The purposes of these studies were to determine differences in total (TCF), medial (MCF) and lateral (LCF) tibiofemoral compartment compressive forces and related muscle forces between limbs (replaced, non-replaced, and control), and different slopes during uphill [0° (level), 5°, 10°], and downhill [0° (level), 5° 10°] using statistical parametric mapping (SPM). Static optimization was used to determine muscle and compressive forces for 9 patients with total knee arthroplasty (TKA) and 9 control participants during walking trials. Total , loading-response, and push-off TCF impulse were calculated. A 3×3 [Limb (replaced, non-replaced, control] × Slope (0°, 10°, 15°)] SPM[F] repeated measures ANOVA was conducted independently for both uphill and downhill walking. Independent 3×3 (Limb × Slope]) mixed-model ANOVA were used to detect differences for TCF impulse for both up- and downhill walking.
For study one, significant between-limb differences were observed for MCF during 23-30% stance between replaced and control limbs. Significant differences between slopes were observed for all variables, except knee flexor muscle force. TCF impulse indicates that joint load is greater for all limbs as slope increases. A small sample size of patients with TKA who utilize different gait strategies may have rendered difference between limbs non-significant.
For study two, significant differences were found for TCF, MCF, and knee flexor muscle forces between replaced and control limbs during early loading-response (1‑5% stance). No significant differences were found between limbs for MCF or LCF, suggesting that TKA may have been successful in correcting errant frontal plane alignment. Loading-response TCF impulse increased with increasing slope yet push-off TCF impulse decreased with increasing decline slope suggesting decreased knee joint loading during push-off while not having to overcome gravity.
Uphill walking may be an effective exercise for high intensity early and long-term rehabilitation programs with increased muscular demand and quadriceps strengthening as slope increases while promoting the reacquisition of normal gait patterns following TKA. Downhill walking facilitates increased muscular demand and quadriceps strengthening via eccentric contractions while regaining normal gait patterns following TKA. Downhill walking, therefore, may be an effective exercise for high intensity early and long-term rehabilitation
