Background: Gait adaptability is of utmost importance for keeping balance during gait in patients with knee osteoarthritis, also after total knee arthroplasty (TKA). The aims of this explorative study are: (1) assess the effect of age, knee osteoarthritis and TKA on gait adaptability; (2) assess changes in gait adaptability pre-to post-TKA and (3) their relation to functional outcomes. Methods: Gait adaptability was measured using a Target Stepping Test (TST) in knee osteoarthritis patients before (preTKA) and 12 months after TKA (postTKA) and compared to asymptomatic old (AsOld) and young adults (AsYng). TST imposed an asymmetrical gait pattern with projected stepping targets at high walking speed. Gait adaptability was determined through stepping accuracy on the targets. The Oxford Knee Score (OKS) and Timed-Up-and-Go test (TUG) measured patients’ physical function. Results: 12 preTKA, 8 postTKA, 18 AsYng, 21 AsOld were tested. Age showed no effect on TST-stepping accuracy. PreTKA showed worse TST-stepping accuracy compared to AsYng and AsOld (7.7; 6.2 cm difference). PostTKA showed an improvement of 52% in TST-stepping accuracy compared to preTKA (3.2 cm). Higher stepping accuracy preTKA predicted higher stepping accuracy post-TKA. In addition, low preTKA stepping accuracy predicted more improvement postTKA. Pre-to post-TKA improvement of stepping accuracy was related to improvement on the TUG (Beta = 0.17, p = 0.024), but not to OKS. Conclusions: Gait adaptability is improved following TKA in knee osteoarthritis patients and no longer significantly worse than asymptomatic adults. The relation of gait adaptability to function is shown by its relation to the TUG and shows to have predictive value pre-to post-TKA.

Background: The assessment of functional recovery of patients after a total knee replacement includes the quantification of gait deviations. Comparisons to comfortable gait of healthy controls may incorrectly suggest biomechanical gait deviations, since the usually lower walking speed of patients already causes biomechanical differences. Moreover, taking peak values as parameter might not be sensitive to actual differences. Therefore, this study investigates the effect of matching walking speed and full-waveform versus discrete analyses. Methods: Gait biomechanics of 25 knee replacement patients were compared to 22 controls in two ways: uncorrected and corrected for walking speed employing principal component analyses, to reconstruct control gait biomechanics at walking speeds matched to the patients. Ankle, knee and hip kinematics and kinetics were compared over the full gait cycle using statistical parametric mapping against using peak values. Findings: All joint kinematics and kinetics gait data were impacted by applying walking speed correction, especially the kinetics of the knee. The lower control walking speeds used for reference generally reduced the magnitude of differences between patient and control gait, however some were enlarged. Full-waveform analysis identified greater deviating gait cycle regions beyond the peaks, but did not make peak value analyses redundant. Interpretation: Matching walking speed of controls affects identification of gait deviations in patients with a total knee replacement, reducing deviations confounded by walking speed and revealing hidden gait deviations related to possible compensations. Full-waveform analysis should be used along peak values for a comprehensive quantification of differences in gait biomechanics.

Background: After total knee replacement (TKR) some patients report low self-perceived function, which is clinically measured using patient reported outcome measures (PROMs). However, PROMs, e.g. the Oxford Knee Score (OKS), inherently lack objective parameters of knee function. Biomechanical gait analysis is an objective and reliable measurement to quantitatively assess joint function. Therefore, the aim of this study was to explore the relationship between biomechanical gait parameters and the OKS. Methods: Gait analyses were recorded in 37 patients at least one year after primary TKR and in 24 healthy controls. Parameters from this analysis were calculated for hip, knee and ankle joint angles and joint moments in the sagittal and frontal plane including initial contact, early, late stance and swing. For the patients these parameters were expressed as its difference to control values at matched walking speed. Linear regression analyses were performed between the parameters from gait analysis and the OKS, with speed as covariate. Results: The difference in knee extension angle at initial contact and late stance between patients and controls was significantly related to the OKS. Per one degree knee extension difference increase, the OKS reduced with 1.0 to 1.6 points. Overall, patients extended their knee less than controls. Neither ankle and hip gait parameters, nor joint moments showed a relation with OKS. Conclusions: All patients with a submaximal score on the OKS showed limited knee extension during gait, even without a mechanical constraint in knee extension. This could be related to motor control limitations in this patient group.

Objective: To evaluate muscle activation patterns and co-contraction around the knee in response to walking with modified gait patterns in patients with medial compartment knee-osteoarthritis (KOA). Design: 40 medial KOA patients walked on an instrumented treadmill. Surface EMG activity from seven knee-spanning muscles (gastrocnemius, hamstrings, quadriceps), kinematics, and ground reaction forces were recorded. Patients received real-time visual feedback on target kinematics to modify their gait pattern towards three different gait modifications: Toe-in, Wider steps, Medial Thrust. The individualized feedback aimed to reduce their first peak knee adduction moment (KAM) by ≥ 10%. Changes in muscle activations and medial/lateral co-contraction index during the loading response phase (10–35% of the gait cycle) were evaluated, for the steps in which ≥ 10% KAM reduction was achieved. Results: Data from 30 patients were included in the analyses; i.e. all who could successfully reduce their KAM in a sufficient number of steps by ≥ 10%. When walking with ≥ 10% KAM reduction, Medial Thrust gait (KAM − 31%) showed increased flexor activation (24%), co-contraction (17%) and knee flexion moment (35%). Isolated wider-step gait also reduced the KAM (− 26%), but to a smaller extent, but without increasing muscle activation amplitudes and co-contraction. Toe-in gait showed the greatest reduction in the KAM (− 35%), but was accompanied by an increased flexor activation of 42% and hence an increased co-contraction index. Conclusion: Gait modifications that are most effective in reducing the KAM also yield an increase in co-contraction, thereby compromising at least part of the effects on net knee load.