Pathology and rehabilitation of tendons and ligaments Flashcards
Structure - Composition - Function
- Tendon & ligament can change their structure and/or composition (and thus their function) in response to changes physiology (maturation, ageing), injury or other disease processes
- If one structure at joint is affected, the total function of the joint will be disrupted
- Rehabilitation should consider behaviour of all the affected structures/ induce adaptation in each structure.
Tendon and ligament injury is common!
- Tendinopathy accounts for 30-50% of all sports injuries, plus 48% of of occupational injuries
- Achilles tendinopathy accounts for 7-11% of running injuries
- Knee ligament injuries estimated 2 per 1000 people per year in general population
- Rotator cuff tears occur in >30% people over 60 years of age
Mechanics of ligament injury
- Ligaments fail when tensile loads exceeds capacity
- Often awkward position of landing
- Joint dislocation is often associated with ligament damage
- Abnormal motion between bony articulation predisposes to articular damage
Mechanics of ligament injury - grading
Grade 1: damage to some collagen fibres
• Grade 2: more extensive number of fibres damaged - increase laxity
• Grade 3: complete rupture - more substantial increase in laxity but bony end feel
Ligament Healing
- Continuous process
- 3 overlapping phases
- Inflammation
- Proliferation - start laying down new tissue to fix
- Remodelling - collagen needs to be aligned in direction of stress
Normal ligament
- little Hypocellular
- little Hypovascular
- Highly organised
- Dense collagen structure
ACL repair
10 days - defect filled with vascular inflammatory tissue
• 3 wks - inflammatory cells subsided and active fibroblasts dominated
• 6wks - decrease in number and size of fibroblasts + some evidence of longitudinal alignment of nuclei (along long axis of ligament)
• 14wks - remodelling – increased re- alignment and decreased cell numbers
• 14-40wks - few changes noted; cells remained larger and more numerous
Healing of ligament - mechanical properties
• Decreased stiffness (lower slopes)
• Decreased load at failure (all times)
• Altered site of failure (entire ligament is weakened)
Healed ligaments are generally more bulky and not as strong as native tissue
Healing of ligament - morphology
- Increased cross-sectional area (all times)
* Progressive decrease in CSA from 3-14wks • Laxity increased at 3, 6, and 40wks
When to operate on lig ?
Intra-articular ligaments (inside joint) • lower healing capacity • E.g. ACL, PCL, scapholunate ligament (wrist) • Often require surgery
meanwhile
Extra-articular ligaments (outside capsule) • High healing capacity • E.g. ankle, collateral ligaments of knee or elbow • Often treated conservatively
lig injuries can be associated with
- Instability
- Bony bruising
- Osteoarthritis - didn’t heal properly over time
Tendon function
• Transmit tensile forces
• Mechanical properties of tendon affect muscle function (force
generating capacity + muscle length-tension relationship) • Storage & release of energy for efficiency
• Buffering, amplifying role
Mechanics of tendon injury
Injury can be produced by mechanical overload due to:
1. Excessive force
2. Repeated overload
3. Normal forces applied to weakened tendon
• Degenerative changes may weaken the tendon’s mechanical properties predisposing to injury
• 97% of ruptured Achilles tendons had asymptomatic degenerative change
Mechanics of tendon injury 2
- Stress-shielding
• Even if whole tendon is exposed to normal mechanical loading, some fibres may be underloaded (stress-shielded) and other fibres over-loaded - Forces applied in alternative direction
• Tendon compression frequently contributes to insertional tendinopathy eg: Achilles or Gluteus medius tendons
tendons rupture at >8% stress
tendon injury
• Also consider effects of:
- Ageing
- Adiposity – mechanical loads + systemic effects
- Physical activity levels – spikes in acute load relative to chronic loads
- Diseases e.g. diabetes, rheumatoid arthritis
- Medications e.g. corticosteroids - suppresses fibroblastic reaction and inhibits growth
- Alcohol – inhibits fibroblast proliferation
Overuse tendinopathy
- May occur at different sites: • Mid-substance e.g. Achilles
- Insertional e.g. Achilles, lateral elbow (tennis elbow), patellar tendinopathy
- Musculotendinous junction e.g. hamstrings, quadriceps tendon
Paratendinitis
- Occurs where a tendon rubs over a bony protuberance
- De Quervains (APL, EPL)
- FHL (near medial maleolus)
- Acute oedema, hyperaemia of paratenon
- Inflammatory cells
- Tendon itself minimally involved
- Crepitis (fibrinous exudate fills shealth)
Tendon rupture
- Can occur in normal tendon if loads are sufficiently large
- Common tendons
- rotator cuff (older adults)
- Achilles (young, active adults)
- More commonly occurs in tendon weakened by pre-existing degenerative change (diabetes, excessive alcohol)
Overuse Tendinopathy
• Grey and amorphous to naked eye • Disorganised collagen (separation, fragmentation, disorientation) • Inflammatory & immune cells absent • increase cellularity • Hypervascularity • increase proteoglycans and water content (reason for darkness in images from ultrasounds)
Ultrasound imaging of tendinopathy
- Demonstrates tendon thickening, hypoechoic areas, tears (B-mode)
- Neovessels (Doppler) BUT …
- High sensitivity and low specificity for diagnosis of tendinopathy > negative ultrasound useful to rule out tendinopathy
- Limited correlation with pain severity
AT vs Patellar - opposite changes in elastic properties:
- Achilles tendinopathy- lower SWV (distal), greater thickness mid-tendon.
- Patellar tendinopathy -higher SWV at both regions, greater thickness proximally.
- lower Achilles tendon elastic modulus and higher patellar tendon elastic modulus.
Rehabilitation of tendinopathy
Exercise is a critical component • Reduce pain, increase loading capacity • Isometric exercise possibly superior ? • Improve function • Progressive loading to remodel tendon
• Avoid compressive loading, especially if insertional • (eg: prox hamstrings)
- Considerations…
- What is the loading history ?
- Gradual progression of loads • Address stability/coordination • No quick fixes (slow turnover)
Effects of immobilisation on ten. and lig
- A few weeks of immobilisation can decrease structural properties of tendons/ligaments
- Immature, weaker, disorganized collagen
- ê tissue stiffness up to 50% after 8 weeks of immobilisation • Tissue deterioration is less if immobilised in some tension
Effects of remobilisation & recovery
- Re-establishment of normal stresses can reverse effects, but …
- Tendons/ligaments are relatively hypovascular + hypocellular
- Healing is slow - takes many months and may never attain past characteristics
- Insertion sites are more resistant to recovery
Exercise training as rehabilitation
Key = Progressive loading to improve tendon “capacity”
- tendon and ligs remodel in response to applied stress
strength > energy storage ( concentric activity while lengthen > energy storage and release
