Association between long-term quadriceps weakness and early walking muscle co-contraction after total knee arthroplasty.

INTRODUCTION: Quadriceps weakness is one of the primary post-operative impairments that persist long term for patients after total knee arthroplasty (TKA). We hypothesized that early gait muscle recruitment patterns of the quadriceps and hamstrings with diminished knee performance at 3months after surgery would be related to long-term quadriceps strength at 1year after TKA.
METHODS: Twenty-one subjects who underwent primary unilateral TKA and 14 age-matched healthy controls were analyzed. At 3months after TKA, the maximum voluntary isometric contraction of the quadriceps and a comprehensive gait analysis were performed. Quadriceps strength was assessed again at 1year after surgery.
RESULTS: Quadriceps muscle recruitment of the operated limb was greater than the non-operated limb during the loading response of gait (p=0.03), but there were no significant differences in hamstring recruitment or co-contraction between limbs (p>0.05). There were significant differences in quadriceps muscle recruitment during gait between the non-operated limbs of the TKA group and the healthy control group (p<0.05). The TKA group showed a significant inverse relationship between one year quadriceps strength and co-contraction (r=-0.543) and hamstring muscle recruitment (r=-0.480) during loading response at 3months after TKA.
CONCLUSIONS: The results revealed a reverse relationship where stronger patients tended to demonstrate lower quadriceps recruitment at 3months post-surgery that was not observed in the healthy peer group. The altered neuromuscular patterns of the quadriceps and hamstrings during gait may influence chronic quadriceps strength in individuals after TKA. LEVEL OF EVIDENCE: III.