Hip strengthening reduces symptoms but not knee load in people with medial knee osteoarthritis and varus malalignment: a randomised controlled trial.
OBJECTIVE
To determine whether hip abductor and adductor muscle strengthening reduces medial compartment knee load and improves symptoms in people with medial tibiofemoral OA and varus malalignment.


METHODS
In a randomised controlled trial, 89 participants were randomly allocated to a hip strengthening group or to a control group with no intervention. The strengthening group performed a physiotherapist-supervised home exercise program targeting the hip abductor and adductor muscles for 12 weeks. The primary outcome was the peak external knee adduction moment measured using three-dimensional gait analysis by a blinded assessor. Secondary outcomes included a pain numeric rating scale, Western Ontario and McMaster Universities Osteoarthritis Index, step test, stair climb test, maximum isometric strength of hip and quadriceps muscles and participant-perceived rating of overall change. Intention-to-treat analyses were performed using linear regression modelling adjusting for baseline outcomes and other characteristics.


RESULTS
The trial was completed by 76/89 participants (85%). There was no significant between-group difference in change in the knee adduction moment [mean difference (95% confidence interval (CI)) 0.134 (-0.069 to 0.337) Nm/BW x HT%]. All pain, physical function and muscle strength measures showed significantly greater improvement in the strengthening group (all P<0.05). The relative risk (95% CI) of participant-perceived overall improvement in the strengthening group compared to the control group was 20.02 (6.21-64.47).


CONCLUSIONS
Although strengthening the hip muscles improved symptoms and function in this patient group, it did not affect medial knee load as measured by the knee adduction moment. Thus it is unlikely that hip muscle strengthening influences structural disease progression.


BACKGROUND
ACTR12607000001493.
Bennell
K L
KL
Centre for Health, Exercise & Sports Medicine, School of Physiotherapy, University of Melbourne, Australia. k.bennell@unimelb.edu.au
Hunt
M A
MA
Wrigley
T V
TV
Hunter
D J
DJ
McManus
F J
FJ
Hodges
P W
PW
Li
L
L
Hinman
R S
RS
D000368:Aged; D017760:Bone Malalignment / Q000503:physiopathology / Q000628:therapy*; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005684:Gait / Q000502:physiology; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000628:therapy*; D017063:Outcome Assessment, Health Care; D010146:Pain / Q000209:etiology / Q000503:physiopathology; D059408:Pain Management; D010147:Pain Measurement; D012044:Regression Analysis; D016474:Weight-Bearing / Q000502:physiology