Pronation and supination refer to the natural movements of the foot and ankle, which influence gait mechanics and overall foot health. These movements primarily involve the subtalar joint but also impact the forefoot. Considerations for pronation and supination of the rearfoot and midfoot have been previously reviewed. This post will review the forefoot considerations, which are the most comprehensive and complex. Controlling compensatory and unnecessary motion in the foot during the propulsive phase of gait, is critical to the success of our biomechanical treatment plans. Forefoot correction is also what often distinguishes a custom foot orthotic from generic arch supports, which in most cases, offer little or no correction of forefoot varus/valgus forefoot deformities or control of hypermobility present due to abnormal ground reactive forces, particularly in the 1st metatarsal phalangeal joint. Increasing the propulsive power of the human foot is often the primary goal of any effective functional foot orthotic device.
Pronation is generally defined as a natural inward rolling motion of the foot during walking or running. The arch flattens, and the foot absorbs shock and adapts to uneven surfaces. Excessive pronation in the forefoot may cause increased pressure on the medial (inside) side of the forefoot, risk of conditions like bunions (hallux valgus) and overuse injuries or may lead to excessive toe deformity and instability in push-off
Supination is generally defined as an outward rolling motion of the foot during gait. The arch remains higher, and the foot becomes a rigid lever for propulsion. Increased pressure on the lateral (outer) side of the forefoot. Associated with higher risk of stress fractures, ankle sprains, rigid hammertoe deformities and calluses under the metatarsal heads and on the outer toes. Reduced shock absorption, potentially leading to knee and hip issues.
Biomechanical deformities of the forefoot can be classified as either fixed (non-reducible) or flexible (reducible). Generally speaking, forefoot varus or supinatus will lead to excessive pronation during the propulsive phase of gait. Forefoot valgus and/or rigid plantarflexed 1st ray deformities will lead to over-supination type conditions.
Deformities of the forefoot are treated by orthotics through the use of a forefoot post. It can either be “intrinsic” or built into the shape of the frame of the orthotic, or “extrinsic” or added as a flat, solid addition to the plantar surface of the frame. Combinations also exist primarily in cases of high degree deformities. Posts can be either varus or valgus. Intrinsic posting is generally more easily tolerated and fits well in shoes. The amount of correction built into the orthotic depends on the deformity measured during the biomechanical examination, the range of motion of the first ray and any variations in the metatarsal parabola. The default correction when no measurement is indicated on the prescription, is to “balance” the forefoot correction to perpendicular to the vertical bisection of the heel.
The next decision to be made in the forefoot construction of the orthotic device is the use of an extension. Extensions are either sulcus length or full length. Extensions are helpful for a variety of reasons, they provide extra cushioning to the plantar metatarsal head areas, and provide for placement of pads and accommodations of the forefoot. The next post in this series will focus on more detail in orthotic construction to control excessive pronation and supination of the forefoot.
