Knee biomechanics

BIOMECHANICAL DIFFERENCES OF DISSATISFIED TOTAL KNEE REPLACEMENT PATIENTS DURING STAIR DESCENT

Stair negotiation is one of the more difficult daily activities reported by total knee replacement (TKR) patients. Dissatisfied TKR patients have reported increased difficulty with stair negotiation, however it is unknown what the underlying mechanical issues are for this population. Therefore, the purpose of this research was to examine the knee joint biomechanics of dissatisfied TKR patients during stair descent. Nine dissatisfied TKR patients (34.6±14.3 months from surgery), 15 satisfied TKR patients (29.3±12.8 months from surgery), and 15 healthy participants performed stair descent trials on a five-step instrumented staircase at a preferred gait speed. The dissatisfied group showed lower knee extension and abduction moments in their replaced limb. The 2nd peak vertical ground reaction force (VGRF) and 1st and 2nd peak knee internal rotation moments showed lower moments for replaced limbs compared to non-replaced limbs. First peak VGRF was reduced for dissatisfied group compared to satisfied and healthy groups. The dissatisfied TKR group had significantly increased pain levels on their replaced limb compared to all other groups and limbs. The dissatisfied group had reduced gait speed compared to the satisfied and healthy groups. Increased pain levels lead to reduced descent speed and peak loading-response and pushoff sagittal plane knee joint moments in dissatisfied total knee replacement patients during stair descent. This creates an asymmetry in the extension loading response moment for the dissatisfied group, with the non-replaced limb showing increased joint moments whereas the satisfied and healthy groups do not have that imbalance.
Listed In: Biomechanics


Effects of Wide Step Width on Stair Ascent Knee Kinetics in Obese Participants

Purpose: An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moments. Increases in step width may act to reduce this moment. The purpose of this study was to determine the effects of increased step width on knee biomechanics during stair ascent of healthy-weight and obese participants. Methods: Participants ascended stairs while walking at their preferred speed in two different step width conditions – preferred and wide. A 2 x 2 (group x condition) mixed model analysis of variance (ANOVA) was performed to analyze differences between groups and conditions (p<0.05). Results: Increased step width decreased the loading-response peak vertical ground reaction force (GRF), loading-response knee abduction moment, knee extension ROM, and knee abduction ROM in both groups. However, it also increased loading and push-off peak mediolateral GRF, and peak knee abduction angle in both groups. Obese participants experienced a disproportionate increase in loading and push-off peak mediolateral GRF, and peak knee abduction angle compared to healthy. Conclusion: Increased SW successfully decreased loading-response peak knee abduction moment. Implications of this finding are that increased SW may decrease likelihood of developing medial compartment knee osteoarthritis. This study shows that this gait modification affects obese and healthy-weight differently, and the influence of body mass on knee biomechanics.


Listed In: Biomechanics


Hamstring Stiffness is Related to Anterior Tibial Translation when Transitioning from Non-weight Bearing to Weight Bearing

Anterior tibial translation (ATT) is shown to load the anterior cruciate ligament (ACL) as the knee transitions from non-weight bearing (NWB) to weight bearing (WB). Therefore, any factors able to effectively reduce ATT during initial WB would theoretically reduce ACL loading. This study evaluated the extent to which hamstring musculo-articular stiffness (KHAM) is associated with ATT as the knee transitions from NWB to WB in 10 healthy females (19.9 ± 1.5 yrs, 1.65 ± 0.06 m, 62.3 ± 6.3 kg). Linear regression revealed that KHAM predicted 48.6% of the variance in ATT (R^2 = .486, p = .025), with higher KHAM being associated with less ATT. KHAM is modifiable through training, and thus may be an important factor to consider from ACL injury prevention and rehabilitation perspectives.
Listed In: Biomechanics, Sports Science