Over Pronation (Flat Feet) refers to the biomechanical shock-absorbing motion of the ankle, foot and lower leg. It is the natural inward flexing motion of the lower leg and ankle. Standing, walking, and running cause the ankle joint to pronate which in turn helps the body to absorb shock and allows it to control balance. An ankle joint that is too flexible causes more pronation than desired. This common condition is called Over- Pronation (sometimes referred to as "Flat Feet"). This foot condition places an extreme degree of strain on various connective tissues of the ankle, foot, and knee. If this condition is not addressed foot pain and toe deformities such as bunions and hammer toes (just to name a couple) may develop. Hip and lower back pain may also be residual results from this condition.
There is a relationship between biomechanics and injury that is specific to each body part. Overall though, poor mechanics will either increase the landing forces acting on the body or increase the work to be done by the muscles. Both increase the stress, which, depending on the individual and the amount of running can become excessive and cause injury.
Because pronation is a twisting of the foot, all of the muscles and tendons which run from the leg and ankle into the foot will be twisted. In over-pronation, resulting laxity of the soft tissue structures of the foot and loosened joints cause the bones of the feet shift. When this occurs, the muscles which attach to these bones must also shift, or twist, in order to attach to these bones. The strongest and most important muscles that attach to our foot bones come from our lower leg. So, as these muscles course down the leg and across the ankle, they must twist to maintain their proper attachments in the foot. Injuries due to poor biomechanics and twisting of these muscles due to over-pronation include: shin splints, Achilles Tendonitis, generalized tendonitis, fatigue, muscle aches and pains, cramps, ankle sprains, and loss of muscular efficiency (reducing walking and running speed and endurance). Foot problems due to over-pronation include: bunions, heel spurs, plantar fasciitis, fallen and painful arches, hammer toes, and calluses.
You can test for pronation by looking at the leg and foot from the back. Normally you can see the Achilles Tendon run straight down the leg into the heel. If the foot is pronated, the tendon will run straight down the leg, but when it lies on the heel it will twist outward. This makes the inner ankle bone much more prominent than the outer ankle bone.
Non Surgical Treatment
Over-pronation and the problems that go with it are treated with shoe inserts called arch supports or orthotics. You can buy orthotics at a pharmacy or athletic shoe store or they can be custom made. Make sure the arch supports are firm. If you can easily bend them in half, they may be too flexible.
Subtalar Arthroereisis. The ankle and hindfoot bones/midfoot bones around the joint are fused, locking the bones in place and preventing all joint motion. This may also be done in combination with fusion at other joints. This is a very aggressive option usually reserved for extreme cases where no joint flexibility is present and/or the patient has severe arthritic changes in the joint.