Does hamstrings co-contraction constrain knee internal rotation in patients with knee endoprosthesis during decline slope walking?

BACKGROUND: Medial and lateral hamstrings are known for their capacity to promote internal or external rotation of the knee. Apart from implant geometry, increased co-contraction to a larger share of either the medial or lateral hamstrings has the potential to contribute to the restricted knee internal rotation especially under consideration of cruciate ligament substituting compared to cruciate ligament retaining knee endoprosthesis designs. Hence, the purpose of the study was to evaluate, whether increased co-contraction of the hamstrings contribute to the impaired knee internal rotation in total and unicondylar knee arthroplasty patients during level and decline walking. METHODS: Knee joint angles were calculated using an inverse kinematics model in Anybody. Muscle activity was examined of the semitendinosus and biceps femoris. FINDINGS: Knee internal rotation was constraint in the operated compared to the non-operated limb only in the total knee arthroplasty group during decline slope walking. Co-contraction values revealed no statistically significant differences between the operated and non-operated limb during the limited knee internal rotation period of time (59-94% of stance). Biceps femoris activity was significantly reduced (69-71% of stance) in the operated limb in the total knee arthroplasty group during decline slope walking. INTERPRETATION: Contrary to the proposed mechanism, aspects other than co-contraction between semitendinosus and biceps femoris are involved in the impaired transverse plane knee motion. These include implant congruency and probably friction. Unexpectedly, the biceps femoris did not compensate the absence of the anterior cruciate ligament with increased muscular activity in the operated limb of the total knee arthroplasty group.

Compromised knee internal rotation in total knee arthroplasty patients during stair climbing.

Due to the significant role of rotational properties for normal knee function, this study aimed to investigate transverse plane kinematics and kinetics in total knee arthroplasty and unicondylar knee arthroplasty patients during activities of daily living compared to a healthy control group, including stair ascent and descent. The study participants consisted of a total knee arthroplasty group including posterior cruciate retaining and posterior stabilized designs as well as a unicondylar knee arthroplasty group and a healthy control group. Three-dimensional kinematics and kinetics were captured using a Vicon system and two Kistler force plates embedded in the floor and another two in a staircase. Inverse dynamics of the lower limbs was computed in Anybody™ Modeling System. Transverse plane joint angles and joint moments were analyzed utilizing the statistical non-parametric mapping approach, considering the entire curve shape for statistical analysis. The patients with total knee arthroplasty exhibited significantly reduced knee internal rotation of the operated knee compared to the control group and the patients' unimpaired limb, especially during the stair climbing tasks. Both unicondylar and total knee arthroplasty patients were found to have similar reduced internal rotation motion time series in stair descent. In conclusion, potential kinematic and kinetic benefits of unicondylar knee arthroplasty over total knee arthroplasty could not be proven in the current study. Aside from the usually mentioned reasons inducing constrained knee internal rotation in total knee arthroplasty patients, future studies should investigate to what extent co-contraction may contribute to this functional impairment in patients after knee arthroplasty surgery.