ‘foot orthoses’ as they are often called) it’s not about how much they cost, it’s about where you apply the force to foot. We use different types that we adapt in clinic that cost between £40-£80 depending on the type used. We prefer to be cheap and cheerful as most of the time, these insoles are not needed long term, just long enough to get you over your problem then back to how you were.

The type of insole we often use and adapt

Insoles, Exercises, Joint Mobilisations, Fascial Manipulation and steroid injections are all tools we can offer to help reduce your musculoskeletal symptoms.

by Bob Longworth MSc DPodM