Weight bearing ankle dorsiflexion range of motion in idiopathic pes cavus compared to normal and pes planus feet

Abstract

Background: Various factors are considered influential in the development of pes cavus. Short tendo-Achilles is one factor that has been hypothesised as a deforming mechanism of ‘idiopathic’ pes cavus. Objective: To measure tendo-Achilles length in subjects with idiopathic pes cavus, compared to normal and pes planus feet, and to examine the relationship between tendo-Achilles length and foot type. Method: Fifty-three healthy volunteers (34 female, 19 male) were recruited to encompass a wide range of foot types, varying in degree of cavoid, normal and planus features. Foot type was measured weight bearing using the Foot Posture Index (FPI). The length of the tendo-Achilles was also measured weight bearing using the lunge test. Results: Twenty-four subjects with pes cavus, 24 subjects with a normal foot type and five subjects with pes planus completed the study. Lunge angle in the pes cavus group was significantly less than the normal and pes planus groups ( P < 0.001). A strong, positive correlation was identified between tendo-Achilles length and foot type ( r = 0.757, P < 0.001; r 2 = 57.3%). Conclusion: Distinct differences exist in tendo-Achilles length in individuals with a pes cavus foot type, compared to normal and pes planus feet. A strong positive relationship between tendo-Achilles shortness and pes cavus severity has been identified.