Ligament (+ Tendon) Flashcards
Give 3 features of ligaments?
- Attach bone to bone
- stabilise joint
- restrict movement
Give 4 features of a tendon?
- Attach muscle to bone
- Transfer force from muscle to skeleton
- Facilitate movement
- Store and return elastic energy
What are ligaments/tendons made up of?
- cells –> Fibroblasts
- water
- collagen
- proteoglycans
- elastin
- uniform structure
What are the strengths of the tendon/ligament structure dependent upon?
The cross sectional area
- The more collagen fibres the greater resistance to stretch
What is the formula for tensile stress?
Force / CSA
What is the formula for strain?
Change in length / Initial length
What is the operating range of a ligament?
1.5-2.5% strain
What is the operating range of a tendon?
2.5-7% strain
Why is is difficult to measure force and strain in ligaments in vivo?
most of implantable transducers are estimators of stressors
Where are common ligament injuries?
Knee - ACL - Medial collateral ligament Ankle - ATFL - CFL
Describe the mechanisms of lateral ankle sprains
A combination of ankle inversion and internal rotation
- this places high strain on ATFL and CFL
What is the process of healing ligaments?
Influx of blood cells to damaged area = imflammation
New collagen fibrils laid down but not arranged as normal
Scar tissue forms which has different stiffness properties
Scar tissue slowly remodels –> more normal
what is the repair process of a ligament?
- requires the 2 ends of the ruptured structure to be apposed
- or surgical repair
What are the risk factors for lateral ankle sprains?
- Previous ankle sprains
- poor ankle stability
- poor ankle muscle length
- nature of the sport
Briefly describe Contact ACL tears in American football
Unhappy triad of O’Donoghue
- when lateral force is applied to the knee when the foot is planted
- ACL, MCL and Medial Menicus (lateral meniscus damage due to compression)
