An introduction to foot pronation and supination
The foot is comprised of 26 bones and is often overlooked when dealing with physical dysfunction further up the body. Proper foot mechanics are essential to avoiding dysfunction in both the area of the foot, and further up the kinetic chain.
In this article I'll be looking at pronation and supination of the foot, specifically as it refers to an excess of these positions which lead to dysfunction. Note that I am not talking about the foot moving into these positions temporarily as we walk or run, but rather the foot being stuck in one of these two positions.
Have you ever taken a look at the way the soles of your shoes wear out? Do you see the outside wearing quicker than the inside? Or perhaps you've noticed that one side of the heel wears much quicker than the other areas? This gives good information about how a person strikes the ground when they walk or run. I remember as a kid my shoes were always well worn on the outside edge. Ideally, the soles would wear away in a fairly even fashion, but that doesn't happen as often as we'd like.
Before looking at what supination and pronation actually mean and what effects they have, let's take some time to look at some basic anatomy of the foot.
As mentioned above the foot is comprised of 26 bones, along with all the joints formed from the articulations of these bones. We can view the foot in two sections. The hind foot which comprises the Calcaneus (heel bone), Talus, and the tarsal bones. The tarsal bones are comprised of the navicular medially, the cuneiform bones (medial, middle, and lateral), and the cuboid bone is found most laterally.
The second section is the forefoot which is made up of the metatarsals, and the proximal, middle, and distal phalanges (basically your toes).
These bones articulate with each other to form a large number of joints in the foot. The talus bone of the hindfoot also articulates with both the malleoli of the tibia and fibula of the leg to form the ankle joint.
Arches of the foot
The foot has three arches (shown below) that help to ensure proper foot mechanics. These are the medial arch, the lateral arch, and the transverse arch. The first two of these are of primary importance when talking about foot pronation and supination.
These arches are maintained by muscles attaching to the underside of the foot. A loss of tone in these muscles causes the arches to drop down and can eventually result in flat feet, or a heavily pronated or supinated foot position.
On the medial side the Tibialis Posterior muscle holds up the medial arch, and the lateral arch is maintained by the Peroneal muscles. Let's take a look at what a fallen arch on the medial side, resulting in excessive pronation, looks like from the posterior view.
We can imagine as the foot moves further into a pronated position, the muscles on the medial side of the leg have lost tone and are lengthened. In addtion this position will cause a large amount of stress to the ankle joint and the tendon of the calcaneus (achilles tendon) when it is placed under load. Not only is the ankle joint an obvious load bearing joint, it also (along with the foot) bears the load of the entire body. Forces that are placed through this joint when running for example, will now not be applied evenly through the ankle or indeed further up the kinetic chain.
Everything is connected. Let's quickly imagine the problems such a foot position could cause.
1. The medial arch drops causing pronation and a change in ankle position.
2. The ankle joint is formed by the connection of the bones of the lower leg to the talus. This means the position of the tibia and fibula are altered.
3. The proximal part of the tibia forms the distal portion of the knee joint. A shift or rotation of the tibia is going to cause the knee to be misaligned. Very often a dropping inwards of the knee (valgus movement).
4. This change in knee position can cause compensation further up in the hip joint, as pronation usually results in the femoral head externally rotating and pushing against the front of the hip socket (acetabulum).
5. This external rotation of the hip can lead to an unlevelling of the sacrum in the low back.
6. The pronated foot position also causes a relaxing of the gluteus maximus muscle leading to misfiring or not firing at all.
You get the picture right? One thing in the chain becomes dysfunctional and the whole chain is going to be affected.
It gets even worse when force is applied through this chain. Things like knee cartilage and the hip joint suffer unnatural wear and tear, leading to pain, reduced mobility, and often times surgery.
Supination is the dropping of the lateral arch of the foot and can be viewed as the opposite of pronation.
As before this position will result is dysfunction up the kinetic chain of the body if not corrected. As you would expect the results of a supinated foot position lead to many of the opposite compensations of pronation. In this scenario the tibia is more prone to externally rotating with varus movement of the knee (bow legs), and the hip joint now internally rotates with the femoral head pressing against the back of the acetabulum. Gluteus maximus is now being recruited excessively leading to chronic tightness and dysfunction in the hip and lower back region.
The stirrup spring system
This system refers to a system of muscles and fascia that help to transfer energy correctly through the lower leg and maintain proper foot mechanics. As seen in the image below, the system is comprised mainly of three muscles. These are peroneous longus, tibialis anterior, and biceps femoris (a hamstring muscle). I also think you can include tibialis posterior in this group.
Collectively these muscles help to maintain the arches of the foot. By attaching to the underside of the foot, these muscles effectively form a kind of 'stirrup' which holds up the arches. As mentioned earlier, a loss of tone in these muscles cause the arches to drop and can lead to pronation and supination. When walking or running, this system helps energy transfer through the foot and up the leg. Dysfunction in the foot will lead to a reduction in effective energy transfer via this system.
Many times people are prescribed orthotics which are inserted into the shoes in order to artificially lift the foot and provide support. Over time these can be reduced if the foot starts to return to a normal position, but this doesn't always happen.
Sports massage and MAT work can help to restore the foot to normal function, along with consistent homecare exercises to work relevant muscles and improve mobility. It's always worth checking with a qualified therapist on your foot position. This is especially true if you are a regular exerciser or runner, as constant forces through joints that are misaligned wil inevitably lead to pain and loss of function in the area.
Thanks for reading,