Tibiofemoral compressive force during downhill walking in patients with primary total knee arthroplasty: A statistical parametric mapping approach

Background: Downhill walking is a necessary part of daily life and an effective activity in post-operative reha-bilitation following total knee arthroplasty. The purpose of this study was to determine differences in the behavior of total, medial, and lateral tibiofemoral compressive forces as well as knee extensor and flexor muscle forces between different limbs of patients with total knee arthroplasty (replaced, non-replaced) during downhill and level walking. Methods: Musculoskeletal modeling and simulation were implemented to determine muscle forces and tibiofe-moral compressive forces in 25 patients with total knee arthroplasty. A 2 x 2 [Limb (replaced, non-replaced) x Slope (0 degrees, 10 degrees)] Statistical parametric mapping repeated measures analysis of variance was conducted on selected variables. Findings: Statistical parametric mapping did not identify any between-limb differences for compressive or muscle forces. Differences in joint compressive and muscle forces persisted throughout different intervals of stance-phase between level and downhill walking. Knee extensor muscle forces were distinctly greater during level walking for nearly all of stance phase. Knee flexor muscle force was greater during downhill walking for >60% of stance. Statistical parametric mapping did identify regions of significance between level and downhill walking that coincided temporally (near loading response and push off) with peak joint moment and joint compressive forces traditionally reported using discrete variable analyses. Interpretation: Downhill walking may be a safe and useful rehabilitation tool for post-knee arthroplasty reha-bilitation that will not disproportionally load either the replaced or the non-replaced joint and where the quadriceps muscles can be strengthened during a gait-specific task.