Pronation is the natural rolling motion of the foot while walking or running. The degree of pronation varies for everyone. Underpronation, also known as supination, is a condition where the degree of pronation causes the foot to turn inward, creating a tendency to walk on the outside edge of the foot.
Underpronation is either an inherited biological defect or a congenital defect, caused by the feet lying cramped or twisted while in the uterus. The muscles, tendons, ligaments and other soft tissues in the foot become rigid to adopt the misalignment of the foot, causing the ankle bone to turn inward and pulling the arch of the foot upward.
An underpronating foot appears to roll outwards when walking or running. The Achilles tendon seems to slope inward and the ankle bone will appear prominent. Supinators also have a condition called Pes Cavus, which means that the arch of the foot is very high Callouses, bunions and hard skin on the outside of the foot are another sign of underpronation, and because of uneven weight distribution, there may be tightness in the ankles and calves, creating a bow-legged appearance.
Underpormation can cause sore feet, legs and knees. Because of the extra strain put on muscles that twist and shift to accommodate underpronation, there may be ankle instability. This causes frequent sprains and tight Achilles tendons. The overall tightness leads to diminished foot mobility and an increased possibility of injury. Knee pain and ankle pain are also associated with supination, as are shin splints, hip pain and sometimes pain in the lower back.
To minimise the possibility of injury, it's advisable to do a proper warm-up before exercising. Stretching and conditioning exercises targeted at the lower leg and foot will help prevent injuries as will good, well cushioned and well-fitting shoes. It's important to have proper measurements taken of foot length, width and depth and to wear appropriate socks when being fitted. A podiatrist can analyse gait and advise on proper support or even prescribe orthotics which can help counter supination problems.