A fixed osseous deformity in which the posterior bisection of the calcaneus is inverted relative to vertical when the subtalar joint is in its defined neutral position.
Very common. Greater then 4 degrees in 98% of the population in one study maybe just a normal variant
Assumed to be due to a failure of the calcaneus and tibia to fully derotate from their foetal varus positions.
1) Tibial varum (tibial influence) – distal third of tibia is in varus – due to failure of tibia to correct from infantile position; genu varum of Blount’s disease
2) Varus angulation of subtalar joint
3) Varus position of calcaneus – retention of foetal position
Rearfoot varus is the sum total of all three of the above
A varus position of the rearfoot complex may also be due to trauma.
A varus position of the calcaneus is considered normal up to ages 7 – 8 years.
All 3 causes place the foot in an inverted position when the STJ is in its defined neutral position the subtalar joint must pronate to bring the medial side of the foot to the ground. The compensation for a rearfoot varus will depend on the degree of the deviation and the amount of motion available at the STJ:
• No ROM at STJ – foot can not pronate to get medial side of foot to ground. Rare
• Foot strikes ground laterally and remains inverted.
• Poor shock absorber pathologies associated with poor shock absorption.
• lateral ankle sprains common
• Lateral shoe wear; hyperkeratosis under 5th MPJ (usually severe)
2) Fully compensated:
• Adequate ROM of STJ to bring medial side of foot to the ground
• Contact period pronation of foot is assumed to be more rapid and prolonged with delayed resupination
• Haglund’s deformity/retrocalcaneal bursitis is common
• callus formation plantar to metatarsal head 2 to 4 is assumed to be more common in those with rearfoot varus – due to dorsiflexion mobility of the first ray from the excessive subtalar joint pronation
• Arch height will be medium during weightbearing and non-weightbearing
• Increased risk for tissue damage associated with excessive pronation
• Not considered to be a very ‘destructive’ foot type with symptoms tending to be milder
• During stance the calcaneus will appear vertical and gait will not necessarily appear ‘abnormal’ – there will be no ‘Helbings’ sign (medial bowing of the achilles tendon)
3) Partially compensated:
• Some motion is available at STJ, but no sufficient for full compensation
• Patients walk with foot inverted to the ground, then abduct during propulsion
• Pathomechanics and clinical features are between the fully and uncompensated types
Orthoses with medial wedging/posting to bring ground up to foot to prevent need for compensatory pronation.