The subtalar joint provides pronation and supination:
PRONATION: A combination of Eversion, Dorsiflexion, and Abduction of the foot.
SUPINATION: A combination of Inversion, Plantarflexion, and Adduction of the foot.
Note that normal inversion is approximately 20 degrees: Normal eversion is approximately 1 degrees.
Subtalar pronation will place that athlete at higher risk for the following injuries:
Sesmoiditis
Plantar Fasciitis
Acchilles Tendinopathy
Peroneal Tendinopathy
Medial Shin Pain
Patellar Tendinopathy
Patellofemoral Syndrome
Metatarsal Stress Fractures
Navicular Stress Fractures
Fibular Stress Fractures
Note that subtalar pronation occurs usually as compensation for another biomechanical abnormality.
REARFOOT VARUS: The most common biomechanical foot problem. It causes about 85% of cases of pronation due to foot abnormalities.. This is a inversion of the rearfoot. The subtalar joint will pronate to compensate.
FOREFOOT VARUS: A structural inversion of the forefoot in relation to the rearfoot. The subtalar joint must pronate to allow the medial aspect of the foot to make contact with the ground. Causes about 10-15% of cases of subtalar pronation due to intrinsic foot problems.
ANKLE EQUINUS: Occurs when dorsiflexion of the ankle is less than 10-20 degrees. Ankle dorsiflexion is necessary to allow the tibia to rotate over the foot during the stance phase. Ankle equinus may be caused by bony limitations or by tightness/shortening of the acchilles complex. Equinus will cause subtalar pronataion, in order to use the dorsiflexion component of pronation. This may manifest as a bouncy gait: weight is transferred prematurely to the forefoot. Athletes are predisposed to injuries of the plantar fascia, metatarsal, toes. Compensation for limited ankle dorsiflexion may alos lead to ligament sprains, and calf muscle injuries.
TIBIA VARUM: Lateral deviation, or bowing of the tibia. This causes inversion of the foot with heel-strike. Subtalar pronation occurs to allow the medial aspect of the foot to contact the ground.
TIBIAL EXTERNAL TORSION: This results in an abducted gait leading to excessive varus position at heel strike. This produces greater lateral stress to the lower limb; such as the iliotibial band. Subtalar pronation follows.
GENU VARUM: A bow-legged stance leads to increase varus heel-strike and greater lateral stress. Subtalar pronation occurs to allow the medial aspect of the foot to contact the ground. This may also predispose to pattelafemoral disorder.
GENU VALGUM: A knock-kneed stance causes direct pronation of the foot as the center of gravity is medial to th subtalar joint. This is not a compensatory subtalar pronation.
Observation: When the patient is walking, observe foot postion at heel strike, foot position at midstance, and foot position at toe-off.
Resting Calcaneal Stance: Measure the angle of the calcaneous to the supporting surface in resting stance.
Neutral Calcaneal Stance: Measure the angle of the calcanous when the subtalar joint is neutral to the surface.
Tibial Angulation: With the subtalar joint in neutral, measure the angle of the bisection of the lower leg with respect to vertical.
Tibial Torsion: Measure the degree of tibial torsion by having the patient lie supine, with the knee in the frontal plane, and with a goniometer placed on the malleoli.
Midtarsal Joint: Observe the angle of the midtarsal joint when the subtalar joint is in neutral and the foot is held just distal to the talonavicular and calcaneoucuboid joints.
Ankle Joint: Measure range of motion of dorsiflexion and plantarflexion.
Subtalar Joint: The calcanous is inverted and everted. Assess the angle between the bisection of the calcanous and and the posterior aspect of the leg.
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In the acute phase, most injuries will benefit from the R.I.C.E regime
Many injuries can be prevented by following some general rules for injury prevention