Comparable in vivo joint kinematics between self-reported stable and unstable knees after TKA can be explained by muscular adaptation strategies: A retrospective observational study
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eLife assessment
This manuscript provides valuable data gathered using a new video fluoroscopy method by which movements of artificial joints can be visualized in real time. These solid data add to the understanding of the links between symptoms of unstable joints after total knee replacement and actual joint instability. The paper should be of interest to those who study biomechanics after total joint replacement.
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Abstract
Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to total knee arthroplasty (TKA) revision. Nevertheless, subjective knee instability is not well defined clinically, plausibly because the relationships between instability and implant kinematics during functional activities of daily living remain unclear. Although muscles play a critical role in supporting the dynamic stability of the knee joint, the influence of joint instability on muscle synergy patterns is poorly understood. Therefore, this study aimed to understand the impact of self-reported joint instability on tibiofemoral kinematics and muscle synergy patterns after TKA during functional gait activities of daily living.
Methods:
Tibiofemoral kinematics and muscle synergy patterns were examined during level walking, downhill walking, and stair descent in eight self-reported unstable knees after TKA (3M:5F, 68.9 ± 8.3 years, body mass index [BMI] 26.1 ± 3.2 kg/m 2 , 31.9 ± 20.4 months postoperatively), and compared against 10 stable TKA knees (7M:3F, 62.6 ± 6.8 years, 33.9 ± 8.5 months postoperatively, BMI 29.4 ± 4.8 kg/m 2 ). For each knee joint, clinical assessments of postoperative outcome were performed, while joint kinematics were evaluated using moving video-fluoroscopy, and muscle synergy patterns were recorded using electromyography.
Results:
Our results reveal that average condylar A-P translations, rotations, as well as their ranges of motion were comparable between stable and unstable groups. However, the unstable group exhibited more heterogeneous muscle synergy patterns and prolonged activation of knee flexors compared to the stable group. In addition, subjects who reported instability events during measurement showed distinct, subject-specific tibiofemoral kinematic patterns in the early/mid-swing phase of gait.
Conclusions:
Our findings suggest that accurate movement analysis is sensitive for detecting acute instability events, but might be less robust in identifying general joint instability. Conversely, muscle synergy patterns seem to be able to identify muscular adaptation associated with underlying chronic knee instability.
Funding:
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Article activity feed
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eLife assessment
This manuscript provides valuable data gathered using a new video fluoroscopy method by which movements of artificial joints can be visualized in real time. These solid data add to the understanding of the links between symptoms of unstable joints after total knee replacement and actual joint instability. The paper should be of interest to those who study biomechanics after total joint replacement.
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Reviewer #1 (Public Review):
This manuscript seeks a greater understanding of joint movements in recipients of total knee replacements who have symptoms of unstable prosthetic joints. The authors describe the results of a carefully conducted retrospective analysis of joint movements after total knee replacement (TKA) using a recently developed method based on videofluoroscopy. Kinematic data supplemented by electromyography measurements of muscle activation through normal gait. These measurements were conducted while walking on flat ground, down an incline, or down stairs. The kinematics and EMG data provide convincing evidence of altered knee kinematics when symptoms of joint instability occurred that were accompanied by subject-specific changes in patterns of muscle activation. The manuscript raises interesting questions about how …
Reviewer #1 (Public Review):
This manuscript seeks a greater understanding of joint movements in recipients of total knee replacements who have symptoms of unstable prosthetic joints. The authors describe the results of a carefully conducted retrospective analysis of joint movements after total knee replacement (TKA) using a recently developed method based on videofluoroscopy. Kinematic data supplemented by electromyography measurements of muscle activation through normal gait. These measurements were conducted while walking on flat ground, down an incline, or down stairs. The kinematics and EMG data provide convincing evidence of altered knee kinematics when symptoms of joint instability occurred that were accompanied by subject-specific changes in patterns of muscle activation. The manuscript raises interesting questions about how patients adapt muscle activation patterns to limit discomfort prior to TKA and to what degree these same defensive strategies influence joint stability post-operatively.
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Reviewer #2 (Public Review):
The authors report a study comparing self-reported stable and unstable knees with total knee arthroplasty. Advanced imaging methods (dynamic fluoroscopy with model-image registration) and analysis of muscle activities were used to characterize the study subjects during three ambulatory activities (level gait, downhill walking, and stair descent).
The subject cohort all received one design of TKA in a similar time period. The unstable subgroup was >60% female, while the stable knee cohort was 70% male, which is a notable limitation. The measurement methods are state-of-the-art and expertly applied.
The results suggest there may be measurable differences in knee kinematics in subjects with unstable knees, but this was not strongly supported across groups. Rather it was highlighted in 3 individuals who …
Reviewer #2 (Public Review):
The authors report a study comparing self-reported stable and unstable knees with total knee arthroplasty. Advanced imaging methods (dynamic fluoroscopy with model-image registration) and analysis of muscle activities were used to characterize the study subjects during three ambulatory activities (level gait, downhill walking, and stair descent).
The subject cohort all received one design of TKA in a similar time period. The unstable subgroup was >60% female, while the stable knee cohort was 70% male, which is a notable limitation. The measurement methods are state-of-the-art and expertly applied.
The results suggest there may be measurable differences in knee kinematics in subjects with unstable knees, but this was not strongly supported across groups. Rather it was highlighted in 3 individuals who self-reported instability during the test session. The muscle activity analysis supports there being differences between the stable and unstable knee groups.
Despite the limitations of a small subject cohort with only a single TKA design, the study highlights important methods that appear suitable to further study the factors contributing to clinical dissatisfaction with TKA as it relates to joint stability and function during ambulatory tasks.
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