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
