title: 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 muscle group weakness and related hip joint velocity reduction and stiff-knee gait (SKG) during walking in healthy individuals.
  
  
  METHODS
  A load of 5% of each individual's body weight was placed on non-dominant thigh of 15 neurologically intact, able-bodied participants (average age: 22.4 ± 0.81 years). For 33 min (135 s × 13 repetitions × 5 s rest), a passive stretch (PS) was applied with the load in place until hip flexor muscle strength dropped from 5/5 to 3+/5 according to manual muscle test. All participants underwent gait analysis before and after PS to compare sagittal plane hip, knee, and ankle kinematics and kinetics and temporo-spatial parameters. Paired t-test was used to compare pre- and post-stretch findings and Pearson correlation coefficient (r) was calculated to determine strength of correlation between SKG parameters and gait parameters of interest (p < 0.05).
  
  
  RESULTS
  Reduced hip flexion velocity (mean: 21.5%; p = 0.005) was a contributor to SKG, decreasing peak knee flexion (PKF) (-20%; p = 0.0008), total knee range (-18.9%; p = 0.003), and range of knee flexion between toe-off and PKF (-26.7%; p = 0.001), and shortening duration between toe-off to PKF (-16.3%; p = 0.0005).
  
  
  CONCLUSIONS
  These findings verify that any treatment protocol that slows hip flexion during gait by weakening iliopsoas muscle may have great potential to produce SKG pattern combined with reduced gait velocity.
authors.affiliation: İstanbul University, Faculty of Health Sciences, Physiotherapy and Rehabilitation Division, İstanbul, Turkey. Electronic address: ekin.akalan@gmail.com.
authors.forename: N Ekin
authors.initials: NE
authors.lastname: Akalan
authors.affiliation: Institute of Biomedical Engineering, Boğaziçi University, Kandilli Campus, İstanbul, Turkey.
authors.forename: Shavkat
authors.initials: S
authors.lastname: Kuchimov
authors.affiliation: İstanbul University, Institute of Health Sciences, Cerrahpaşa Medical School, İstanbul, Turkey.
authors.forename: Adnan
authors.initials: A
authors.lastname: Apti
authors.affiliation: İstanbul University, İstanbul School of Medicine, Department of Orthopedics and Traumatology, İstanbul, Turkey.
authors.forename: Yener
authors.initials: Y
authors.lastname: Temelli
authors.affiliation: Roessingh Rehabilitation Center, Enschede, Netherlands.
authors.forename: Anand
authors.initials: A
authors.lastname: Nene
mesh_terms: D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait; D064368:Healthy Volunteers; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength; D016658:Psoas Muscles / Q000502:physiology*; D016059:Range of Motion, Articular; D055815:Young Adult
keywords: Gait; Hip; Iliopsoas; Knee; Stiff knee; Stretching; Velocity; Weakness