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  2. Physics of Living Systems

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

  1. Longfeng Rao
  2. Nils Horn
  3. Nadja Meister
  4. Stefan Preiss
  5. William R Taylor  Is a corresponding author
  6. Alessandro Santuz
  7. Pascal Schütz
  1. Laboratory for Movement Biomechanics, Institute for Biomechanics, Switzerland
  2. Department of lower extremities, Schulthess Clinic Zurich, Switzerland
  3. Max Delbrück Center for Molecular Medicine, Germany
https://doi.org/10.7554/eLife.85136
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  1. Longfeng Rao
  2. Nils Horn
  3. Nadja Meister
  4. Stefan Preiss
  5. William R Taylor
  6. Alessandro Santuz
  7. Pascal Schütz
(2023)
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
eLife 12:e85136.
https://doi.org/10.7554/eLife.85136
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4 figures, 5 tables and 4 additional files

Figures

Figure 1
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Tibiofemoral A-P translations in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right).

Means (solid lines) and standard deviation (shaded areas) of A-P translations in both groups are presented. Dotted colour lines indicate the mean toe-offs for the stable and unstable groups.

Figure 2
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Tibiofemoral rotations throughout a gait cycle in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right).

Means (solid lines) and standard deviations (shaded areas) of both groups are presented. Dotted lines indicate the mean toe-offs for each group.

Figure 3
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Mean and standard deviations (shaded) across subjects of the tibiofemoral A-P translations in the stable (8/8, blue), and unstable (5/8, orange) groups without reported instability during the measured activities.

In addition, mean and standard deviations (shaded) across trials of three individuals from the unstable group who reported instability during the measured activities are shown in red. Dashed colour lines indicate the mean toe-offs for the stable and unstable groups, as well as for each unstable total knee arthroplasty (TKA) knee with specifically reporting instability.

Figure 4
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Classified muscle synergies in both stable and unstable total knee arthroplasty (TKA) knees during level walking, downhill walking, and stair descent.

Muscle synergy weights, as well as means (solid lines) and standard deviations (shaded areas) of the corresponding time/amplitude-normalized activation patterns are presented for each activity. RF: rectus femoris, VM: vastus medialis, VL: vastus lateralis, TA: tibialis anterior, HM: medial hamstrings, HL: lateral hamstrings, GM: gastrocnemius medialis, GL: gastrocnemius lateralis.

Tables

Table 1
Clinical assessment data of the stable and unstable groups shown as mean ± standard deviation of each parameter.

BMI: body mass index; PTS: posterior tibial slope; RoM: range of motion; OKS: Oxford Knee Score; COMI-Knee: Core Outcome Measures Index-Knee; EQ-VAS: EQ-Visual Analogue Scales. Bold values indicate a significant difference.

Baseline dataStable (N = 10)Unstable (N = 8)p
Sex ratio7M:3F3M:5F0.168
Age [years]62.6 ± 6.868.9 ± 8.30.096
BMI [kg/m2]29.4 ± 4.826.1 ± 3.20.113
Time post-op [months]33.9 ± 8.531.9 ± 20.40.779
PTS [°]82.0 ± 2.482.3 ± 3.00.863
Inlay thickness [mm]11.3 ± 1.011.8 ± 1.70.511
Knee flexion RoM [°]125.0 ± 7.8126.3 ± 6.40.720
Hyperextension1/108/8<0.01
Drawer tests1/105/80.019
Varus/valgus stress tests1/105/80.019
UCLA activity score8.3 ± 1.37.9 ± 1.10.465
OKS46.0 ± 2.042.9 ± 3.80.040
COMI-Knee0.2 ± 0.60.9 ± 0.80.044
EQ-VAS84.5 ± 13.481.3 ± 17.10.660
Table 2
Mean ± standard deviation of the anterior-posterior(A-P) tibiofemoral positions for the medial and lateral condyles, flexion/extension (Flex/ex), adduction/abduction (Ab/ad), and internal/external (Int/ext) rotation angles in stable and unstable groups during all activities.
A-P translation RoM [mm]Stance phaseSwing phase
MedialLateralDiffMedialLateralDiff
Level walkingStable5.4 ± 1.45.1 ± 1.0−0.3 ± 2.27.0 ± 2.55.7 ± 1.9−1.1 ± 1.5
Unstable4.5 ± 0.94.5 ± 0.8−0.3 ± 1.86.2 ± 1.65.5 ± 1.5−0.6 ± 2.1
Downhill walkingStable4.2 ± 0.94.0 ± 0.7−0.2 ± 1.05.7 ± 1.54.7 ± 1.2−1.0 ± 1.6
Unstable3.4 ± 1.04.5 ± 0.71.1 ± 1.35.5 ± 1.55.4 ± 2.0−0.1 ± 1.6
Stair descentStable5.1 ± 1.65.5 ± 1.90.4 ± 0.87.7 ± 1.76.0 ± 2.1−1.7 ± 2.0
Unstable4.6 ± 1.25.5 ± 1.70.9 ± 0.86.9 ± 1.77.4 ± 2.90.5 ± 2.4
Table 3
Mean ± standard deviation of knee range of flexion/extension (flex/ex), abduction/adduction (ab/ad), and internal/external (int/ext) rotations for the stance and swing phases of level walking, downhill walking, and stair descent.

A significant difference was observed only between stable and unstable groups in abduction/adduction during downhill walking (a).

Rotation RoM [°]Stance phaseSwing phase
flex/exint/extab/adflex/exint/extab/ad
Level walkingStable47.2 ± 4.97.7 ± 1.12.1 ± 0.261.8 ± 4.46.9 ± 1.82.8 ± 0.5
Unstable43.5 ± 6.87.0 ± 1.82.1 ± 0.359.6 ± 8.07.8 ± 2.52.7 ± 0.7
Downhill walkingStable57.9 ± 3.85.5 ± 0.92.2 ± 0.3a68.6 ± 4.67.0 ± 1.32.5 ± 0.4
Unstable54.9 ± 4.36.1 ± 1.22.8 ± 0.3a67.4 ± 6.78.2 ± 1.82.8 ± 0.7
Stair descentStable84.4 ± 3.48.7 ± 1.23.5 ± 0.591.2 ± 4.59.4 ± 1.92.8 ± 0.6
Unstable84.5 ± 11.78.4 ± 1.03.3 ± 0.492.8 ± 5.810.3 ± 2.63.1 ± 0.9
Table 4
Mean ± standard deviation of full width at half maximum (FWHM) of the synergistic activation patterns corresponding to knee extensor, plantarflexor, dorsiflexor, and knee flexor muscle groups during level walking, downhill walking, and stair descent.

Significant differences were observed between stable and unstable knees during stair descent in dorsi- (a) and knee flexor muscles (b), with an effect size of 1.49. *The classified synergy corresponding to dorsi- and knee flexor muscles was only observed in a small number of unstable knees (3/8).

FWHMKnee extensorsPlantarflexorsDorsiflexorsKnee flexors
StableUnstablepStableUnstablepStableUnstablepStableUnstablep
Level walking29.3 ± 8.128.6 ± 13.10.5524.3 ± 7.925.5 ± 6.70.3837.4 ± 13.227.7 ± 8.30.11*21.7 ± 6.230.4 ± 9.50.06
Downhill walking31.2 ± 9.434.1 ± 6.60.2620.2 ± 7.322.6 ± 8.40.2935.2 ± 15.931.1 ± 13.20.3220.2 ± 5.721.6 ± 5.50.37*
Stair descent31.8 ± 12.236.0 ± 7.30.2026.0 ± 9.433.5 ± 15.10.1220.1 ± 8.135.0 ± 12.50.01a20.1 ± 8.135.0 ± 12.50.01b
Table 5
Mean ± standard deviation of centre of activity (CoA) of the synergistic activation patterns corresponding to knee extensor, plantarflexor, dorsiflexor, and knee flexor muscle groups during level walking, downhill walking, and stair descent.

A significant difference was observed between stable and unstable knees during stair descent in dorsiflexor muscles (a), with an effect size of 2.17. *The classified synergy corresponding to dorsi- and knee flexor muscles was only observed in a small number of unstable knees (3/8).

CoAKnee extensorsPlantarflexorsDorsiflexorsKnee flexors
StableUnstablepStableUnstablepStableUnstablepStableUnstablep
Level walking31.8 ± 11.734.6 ± 23.20.3960.5 ± 6.457.1 ± 8.50.81141.4 ± 37.368 ± 22.70.004a*34.7 ± 22.969.8 ± 78.80.19
Downhill walking35.6 ± 6.732.6 ± 8.40.7745.8 ± 10.446.4 ± 9.30.46119.8 ± 46.798.3 ± 51.80.2386.5 ± 39.8108.1 ± 30.10.19*
Stair descent41.2 ± 8.041.4 ± 9.40.49157.3 ± 27.3172.4 ± 29.60.1661.9 ± 24.968 ± 26.20.3361.9 ± 24.968 ± 26.20.33

Additional files

Supplementary file 1

Mean ± standard deviation of kinematic parameters of interest in stable and unstable groups at the instant of heel-strike in all activities.

https://cdn.elifesciences.org/articles/85136/elife-85136-supp1-v2.docx
Supplementary file 2

Post hoc pair-wise comparisons of one-way analysis of variance (ANOVA) results on hamstrings-dominant classified synergy module during stair descent.

Bold values indicate the comparison of the same muscle between stable and unstable groups. RF: rectus femoris, VM: vastus medial, VL: vastus lateral, TA: tibialis anterior, HM: hamstrings medial, HL: hamstring lateral, GM: gastrocnemius medial, GL: gastrocnemius lateral.

https://cdn.elifesciences.org/articles/85136/elife-85136-supp2-v2.docx
MDAR checklist
https://cdn.elifesciences.org/articles/85136/elife-85136-mdarchecklist1-v2.pdf
Reporting standard 1

Strobe checklist.

https://cdn.elifesciences.org/articles/85136/elife-85136-repstand1-v2.pdf

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  1. Longfeng Rao
  2. Nils Horn
  3. Nadja Meister
  4. Stefan Preiss
  5. William R Taylor
  6. Alessandro Santuz
  7. Pascal Schütz
(2023)
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
eLife 12:e85136.
https://doi.org/10.7554/eLife.85136