Over-pronated / Hyperpronated feet
This is a very common term that is used to describe a flexible/dynamic, misaligned foot structure. Many people know the term yet very few actually know what specifically causes a foot to become over-pronated.
What is an over-pronating/pronated foot?
Pronation is a mechanical term used to describe specific motions that occur as a result of ankle bone motion on the heel bone. When the ankle bone is pronating, it is turning slightly inward, downward, and forward. The opposite of pronation is supination when the ankle bone moves slightly outward, upward, and backward. There should be 2/3 supination motion and only 1/3 of pronation motion between the ankle and heel bones. The reason why there should be more supination motion is that supination strengthens the joints within the feet. Pronation weakens the joints of the feet. It is more important for the joints to be mainly strengthened than weakened.
There is an important reason why the joints in our feet have some flexibility. The ground that we walk on is not always flat. Pronation allows our feet to adapt to those uneven surfaces.
Now that we know how the mechanics of the foot should be working, we can now find out what the walking cycle looks like when the ankle bone partially dislocates on the heel and arch bone leading to a longer duration of the ankle bone in the pronated position.
The ankle bone will continue to be in that pronated position into the midway portion of full foot contact. The actual length of the time that the ankle bone is abnormally in the pronated position depends on the amount of dislocation of the ankle bone. A second complicating factor is whether the supporting ligaments are healthy or have they also become diseased due to the years of walking on that over-pronating foot. Eventually, the amount of excessive pronation will be further prolonged with the supporting tendons getting overstretched. This is all further complicated because of continued walking. The final stage is when the joints become diseased and unstable. This is the reason why early treatment of over-pronation with an effective option should be accepted.
The graphic shows that the ankle bone is pronating causing the joints of the foot to be in a weakened rather than a strengthened state.
The ligaments are going to be strained, a thick tissue on the bottom of the foot, plantar fascia, will be strained, and a strong tendon to the inner arch will also be strained. Eventually there will be a complete collapse of the foot and loss of joint stability.
What causes a foot to over-pronate?
The ankle bone partially dislocates during standing, walking, or running. The ankle bone loses its stability and is in a pronated position longer than it should be. There is a second component that occurs between the small bone in front of the arch bone and long first metatarsal bone. Instability at the joint can cause excessive forefoot pronation. An over-pronating foot begins with the instability of the ankle bone and can be further complicated with the instability of the base of the first metatarsal bone.
It is worth noting that some authors have claimed that over-pronation is due to a ligament disease or that it is a worn-out, over-stretched tendon. Those tissue diseases can be present in an over-pronating foot, but not always. The partial dislocation of the ankle bone will over-stretch the ligaments and tendons. The partial ankle bone dislocation is always present before the ligaments and tendon over-stretching. Many times, surgeons have attempted to repair the damaged ligaments or tendons without addressing the ankle bone instability. The repair seemed to do-the-job at first, but after a while of the excessive ankle bone motion pushing on the bones and joints, that repair became compromised and ultimately failed.
Why is an over-pronating foot a “bad” thing?
Parts of the foot that are strained/damaged because of an over-pronating foot:
- Spring ligament – calcaneal-navicular ligament
- Growth plate on the back of the heel bone
- Plantar fascia
- Posterior tibial tendon
- First metatarsal bone – at the base where it attaches to the arch bone
- Big toe joint
- Ball of the foot – metatarsalgia
- Toes – develop hammertoes
Then up towards the body:
- Nerve behind the inner ankle bone
- Achilles tendon/calf muscles
- Ankle bone