1. Field of the Invention
The present invention relates to a foot support for a human foot.
2. Description of Related Art
The foot comprises various ligaments, muscles, tendons, and bones that flexibly respond to shifting weight as a person walks in a normal heel to toe gait. A foot may generally be described as having a toe portion, a forefoot portion, a midfoot portion, and a heel portion. The toe portion is made up of the phalanx bones and associated ligaments, muscles, and tendons for the great or first toe (otherwise known as the hallux), second toe, third toe, fourth toe, and fifth toe. The forefoot portion is made up of the distal portion of the first through fifth metatarsal bones, also called the metatarsal heads, and the associated ligaments, muscles, and tendons. The midfoot portion is made up of the proximal portion of the first through fifth metatarsals and the cuneiforms, cuboid, and navicular bones and the associated ligaments, muscles, and tendons. The heel portion is made up of the calcaneus and talus bones and associated ligaments, muscles, and tendons. The medial longitudinal arch runs from the heel portion to the forefoot portion of the foot.
Foot flexibility allows for shock absorption and a normal foot will pronate slightly in the midfoot portion when body weight is transferred along the foot during locomotion. When the foot is too flexible it cannot properly support the body and an individual may develop pain in her foot, legs, knees, hip, back, or neck. An overly flexible foot is often caused by metatarsal-cuneiform joints that exhibit hypermobility. Between forefoot loading and heel lift, weight is transferred from the lateral aspect of the foot to the medial aspect of the foot. During this transfer, the medial longitudinal arch collapses until the metatarsal-cuneiform joints lock at the peak of their dorsiflexion. If the metatarsal-cuneiform joints are too flexible, the arch collapses more completely than it should. Over time, normal arches break down due to this continuous abuse and the individual will develop a forefoot varus deformity in one or both feet. This condition is more commonly known as “flat feet.” It is estimated that 75% of the population will at some time develop foot problems, and of these individuals, 25% suffer from flat feet or pes planus.
There are varying degrees of flatfoot deformity that can occur in the legs, rearfoot, and forefoot. In a normal foot, the weight is centered on the lateral side of the heel during heel strike. Then the weight is distributed to the medial side of the foot during forefoot loading and the foot is allowed to pronate slightly, i.e., the medial longitudinal arch collapses to a certain point. During heel lift the weight is directed towards the first metatarsal head and then down the axis of the hallux at toe off. For an individual with a flat foot, the weight is distributed differently due to over-pronation and forefoot varus deformity. At heel strike the weight is more central to the heel, and then during forefoot loading, the weight is shifted immediately to the medial aspect of the foot due to the over-collapsed medial longitudinal arch. In an attempt to correct for the drastic shift in weight to the medial aspect of the foot, weight is shifted past the first metatarsal head and is concentrated at the second through fourth metatarsal heads during heel lift. At toe off, the weight is transferred to a medial aspect of the hallux. When a human foot is allowed to over-pronate in this way, more strain is placed on the ligaments, muscles, tendons, and bones of the entire body because the foot is not stable. Problems such as plantar fasciitis, bunions, shin splints, neuromas, tendonitis, and knee, hip, or back pain can occur.
Various orthotics and insoles are known in the art. Most are designed to provide comfort through cushioning. Some are designed to support feet with high arches. Others provide support for the medial longitudinal arch and are designed to prevent the talar-navicular and calcaneal-cuboid joints from exhibiting hypermobility. None of these products rebalance a foot having a forefoot varus deformity. As a result, individuals who use the orthotics and insoles known in the art to support the medial longitudinal arch in their feet, often complain that such products are uncomfortable and cause soreness in their arches.
U.S. Pat. No. 4,747,410 discloses an orthotic insert having a toe region, a forefoot region, a midfoot region, and heel cup. The insert features an anterior varus wedge that has a greater thickness at the medial side of the foot than the lateral side and a heel cup for stabilizing various components of the heel. The orthotic also features a medial shelf that is positioned to substantially underlie and support the first ray of the foot. In U.S. Pat. No. 4,333,472, a wedge is disclosed having a greater thickness at the medial side of the foot than the lateral side and positioned between the first through fifth metatarsals heads. Neither of these prior devices fully supports or rebalances a flat foot.