Unit
- Bony structure: The foot contains 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments. The hindfoot (talus and calcaneus), midfoot (navicular, cuboid, three cuneiforms), and forefoot (metatarsals and phalanges) form a complex arch system that supports weight and absorbs shock.
- Arches: The medial longitudinal arch, lateral longitudinal arch, and transverse arch distribute forces during standing and walking. Dysfunction in any arch can lead to conditions such as plantar fasciitis or flat feet.
- Ligaments and tendons: The plantar fascia, Achilles tendon, and peroneal tendons provide stability and enable movement. Overuse or injury to these structures is a common source of foot pain.
- Muscle groups: Intrinsic muscles control fine movements of toes, while extrinsic muscles originate in the lower leg and control ankle and foot motion. Weakness in these muscles affects gait and balance.
- Nerves and circulation: The tibial and peroneal nerves supply sensation; the dorsalis pedis and posterior tibial arteries ensure blood flow. Neuropathy or vascular compromise can complicate pedorthic management.
- Skin and soft tissue: The skin on the foot is thicker on weight-bearing areas. Calluses, corns, and ulcers can develop from abnormal pressure, making proper footwear essential.
- Age-related changes: Children's feet are cartilaginous and develop arches by age 10. Older adults lose fat padding and experience reduced elasticity, increasing injury risk.
- Biomechanical axis: The subtalar joint axis orientation varies among individuals, affecting how forces transmit through the foot. Understanding these variations guides orthotic design.
- Gait cycle phases: The stance phase accounts for 60 percent of gait and includes heel strike, midstance, and toe off. The swing phase covers the remaining 40 percent with limb advancement. Recognizing timing of abnormal pressures during these phases is critical for effective orthotic intervention.
- Foot type variations: Foot posture ranges from neutral to pronated (flatfoot) or supinated (high arch). Each type alters load distribution across the plantar surface. Different orthotic modifications, such as posting or arch supports, are required to accommodate these variations and restore balanced gait.
- Shoe construction considerations: Last shape, toe box depth, heel counter stiffness, and sole flexibility directly affect fit and function. Pedorthic interventions may involve modifying the shoe itself, such as stretching the toe box or reinforcing the heel counter, or selecting specific footwear that accommodates the patient's foot type.
- Common forefoot pathologies: Hallux valgus (bunion), hammer toe, and metatarsalgia result from biomechanical imbalances and improper shoe fit. Orthoses can offload pressure, realign joints, and reduce pain through the use of metatarsal pads, toe spacers, or custom orthotic plates.
- Material properties in orthoses: EVA, polypropylene, cork, and carbon fiber offer varying degrees of rigidity, shock absorption, and weight. Selection of material depends on the patient's activity level, severity of deformity, and the amount of motion control needed for effective treatment.
- Weight distribution and pressure: During quiet standing, approximately 50 percent of body weight is borne by the heel and 50 percent by the forefoot. Pedorthic devices must redistribute pressure to prevent skin breakdown, particularly in diabetic patients where even small pressure points can lead to ulcers.
Terminology
- Pedorthics
- The practice of designing, manufacturing, fitting, and modifying footwear and foot orthoses to alleviate foot problems.
- Orthosis
- A custom-made device worn inside the shoe to correct or compensate for foot deformities or imbalances.
Quick Revision
- The foot's complex bony, ligamentous, and muscular structures work together for weight bearing and locomotion.
- Arch architecture is critical for force distribution and is a key consideration in orthotic design.
- Age, pathology, and individual anatomy influence the selection of pedorthic interventions.