An evaluation of knee adduction moment, varus thrust, and ground reaction force before and after total knee arthroplasty in osteoarthritic knee patients

Abstract

Frontal plane gait deviations have been identified as important factors for the progression of knee osteoarthritis (OA), especially in the medial compartment. External knee adduction moment (KAM), varus thrust, and ground reaction forces (GRF) within the osteoarthritic population were examined before and after total knee arthroplasty (TKA). Ten adult volunteers preparing to undergo TKA were recruited and a control group consisting of 11 volunteers from the community. A longitudinal repeated measures design was conducted prior to TKA and three weeks, six weeks, three months and six months post-surgery. External KAM in OA patients reduced after surgery, however, progressively increased over time, approaching baseline numbers at six months. Varus thrust increased overtime reaching numbers double baseline values in OA patients. The GRF was lower in the knee OA patients compared to controls and remained decreased throughout study. While walking velocity may be a factor in GRF and thereby KAM, the increase cannot fully explain the increase in KAM after surgery. Weak knee stabilizers and altered gait mechanics could potentially explain the continued increase in varus thrust. Also, static alignment and joint instability may be an integral part to the increases of KAM and varus thrust that needs to be studied more thoroughly. Further research on strengthening and gait retraining protocols following TKA, may help to better understand these biomechanical factors and their effect on the progression of knee OA. Key Words: Osteoarthritis, knee, frontal gait biomechanics, total knee arthroplasty, external knee adduction moment, varus thrust, ground reaction forces.