The weightbearing component of the lower extremity exam provides key information to identify the acquired pes plano valgus deformity and grade its severity. Decreased medial longitudinal arch height (navicular differential or drop) from off to on weightbearing is a useful screening tool. Significant drop with other changes such as medial and plantar prominence of the talus, abduction of the midfoot and frontal plane rotation of the hallux signal the presence of compensation and the abnormal foot position often associated with the onset of deformities.
Assessment of the relaxed calcaneal stance position (RCSP) to determine the degree of heel valgus on weightbearing is useful in grading severity. Systems such as the Valmassy formula can help the clinician to determine when heel valgus is excessive for a young child of a particular age.4 High heel valgus may indicate a frontal planal dominance to the deformity and, in some cases, may be associated with changes in the transverse plane such as medial talar deviation and midfoot abduction.
When it comes to flatfoot and gait, the propulsive child approaching 3 years of age demonstrates characteristic findings when an excessively pronated foot is present. Typical findings include a marked abducted angle of gait (which may be reduced when superstructural in-toe is contributing to the deformity). It is also common to see late midstance and propulsive phase pronation of the subtalar and midtarsal joints. This is characteristically marked by continued eversion of the calcaneus after heel lift. Shortened stride length with poor quality propulsion, medial roll of the hallux and lifting are often visible as well.