1. Dynamic Knee Stability and Perturbation Training

2. Dynamic Knee Stability Rudolph et al, KSSTA 2001 31 active subjects –10 uninjured –11 copers –10 non-copers Screening evaluation Quadriceps strength testing Knee joint laxity testing

3. Testing EMG testing –Normalized to maximum EMG –Variables Muscle onset (threshold 2.5x ave rest EMG) Termination of activity Magnitude (Integration over weight acceptance interval) Co-contraction of VL-LH, VL-MG

4. Testing 3D motion analysis –Self-selected walking, jogging speeds –Joint motions, moments –Support moments

5. Walking CoperNon-coperControl InvolvedUninvolvedInvolvedUninvolvedInvolvedUninvolved Vert GRF at loading (F=8.499, P=0.017)* 1.25%BW (±0.030) 1.23%BW (±0.022) 1.22%BW (±0.031) 1.26%BW (±0.033) 1.31%BW* (±0.031) 1.29%BW* (±0.033) Peak knee flexion angle (negative=flexion) (F=8.499, P=0.017)** -22.8° (±1.9) -24.5° (±1.8) -21.9°** (±1.9) -25.9° (±1.9) -26.5° (±1.9) Knee moment at PKF (F=6.212, P=0.034)** 0.368 (±0.07) 0.437 (±0.68) 0.314** (±0.071) 0.542 (±0.071) 0.558 (±0.074) 0.601 (±0.071) Soleus integral over wt acceptance (t=2.894, P=0.020)** 8.655 (±1.292) 7.489 (±0.679) 9.811** (±1.362) 6.626 (±0.716) 8.302 (±1.292) 7.612 (±0.679) *Control group different from copers and non-copers (P<0.05) **Non-copers' involved side different from all others (P<0.05)

6. Walking Distribution of support moments on the involved side during weight acceptance, walking. Non-copers* had lower knee moments (F=5.402, P=0.045) and higher hip moments (F=3.979, P=0.056) than copers or uninjured subjects

7. Walking Knee flexion angle External knee flexion moment Quadriceps index Copers r=0.029, P=0.932r=0.135, P=0.693 Non-copers r=0.933, P=0.000*r=0.716, P=0.030* Lateral hamstrings Onset- to-peak EMG Copers r=0.672, P=0.030*r=0.765, P=0.010* Non-copers r=0.095, P=0.824r=0.408, P=0.316 Non-coperCoper Quadriceps strength (t=4.033, P=0.001)* 75.3% (±11%)97.1% (±12.7%)

8. Walking Regression analyses –79.5% of the variability in the knee moment at peak knee flexion accounted for by the variability in the onset-to-peak of the hamstrings and quadriceps muscles (F=6.009, P=0.030) in the copers only.

9. Jogging CopersNon-copersControls InvolvedUn-involvedInvolvedUn-involvedInvolvedUn-involved Velocity m/s per LL (F=4.00, P=0.03)* 4.041 (±0.23) 4.00 (±0.19) 4.137 (±0.24) 4.236 (±0.21) 4.745* (±0.23) 4.885* (±0.19) Stride length m/LL (F=4.30, P=0.029)* 3.089 (±0.13) 3.034 (±0.11) 3.194 (±0.18) 3.297 (±0.15) 3.575* (±0.15) 3.592* (±0.13) Vertical ground reaction force (F=2.849, P=0.075) 2.172 (±0.07) 2.204 (±0.07) 2.084 (±0.07) 2.156 (±0.07) 2.322 (±0.07) 2.357 (±0.07)

10. Jogging Knee flexionKnee moment

11. Jogging Non-copers had significantly greater hip (F=3.3994, P=0.030) and less knee (F=4.727, P=0.017) extensor moments on the involved sides

12. Jogging Non-copers had significantly greater co- contraction between vastus lateralis and medial gastrocnemius in the involved limb (*F=3.609, P=0.041) Peak knee flexion angle Knee moment at peak knee flexion Passive laxity Copers NS r=0.203, P=1.000 Non-copers NS r=-0.866, P=0.015* Quadriceps index Copers NS r=-0.133, P=1.000 Non-copers NS r=-0.798, P=0.060** VL-LH co- contraction Copers NS r=-0.417, P=0.231 Non-copers NS r=-0.670, P=0.048*

13. Jogging Regression analyses –83.5% of the variability in the knee moment at peak knee flexion accounted for by the variability in the amount of VL-LH and VL- MG co-contraction (F=15.231, P=0.004) in the non-copers only.

14. Conclusions COPERSNON-COPERS Normal knee motions and moments Less co-activation Muscle activation- important factor in stability Compensation related to quadriceps strength, passive knee laxity Reduced knee flexor moment Reduced knee motion Transfer control to hip Possible delayed force production?

15. Perturbation training Fitzgerald et al, PT 2000 26 subjects completed training –14 subjects in standard group –12 subjects in perturbation group Screening exam –Pass “rehab candidate” criteria

16. Training programs STANDARD PROGRAM PERTURBATION TRAINING Resistance training to quads and hams Cardiovascular endurance training Agility training Sport-specific skill training AP, ML on Balance Master AP, ML rotary on tiltboard Rollerboard/Platform Multi-directional on rollerboard

17. Treatment outcomes Unsuccessful rehab –Episode of knee giving way –Status reduction from rehab candidate to high risk for reinjury on retesting Outcome measures –MVIC quadriceps –Single-limb hop tests –Knee joint laxity –KOS-ADLs –KOS-Sports –Global Rating Scale

18. Results Greater number of subjects in the standard group had unsuccessful rehabilitation (χ 2 =5.27, critical value=3.84, P<.05) Positive likelihood ratio was 4.88 ([11/18]/1–[7/8])

19. Results KOS-ADLS interaction. P<.05 KOS-Sports interaction. P=.12

20. Results GRS interaction. P<.05 X-over Hop interaction. P<.05

21. Hop Testing Perturbation (Immed after) Perturbation (F/u) Standard (Immed after) Standard (F/u) Single Hop101%(±14%)*68%(±48%) X-over Hop105%(±13%)104%(±16%)100%(±15%)64%(±55%) Triple Hop99%(±12%)*59%(±51%) * P<.05 at follow-up

22. Conclusions  More subjects in standard group (50%) had unsuccessful rehab compared to pert group (92%)  ~5x more likely to successfully return to high-level activities if receive perturbation training  Pre to post training ADLs, GRS, X-over hop improved in both groups  Post training to follow-up Maintained in pert group, in standard group

23. Development of Dynamic Stability Chmielewski et al, J Electromyo & Kinesiology 2002 9 subjects –Passed screen and wanted to attempt to return to activity Quadriceps strength testing Screening exam

24. EMG testing VL, LH, MG, SOL Muscle timing onset Termination of activity Muscle activity duration Time to peak amplitude Peak amplitude Integral of muscle activity during loading response

25. Training Perturbation training Agility training Resistance strength training for quads, hams, and gastrocs

26. Screening examination Pre trainingPost training Quadriceps index90.9%(±12.5%)91.3%(±5.8%) Timed Hop97.3%(±7.95%)96.0%(±4.9%) KOS-ADLs91.8%(±6.6%)97.3%(±2.3%)* GRS83.7%(±13.6%)94.3%(±4.3%)* P<.05

27. EMG testing * VL integral of activity during walking is significantly increased after perturbation training (p<0.05) VL activity integrated from 100 ms before initial contact to peak knee flexion is less before training (a) compared to after training (b).

28. EMG testing Timing of muscle activity during walking before and after perturbation training

29. Conclusions Quadriceps activity integral after training Relationship of quadriceps activity, peak magnitude, time-to-peak activity with hamstrings and soleus activation –Influenced by training Self-reports sports, functional test