Weight-bearing asymmetry during sit-stand transitions related to impairment and functional mobility after total knee arthroplasty.

OBJECTIVES: To examine changes in weight-bearing (WB) asymmetry during sit-stand transitions for individuals during the first 6 months after unilateral total knee arthroplasty (TKA). Relationships between WB asymmetry, clinical measures of knee impairment, and functional mobility also were evaluated.
DESIGN: Prospective repeated-measures design.
SETTING: Clinical research laboratory. PARTICIPANTS: People (N=36) with knee osteoarthritis (OA) scheduled to undergo unilateral TKA and a control (CTL) group (N=17 healthy people) were enrolled. INTERVENTION: The TKA group participated in acute, home, and outpatient phases of exercise-based rehabilitation. MAIN OUTCOME MEASURES: WB asymmetry measured during a 5-Times Sit-to-Stand Test (FTSST) based on average vertical ground reaction force under each foot, self-reported knee pain using a numerical pain rating scale, knee active range of motion symmetry, knee extensor strength symmetry, FTSST time, 6-minute walk test distance, and Stair Climbing Test time.
RESULTS: Compared with preoperative values, the TKA group showed greater WB asymmetry at 1 month after surgery (P<.001). By 6 months, the TKA group had less WB asymmetry than preoperative values (P<.001), which was not different from the CTL group. Symmetry in WB correlated with functional outcomes and symmetry of quadriceps strength for the TKA group 6 months postoperatively.
CONCLUSIONS: Patients with unilateral knee OA showed WB asymmetry during sit-stand transitions early after unilateral TKA that improved by 6 months after surgery and was no different from that for healthy people of similar age. For people in the first 6 months after TKA, greater symmetry was related to better function and strength symmetry.