Weakening iliopsoas muscle in healthy adults may induce stiff knee pattern

Abstract

Objective: The goal of the present study was to investigate the relationship between iliopsoas musclegroup weakness and related hip joint velocity reduction and stiff-knee gait (SKG) during walking inhealthy individuals.Methods: A load of 5% of each individual's body weight was placed on non-dominant thigh of 15neurologically intact, able-bodied participants (average age: 22.4± 0.81 years). For 33 min (135 s 13repetitions 5 s rest), a passive stretch (PS) was applied with the load in place until hip flexor musclestrength dropped from 5/5 to 3þ/5 according to manual muscle test. All participants underwent gaitanalysis before and after PS to compare sagittal plane hip, knee, and ankle kinematics and kinetics andtemporoespatial parameters. Paired t-test was used to compare pre- and post-stretch Şndings andPearson correlation coefŞcient (r) was calculated to determine strength of correlation between SKGparameters and gait parameters of interest (p< 0.05).Results: Reduced hipflexion velocity (mean: 21.5%; p ¼ 0.005) was a contributor to SKG, decreasing peakkneeflexion (PKF) ( 20%; p ¼ 0.0008), total knee range ( 18.9%; p ¼ 0.003), and range of knee flexionbetween toe-off and PKF ( 26.7%; p ¼ 0.001), and shortening duration between toe-off to PKF ( 16.3%;p¼ 0.0005).Conclusion: TheseŞndings verify that any treatment protocol that slows hip flexion during gait byweakening iliopsoas muscle may have great potential to produce SKG pattern combined with reducedgait velocity.