Knee Extensor Strength Does Not Protect Against Incident Knee Symptoms at 30 Months in the Multicenter Knee Osteoarthritis (MOST) Cohort

ObjectiveKnee extensor weakness has not been associated consistently with the risk for incident knee pain. Additionally, the balance of hamstring-to-quadriceps strength (H:Q ratio) may affect risk and has not been studied. The authors determined whether knee extensor weakness or muscle imbalance is a risk factor for development of frequent knee pain or stiffness and whether the effect is modified by lower limb alignment.DesignObservational study.SettingCommunity.ParticipantsCommunity-dwelling adults ages 50-79 years with or at risk of knee osteoarthritis based on obesity, knee injury, or surgery. A total of 1269 knees from women and 1006 knees from men without frequent knee symptoms at baseline and with 15- or 30- month follow-up outcome data were included.Assessment of Risk FactorsIsokinetic knee extensor and flexor strength as well as radiographic hip-knee-ankle alignment were measured at baseline. H:Q ratio was dichotomized, with normal being considered to be ≥0.6.Main Outcome MeasurementsFrequent knee symptoms at 15- or 30-month follow-up (frequent knee pain, aching, or stiffness on most days of the past month reported at both telephone contact just before and at visit).ResultsMean ± SD age was 62.2 ± 8.0 years and mean body mass index (BMI) was 30.1 ± 5.4 kg/m2. Mean peak knee extensor strength (KES) was 132.6 ± 42.4 and 76.9 ± 25.3 N·m in men and women, respectively. Approximately 50% of knees in men and 59% of knees in women had an H:Q ratio <0.6. A total of 307 of 2275 eligible knees developed frequent knee symptoms at follow-up. Logistic regression controlling for age, BMI, femoral neck bone mineral density, activity score, and baseline Kellgren Lawrence grade revealed that neither KES nor H:Q ratio predicted the development of knee symptoms in gender-stratified or combined analyses. These results were unaffected by adjusting for lower limb alignment.ConclusionsNeither concentric quadriceps strength nor H:Q ratios predicted the development of frequent knee symptoms at 15- or 30-month follow-up in this cohort.