Michael A. Hunt PT, PhD Department of Physical Therapy University of British Columbia Vancouver, Canada

1. Year in Review: Mechanics
Michael A. Hunt PT, PhD
Department of Physical Therapy
University of British Columbia
Vancouver, Canada

2. Disclosure Information
Michael A. Hunt PT, PhD
Associate Professor
University of British Columbia, Vancouver BC Canada
I have no financial relationships with commercial interests to disclose
My presentation does not include discussion of off-label or investigational use

3. Sticking with tradition

4. Publication Overview
• Approximately 200 relevant papers from 461 unique search
hits
• Vast majority of papers were:
– in living humans (75%)
– focused on the knee joint (69%)
– motion capture-based (56%)

5. Breakdown by joint/area

6. Breakdown by equipment/technique

7. Popular areas/themes
• 1. Effects of rate of loading/force development
• 2. Relationships between joint loading and imaging-based
outcomes
• 3. Using mechanics to predict clinical outcomes

8. Effects of rate of load on cartilage damage
• Chondral explants from neonatal
calves
• Razor blade rig used to create
controlled cuts into the tissue
• Critical force needed to cut, depth of cut, and energy of cut were
calculated

9. Effects of rate of load on cartilage damage
• At faster blade speeds, first cut
occurred
– at lower critical force
– at lower blade depth
– with lower required energy

10. Rate of force development – effects on gait
• Longitudinal study of 24 patients
post-TKA
• Used multiple linear regression to
examine factors predictive of knee flexion excursion
- demographic
- clinical
- functional

11. Rate of force development – effects on gait
• Rate of quads torque development,
but not overall strength was predictive

12. Popular areas/themes
• 1. Effects of rate of loading/force development
• 2. Relationships between joint loading and imaging-based
outcomes
• 3. Using mechanics to predict clinical outcomes

13. Loading and compositional MRI - healthy

14. Loading and compositional MRI - healthy

15. Loading and compositional MRI - healthy
• Location-specific contact force impulse on
medial condyle:
– Positively correlated (r=0.78) to weight-bearing
cartilage thickness
– Inversely correlated (r=-0.71) to T1ρ relaxation time
• Regional variations in all measures based on load experienced
• Potential adaptations in healthy individuals to load may
include thicker cartilage and higher proteoglycan density

16. Loading and compositional MRI – chronic ACLR
• Longitudinal study up to 3 years post-ACLR
(n=31); Control group (n=16)
• Kinetic data during a drop-landing task
• T1ρ relaxation time

17. Loading and compositional MRI – chronic ACLR
• Reduced loading on ACLR knee; compensated by increased loading on Contralateral knee at 6
months
• No differences in T1ρ at Baseline; higher T1ρ in ACLR at 3 years

18. Loading and compositional MRI – chronic ACLR
• Larger interlimb asymmetry (more negative side-to-side
difference) was correlated with T1ρ increase over time

19. Popular areas/themes
• 1. Effects of rate of loading/force development
• 2. Relationships between joint loading and imaging-based
outcomes
• 3. Using mechanics to predict clinical outcomes

20. Progression of Hip OA
• n = 57 with mild or moderate hip OA
• Motion analysis and MRI grading
– Progression defined as (increase in cartilage, labrum,
BML, or cyst scores)

21. Progression of Hip OA
• 22/57 progressed at 18 months
1.1 times higher risk of progression for every 1° increase in flexion

22. Progression to TKA
• n = 157 with follow-up testing (~6 years
post-TKA)
• Focus on contralateral knee status

23. Progression to TKA
• n = 37 underwent contralateral TKA
At baseline, they exhibited:
- LESS knee flexion during loading
in BOTH knees
- LESS knee extension during
midstance in the initial TKA knee

24. Clinically-available measures
• Single-leg hop tests can be used to:
• Examine PROMs in patients with degenerative
meniscal tears
• Examine risk of post-traumatic OA after
ACL

25. Growing interest
• Mechanical impact of meniscal impairment on clinical and
structural outcomes

26. Growing interest
• Wearable technology to quantify and monitor mechanics
outside the laboratory setting

27. In need of help!
• Area still dominated by the knee joint

28. hand OA:
2 SRs, 2 RCTs
hip OA:
1 SR, 2 RCTs
knee OA:
6 SRs, 23 RCTs
PFP across the lifespanOA regions evaluated
general OA:
1 SR
36 papers included
Compliments of Dr. Natalie Collins

29. In need of help!
• Area still dominated by the knee joint

30. In need of help!
• More longitudinal data to identify mechanical markers relevant
to both clinical and structural progression
• Much larger datasets
– Likely requires multi-centre studies
– From cell to animal to human
– Joint-specific