Biomechanical and clinical factors related to stage I posterior tibial tendon dysfunction.

STUDY DESIGN: Case control. OBJECTIVES: To investigate differences in arch height, ankle muscle strength, and biomechanical factors in individuals with stage I posterior tibial tendon dysfunction (PTTD) in comparison to healthy individuals. BACKGROUND: PTTD is a progressive condition, so early recognition and treatment are essential to help delay or reverse the progression. However, no previous studies have investigated stage I PTTD, and no single study has measured static anatomical structure, muscle strength, and gait mechanics in this population. METHODS: Twelve individuals with stage I PTTD and 12 healthy, age- and gender-matched control subjects, who were engaged in running-related activities, participated in this study. Measurements of arch height index, maximum voluntary ankle invertor muscle strength, and 3-dimensional rearfoot and medial longitudinal arch kinematics during walking were obtained. RESULTS: The runners with PTTD demonstrated significantly lower seated arch height index (P = .02) and greater (P = .03) and prolonged (P = .05) peak rearfoot eversion angle during gait, compared to the healthy runners. No differences were found in standing arch height index values (P = .28), arch rigidity index (P = .06), ankle invertor strength (P = .49), or peak medial longitudinal arch values (P = .49) between groups. CONCLUSION: The increased foot pronation is hypothesized to place greater strain on the posterior tibialis muscle, which may partially explain the progressive nature of this condition.

The role of tibialis posterior fatigue on foot kinematics during walking.

BACKGROUND: The purpose of this study was to investigate the effect of localised tibialis posterior muscle fatigue on foot kinematics during walking. It was hypothesised that following fatigue, subjects would demonstrate greater forefoot and rearfoot motion during walking. It was also postulated that the magnitude of the change in rearfoot motion would be associated with standing anatomical rearfoot posture. METHODS: Twenty-nine subjects underwent an exercise fatigue protocol aimed at reducing the force output of tibialis posterior. An eight camera motion analysis system was used to evaluate 3D foot kinematics during treadmill walking both pre- and post-fatigue. The anatomical rearfoot angle was measured during standing prior to the fatigue protocol using a goniometer. RESULTS: Peak rearfoot eversion remained unchanged following the fatigue protocol. Although increases in rearfoot eversion excursion were observed following fatigue, these changes were of a magnitude of questionable clinical significance (<1.0 degrees ). The magnitude of the change in rearfoot eversion due to fatigue was not associated with the anatomical measurement of standing rearfoot angle. No substantial changes in forefoot kinematics were observed following the fatigue protocol. CONCLUSIONS: These data indicate that reduced force output of the tibialis posterior muscle did not alter rearfoot and forefoot motion during gait. The anatomical structure of the rearfoot was not associated with the dependence of muscular activity that an individual requires to maintain normal rearfoot kinematics during gait.