Comparison of mean knee flexor muscle forces during stair ascent for healthy controls and TKR patients.

<p>(A) short head of biceps femoris, (B) sartorius, (C) gracilis, (D) medial gastrocnemius, and (E) lateral gastrocnemius were computed using the computed muscle control (CMC) tool in OpenSim.</p

Early stance peak knee extensor and flexor muscle forces for healthy controls and TKR patients during stair ascent (Mean ± SD).

<p>Early stance peak knee extensor and flexor muscle forces for healthy controls and TKR patients during stair ascent (Mean ± SD).</p

Peak GRF, knee angle, knee moments, and knee JRF of healthy controls and TKR patients during stair climbing (Mean ± SD).

<p>Peak GRF, knee angle, knee moments, and knee JRF of healthy controls and TKR patients during stair climbing (Mean ± SD).</p

Inclusion and exclusion criteria for the TKR subjects.

<p>Inclusion and exclusion criteria for the TKR subjects.</p

Knee Joint Loads and Surrounding Muscle Forces during Stair Ascent in Patients with Total Knee Replacement

<div><p>Total knee replacement (TKR) is commonly used to correct end-stage knee osteoarthritis. Unfortunately, difficulty with stair climbing often persists and prolongs the challenges of TKR patents. Complete understanding of loading at the knee is of great interest in order to aid patient populations, implant manufacturers, rehabilitation, and future healthcare research. Musculoskeletal modeling and simulation approximates joint loading and corresponding muscle forces during a movement. The purpose of this study was to determine if knee joint loadings following TKR are recovered to the level of healthy individuals, and determine the differences in muscle forces causing those loadings. Data from five healthy and five TKR patients were selected for musculoskeletal simulation. Variables of interest included knee joint reaction forces (JRF) and the corresponding muscle forces. A paired samples t-test was used to detect differences between groups for each variable of interest (p<0.05). No differences were observed for peak joint compressive forces between groups. Some muscle force compensatory strategies appear to be present in both the loading and push-off phases. Evidence from knee extension moment and muscle forces during the loading response phase indicates the presence of deficits in TKR in quadriceps muscle force production during stair ascent. This result combined with greater flexor muscle forces resulted in similar compressive JRF during loading response between groups.</p></div

The 5-step (3 instrumented and 2 for turning around) staircase securely bolted to two force platforms for experimental data collection of ground reaction forces during stair negotiation.

<p>The 5-step (3 instrumented and 2 for turning around) staircase securely bolted to two force platforms for experimental data collection of ground reaction forces during stair negotiation.</p

Comparison of mean knee extensor muscle forces during stair ascent for healthy controls and TKR patients.

<p>(A) rectus femoris, (B) vastus medialis, (C) vastus lateralis, and (D) sum of knee extensors were computed using the computed muscle control (CMC) tool in OpenSim.</p

Late stance peak knee extensor and flexor muscle forces for healthy controls and TKR patients during stair climbing (Mean ± SD).

<p>Late stance peak knee extensor and flexor muscle forces for healthy controls and TKR patients during stair climbing (Mean ± SD).</p

Stair ascent velocity and functional assessments of healthy controls and TKR patients (Mean ± SD).

<p>Stair ascent velocity and functional assessments of healthy controls and TKR patients (Mean ± SD).</p

Comparison of mean knee joint reaction forces (JRF) during stair ascent for healthy controls and TKR patients.

<p>(A) shear and (B) compressive were computed using the joint reaction force (JRF) tool in OpenSim.</p