title: IMPROVEMENTS IN KNEE EXTENSION STRENGTH ARE ASSOCIATED WITH IMPROVEMENTS IN SELF-REPORTED HIP FUNCTION FOLLOWING ARTHROSCOPY FOR FEMOROACETABULAR IMPINGEMENT SYNDROME.
abstract: BACKGROUND
  Recovery of strength is critical for return to sport, and is a known predictor of functional outcomes in post-surgical orthopedic populations. Muscle weakness is a known impairment in patients with femoroacetabular impingement syndrome (FAIS) but whether improvements in muscle strength after arthroscopy are associated with improved hip function is unknown.
  
  
  OBJECTIVE
  To examine the relationships between changes in hip and thigh muscle strength and self-reported function in athletes undergoing arthroscopy for FAIS.
  
  
  METHODS
  Single cohort descriptive and correlational study.
  
  
  METHODS
  Twenty-eight athletes underwent strength testing and completed the Hip Outcome Score Activities of Daily Living (HOS-ADL) and Sports (HOS-S) subscales prior to and six months after surgery. Isokinetic knee extension and flexion strength were measured using a Biodex dynamometer at 60 °/s and 300 °/s. Isometric hip abduction strength was measured using a custom dynamometer. Changes in strength, limb symmetry, and HOS scores were assessed using paired t-tests. Spearman's rank correlations were used to examine relationships between change in involved limb strength and change in HOS scores.
  
  
  RESULTS
  Subjects were tested an average of 32 days before and 178 days after surgery. HOS-ADL and HOS-S subscales improved by a mean of 19.0 ± 21.1 and 23.8 ± 31.9, respectively, over time (p< 0.001). Hip abduction strength did not increase over time in either limb (p≥ 0.27). Involved limb knee flexion and extension strength did not increase significantly over time (p-values: 0.10-0.48) with the exception of knee extension at 300 °/s (p = 0.04). Uninvolved limb knee extension strength at both velocities and knee flexion strength at 60 °/s improved significantly over time (p< 0.012). Increases in knee extension strength (60 °/s) of the involved limb were significantly correlated with improvements on the HOS-ADL (r = 0.431;0= 0.025) and HOS-S (r = 0.439; p = 0.025). There were no significant relationships between changes in involved limb hip abduction or knee flexion strength and HOS subscales (p≥0.123).
  
  
  CONCLUSIONS
  Improvements in knee extension strength were associated with improvements in self-reported hip function in athletes following arthroscopy for FAIS. Individuals with knee extension strength deficits prior to surgery may benefit from targeted knee extension strengthening during post-operative rehabilitation to improve functional outcomes.
  
  
  METHODS
  Level III (non-randomized controlled cohort study).
authors.affiliation: The Ohio State University Wexner Medical Center Sports Medicine, Columbus, OH, USA.
authors.forename: Chelseana C
authors.initials: CC
authors.lastname: Davis
authors.affiliation: Trauma and Total Joint Reconstruction, Orthopaedic One, Columbus, OH, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Ellis
authors.affiliation: Sports Medicine Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
authors.forename: Ajit K
authors.initials: AK
authors.lastname: Amesur
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hewett
authors.forename: Stephanie
authors.initials: S
authors.lastname: Di Stasi
keywords: femoroacetabular impingement syndrome; hip strength; knee strength