MSK Week 7 - Ligaments Flashcards
Anatomy of ligament
- Epiligament layer
- Hypocellular: fibroblasts
- Hypovascular
- Mechanoreceptors
- Thickened bands in joint capsule of discrete cords
What are ligaments made up of?
Tightly packed bundles of collagen fibers, that are running in parallel, longitudinal to the ligament
What is the epiligament layer?
Mainly fibroblasts, vascular supply and mechanoreceptors
Intraarticular ligaments
Within the joint capsules (ACL/PCL of the knee)
Extra articular ligaments
Outside the joint capsule (LCL)
How are ligaments similar to tendon?
- Collagen fibers in longitudinal bundles with small cross links
- 70% water
- 70 - 80% dry weight is type I collagen
- About 5% elastin
Ligament properties
- Resist tensile forces
- Limit joint excursion
- Restrain abnormal motions
- On slack exhibit crimp
- Viscoelastic properties
What are the structural properties of ligaments?
- Connect bones
What is the motion property of ligaments?
Guide joints
How do ligaments play a proprioceptive role even though they’re “inert”?
- Mechanoreceptors
- Estrogen receptor
Mechanoreceptors
- Reflex arc - synergy with muscle
- Active and passive stability
- Functional joint stability - mechanical and sensory characteristics
Sprain (injury to ligaments) mechanism of injury
- High force tension - trauma
- Excess of tensile strain
- > about 4% collagen disrupted and sub-failure of ligament
- > about 8% strain —> total failure
What are contact high force tension?
External force
What are non-contact high force tension?
Deceleration or rapid direction change
Risk factors of sprains
- Attenuation of forces - recurrent microtrauma
- Genetic predisposition
- Inhibition/alteration of reflex arc in associated muscles
- Hormones
- Age
- Disuse —> decrease tensile strength
Ligament phases of healing
- Hemorrhagic
- Inflammatory
- Proliferation
- Remodeling
Hemorrhagic phase of healing
Hematoma in the gap, inflammatory recruitment
Inflammatory phase of healing for ligament
Clearance of necrotic tissue, neovascularization, granulation tissue, recruitment of cells
Proliferation of ligament phases of healing
- By 1st week, fibroblasts arrive last, begin collagen and other protein production
- By 2nd week, original clot more organized, capillary buds, collagen content high but disorganized
- Highest concentration of collagen present
Remodeling ligament phases of healing
- Gradual decrease cells, matrix becomes dense and organized
- Normalize water content and type I:III ratio
- Up to 3 years, never 100%
- 5th week - some tensile strength
- 6 months - 50% strength
- 1 yr - 80% strength
Intraarticular ligament healing
- Encased in synovium
- Less likely to heal without surgery
- Does not follow typical triphasic healing and timeframes
- Blood dissipates into synovium
- Hematoma prevented
- Limited arrival of growth factors and cytokines needed to mediate inflammation and healing
Extraarticular ligament healing
- Epiligament layer: highly vascular, highly cellular, sensory and proprioceptive nerves
- Greater likelihood of healing without surgery
- Follows typical triphasic healing and timeframes
Clinical signs of ligament injury
- History of trauma
- Point tenderness
- Joint effusion in more severe cases
- Joint ecchymosis in more severe cases
- Positive stress tests - joint gapping
- Imaging - MRI (especially for grading)
- Graded - 1, 2, 3
What are the decisions of management of ligament injury based on?
- Function of the injured ligament
- Degree of injury
- Timeframe
Protective phase management of ligament injury
- Control of swelling and pain - PRICEMEN
- Relative rest vs. complete immobilization
- Submaximal isometrics
- Pain free ROM (PROM, AAROM, AROM)
Controlled motion phase management of ligament injury
- Restore ROM
- Address kinetic chain
- Progression of strengthening
- Stabilization and proprioception (static, supported)
Remodeling management of ligament injury
- More advanced stabilization and proprioception (dynamic, complex, unsupported)
- Restoration of agility, power, speed for return to sport/occupation
Medical interventions for ligament injury
- Surgical repair: rehab is protocol driven
- Biological approaches
Growth factors biological approaches
Favorably alter healing environment
Gene therapy biological approach
Introduction of genetically modified cells to enhance healing
