Muscle strength loss in the lower limb after total knee arthroplasty.

OBJECTIVE: This study aimed to examine functional mobility and strength loss in the ankle plantarflexors and dorsiflexors and knee extensors and flexors after total knee arthroplasty.
DESIGN: This was a prospective, longitudinal cohort study. Maximal voluntary isometric contractions and gait speed assessments were performed before and after total knee arthroplasty.
RESULTS: Twenty patients undergoing primary total knee arthroplasty were followed. Repeated-measures analysis of variance results indicated an effect of time on muscle strength, with all muscle groups being significantly weaker (knee extensors, P < 0.001; knee flexors, P < 0.001, ankle plantarflexors, P = 0.004; ankle dorsiflexors, P < 0.001) 1 mo postoperatively. Knee extensors were 42% weaker than preoperative levels, and knee flexors were 34% weaker, whereas the ankle plantarflexors were 17% weaker, and the dorsiflexors were 18% weaker. Three and 6 mos after surgery, strength in all muscle groups was similar to preoperative levels (P > 0.05 for all muscle groups). Patient function followed a similar trend, with patients walking slower 1 mo postoperatively (P < 0.001) and recovering to preoperative levels by 3 and 6 mos after surgery (P > 0.05).
CONCLUSIONS: Patients may benefit from early postoperative rehabilitation, including strengthening of the plantarflexors and dorsiflexors, although strengthening of the quadriceps and hamstrings muscles should continue to be a priority.