What is Pronation and Supination?
Your feet each have about 30 bones and joints. These bones and joints work together to make your foot so that it can both adapt to the ground surface, and propel your body forward during walking or running.
Pronation and Supination refer to motion in the joint under the ankle, called the Subtalar Joint. This joint is like a key that locks and unlocks the other joints of your foot.
When the joint pronates, the foot unlocks and the other joints become loose and allow your foot to adapt its shape to match the ground surface. A pronated foot often has a flattened or low arch.
When the foot supinates, these same joints lock up and your foot becomes rigid, allowing you to propel yourself forward. A supinated foot often has a high arch.
Is Pronation normal?
During walking or running, your foot pronates and supinates with each step. The foot pronates when your heel hits the ground, and begins to supinate as the ball of the foot hits the ground. The foot should be fully supinated as your toes push off the ground.
Pronation is a normal and necessary motion of the Subtalar Joint. Pronation becomes a problem only when the foot is in a pronated position at a time when it should be supinated for propulsion.
How much Pronation during walking or running is too much?
The foot is over-pronated if the foot remains pronated as weight shifts from the heel to the ball of your foot.
What causes Over-Pronation?
Over-pronation is usually related to the bone structure of your feet and specifically of the Sub-Talar Joint. Bone structure is inherited. Other factors that can influence Over-Pronation include:
- Leg-length difference
- Hypermobility of joints (double-jointed)
- Tight calf muscles
Will Over-Pronation cause problems with my feet?
Your foot is a bony structure that is supported by muscles, ligaments, and tendons. The bones should be carrying the force of body weight as you walk. A normal Pronation-Supination cycle allows smooth transfer of body-weight and ground force from the heel bone, though the bones of the midfoot and to the bones of the ball of the foot and toes with each step.
When the foot over-pronates, much of these forces get transferred through the supporting mucles, ligmant and tendons. Eventually these structures become fatigued and problems such as plantar fasciitis, tendonitis, shin splints, or joint pains start to set in. Abnormal pull of tendons over time can cause deformities such as bunions and hammer toes. Too much movement through midfoot joints can cause bone spurring. The ligaments and soft tissue supports around the subtalar joint itself can also become painful, a condition known as Sinus Tarsi Syndrome.
The over-pronated foot also contributes to alignment problems in the knees, hips, and low back. Problems such as Runner's Knee (Patellofemoral Syndrome or Chondromalacia) and Iliotibial Band Syndrome (lateral knee pain) are often related to Over-Pronation.
How is Over-Pronation treated?
Over-Pronation is treatable. The simplest treatments are usually best, and include stretching the calf muscles and wearing supportive footwear. Exercises to strengthen leg and foot muscles may also help.
Some patients may need an in-shoe foot orthotic device to add extra stability and better control the Subtalar Joint motion.
Occasionally a patient with Over-Pronation will have symptoms of pain and difficulty walking that are not responsive to simple treatments. These patients may require surgery to correct the Over-Pronation by changing the anatomy of the foot to better control Subtalar Joint motion.