LAUSR

Background National joint replacement registries have reported a substantial growth in younger knee osteoarthritic patients (< 55 years old) undergoing total knee replacement, however this younger population is generally understudied. Importantly, studies examining experimentally controlled perturbation have shown age‐related differences between younger and older healthy adults, whether similar age‐related differences exist among total knee replacement patients is unknown. Methods A total of 59 participants, including 29 unilateral total knee replacement patients (six‐months post‐surgery) made up the four experimental groups: 1) younger patient (54.3 (SD 7.9) years), 2) younger control (55.2 (SD 4.0) years), 3) older patient (76.9 (SD 4.7) years), and 4) older control (77.7 (SD 4.1) years). Using a tether‐release method to perturb balance and simulate a forward fall, center of mass and stepping characteristics were analyzed. Findings Younger patients recovered following the perturbation with a significantly smaller center of mass displacement compared to the older patients (14.85 (SD 0.01) v. 18.13 (SD 0.02) %ht, p = 0.02); utilizing a longer (0.43 (SD 0.02) v. 0.39 (SD 0.03) m, p < 0.001) and higher velocity (2.01 (SD 0.2) v. 1.59 (SD 0.2) m/s, p = 0.001) recovery step. Importantly, younger patients did not differ significantly from the younger controls in center of mass displacement or recovery step characteristics (p > 0.05). Interpretation The younger patients demonstrated superior center of mass control in response to a forward perturbation, suggesting that younger patients would be at a reduced risk of falling when recovering from a forward‐directed postural perturbation compared to older patients. HighlightsReports show a rise in younger patients undergoing total knee replacement surgery.Currently, little is known regarding the function and mobility of the younger patient.A tether‐release method to perturb balance was used to simulate a forward fall.Younger patients achieve superior center of mass control compared to older patients.Recovering from a forward perturbation younger patients are at a reduced fall risk.