Author(s): IZADI, M., TØIEN, T., ØHRN, F.D., SCHNELL HUSBY, O., KVITLAND SCHNELL HUSBY, V., BJØRGEN WINTHER, S., SHERMAN, R., FORSBERG BROBAKKEN, M., WANG, E., BERG, O.K., Institution: MOLDE UNIVERSITY COLLEGE, Country: NORWAY, Abstract-ID: 1012

INTRODUCTION:
Despite a high surgical success rate, total knee arthroplasty often results in a profound and debilitating decline in physical function. Although lower-limb muscle strength is a strong predictor of physical function in patients with advanced knee osteoarthritis prior to surgery, its prognostic value for postoperative function following total knee arthroplasty remains unclear.
METHODS:
Hierarchical linear regression analyses were conducted to examine the predictive value of pre-operative leg press maximal strength relative to body weight for post-operative physical function in 40 total knee arthroplasty patients (age: 66 ± 7 years; 17 males and 23 females; and BMI: 29 ± 5 kg/m²). Outcome variables were postoperative performance-based physical function tasks, including 10-step stair climbing, 30 s sit-to-stand, 40 m fast-paced walking, and unipedal stance tests at 3 weeks postoperatively. Sit-to-stand and stair climbing were also assessed at the 1-year follow-up, and separate regression models were conducted for each time point. For each variable, age, sex, and post-operative pain assessed at the corresponding follow-up time point were entered in the first block as covariates, and maximal strength was added in the second block as the predictor.
RESULTS:
The model with covariates was only associated with balance at 3 weeks and only stair climbing at the 1-year follow-up. The addition of maximal strength significantly improved prediction of function. At 3 weeks postoperatively, maximal strength was a strong predictor of sit-to-stand (p < 0.001), stair climbing (p < 0.001), and balance performance (p = 0.004), accounting for 40%, 36%, and 18% of the variance, respectively. Maximal strength was not significantly associated with fast-paced walking. The predictive ability of maximal strength for sit-to-stand (p = 0.002; 26%) and stair climbing (p = 0.012; 11%) persisted at 1 year.
CONCLUSION:
Preoperative maximal strength is a powerful predictor of physical function at early- and mid-term follow-up after total knee arthroplasty, particularly for force-driven tasks such as sit-to-stand and stair climbing. It provides prognostic information and may help identify patients at risk of poorer early- and mid-term postoperative physical function, supporting optimized interventions to target preoperative lower limb maximal strength.