Forefoot varus is a foot misalignment that causes the inside edge of the first metatarsal to sit higher than the outside. This usually requires compensation with increased pronation in the subtalar joint during weight-bearing activities.
This study compared static foot measurements, foot dimensions and force plate measures in subjects with high, neutral and low forefoot varus during single-leg stance. Positive correlations existed between forefoot angle and relaxed rearfoot and navicular angles.
Symptoms
The term “forefoot varus” describes an inverted position of the forefoot relative to the rear foot at the level of the metatarsal-phalangeal (MPJ) joints. It is a common pathomechanical entity associated with excessive pronation. Ten to fifteen percent of all feet treated by chiropractors have this condition. The etiology of this condition is primarily soft tissue restrictions that lead to overpronation.
To compensate for this foot type the medial arch flattens out too much in weight bearing and excessively pronates. The resulting overpronation puts tremendous strain on the lateral column of the foot and ankle. This results in an overload of the plantar fascia which is most often referred to as heel pain.
This pathomechanical condition also causes the big toe to move into a pronated position as it attempts to support the overpronation of the front foot. This puts additional strain on the plantar fascia and also can cause a stress fracture of the calcaneal (heel) bone.
This foot type is a common cause of Achilles tendinitis. The reason for this is that over time excessive subtalar joint (STJ) pronation will maintain the limb in an internally rotated position causing the achilles tendon to twist as it tries to make contact with the ground during early propulsive phase of the gait cycle. This twisting of the achilles can be quite severe and often causes a snapping sensation.
Diagnosis
When the head and neck of the talus remain in the inverted position and the metatarsal joints are maximally pronated it is referred to as forefoot varus. It is important to differentiate this construct from forefoot supinatus which occurs when the calcaneus is in a plantarflexed and inverted position. This foot type has a very low arch profile on both non-weight bearing and weight-bearing examinations and is seen commonly in cycling communities.
In functional forefoot varus the problem is due to soft tissue restrictions and is not a structural deformity of the foot or ankle. This condition can be difficult to detect clinically. A good diagnostic tool is a forefoot angle measurement which can be performed in a non-weight bearing position and ranges from 1-8 degrees. A measurement that is greater than 8 is considered high forefoot varus.
If left untreated forefoot varus can cause a compensatory pronation pattern of the foot that will twist the ankle and lower leg during the propulsive phase of gait. This repeated movement causes stress on the foot and ankle structures such as the shin muscles, Achilles tendon, and the plantar fascia. This can lead to pain, fatigue, and increased injury risk. Research has shown that forefoot varus is associated with increased medial patellofemoral joint (PFJ) cartilage damage compared to forefoot valgus.
Treatment
In a functional forefoot varus the forefoot appears inverted relative to the rearfoot because of a soft tissue restriction. It is not a congenital deformity but rather an abnormality that occurred over time. In addition to applying a heel cup and limiting shoe selection, Chiropractic Manipulative Therapy should be delivered to the involved joints of the foot and ankle.
In those with uncompensated forefoot varus, the foot cannot assume a plantargrade position on weightbearing and compensation must occur at the subtalar joint (STJ). This results in excessive calcaneal eversion causing the STJ to pronate for longer than normal and delay resupination.
Those with uncompensated forefoot varus may have pain in the metatarsal (MT) area because of increased pressure on the MT joints from excessive eversion. A kinetic wedge foot orthosis or rocker sole can be used to off-load the MT joints and reduce symptoms. In some cases, a toe sleeve or pad can be placed under the first MT head to relieve pain from hallux limitus or rigidus. Those with lesser toe deformities such as hammer, claw or mallet toes can benefit from an MT bar or cushioned insole to off-load the MT joints. Hallux abducto valgus can be treated with a plantar plate, medial cuneiform bar or a valgus control shoe insert to alleviate the pressure under the first MT head.
Prevention
During normal ontogenetic (growth) development the head and neck of the talus is plantarflexed (pointed downward by the big toe) and inverted (rolled inward). In the forefoot varus deformity it fails to straighten out to align with the rearfoot. This is a congenital condition present from birth. The most common cause is a valgus torsion of the head/neck of the talus from its neutral position at birth due to soft tissue restriction.
Often this forefoot varus is compensated by excessive pronation of the foot. The excessive pronation in turn causes the talonavicular and calcaneocuboid joints to also pronate. This overpronation can also result in excessive lateral (outward) rotation of the talus that then rotates the lower leg/ ankle causing iliotibial band syndrome.
Another injury related to forefoot varus is repetitive dorsiflexion of the great toe during the propulsive phase of gait that puts a lot of strain on the great toe plantar fascia. This repeated dorsiflexion can eventually cause a stress fracture of the great toe.
Forefoot varus can lead to a functional short leg by lowering the ipsilateral pelvic articular bone (one of the pelvic bones). This can cause excessive compression of the spinal discs as well as narrowing of the greater sciatic notch in the pelvis. This can entrap the sciatic nerve if left untreated.