Fig. 1

Regression model with spline. Relationship between post-total knee arthroplasty (TKA) range of motion (ROM) at final follow-up and contralateral ROM of <115° and ≥115°. Dark blue line: LOESS curve illustration of relationship between contralateral ROM and post-TKA ROM at final follow-up. Light blue line: reference line where contralateral ROM is perfectly predictive of post-TKA ROM at final follow-up