ligament pathology

ligament composition

• cellular 20%, extracellualr 80

• primary cell - fibroblasts which control ligament metabolism > production and degradation

• produce all types of fibrous

• collagen mainly type 1 fibres (60%) but III, IV, V also present

• mechanotransduction

Mechanotransduction

more load results in bigger and stronger ligaments

lig comp

• less force resistant than collagen but more flexible

• elastin fibres smaller portion fibrous ECM componment than collagen

• elastin scarce in extremity ligaments

• proteoglycans group molecules with protein core and side chain sugars (GAGs); GAGs attract water and influences viscoelastic properties

ligament neurosensory capacity

4 types

• ruffini endings

• free nerve endings

• golgi

• pacinian corpuscles

tissue biomechanics

• greater CSA leads to increased stiffness and strength in ligaments.

• longer fibres increased elongation to failure, strength same, decreased stifness

viscoelastic properties

elasticity: the ability of a material to deform under stress and return to its original shape upon removal of the load.

viscosity: resistance to flow , fluid property and depends on PG/GAG and water composition

creep: fixed force applied and maintained, deformation (force constant but length changes)

stress-relaxtion: stretched to fixed length

strain-rate sensitivity: behave different in response to loading rate (fast vs slow)

do sprains precede rupture

animal models show

• no long term symptoms of pain or disability

• decreased ACL strength and knee joint remodelling

• altered movement control

grade 1 ligament strain

disruption of some collagen fibres

• localised tenderness on palptation

• minimal inflammation

• normal range and end feel on ligament stress test, but test may be painful

• little function deficit

grade 2

disruption of a considerable proportion of collagen fibres

• significant tnederness on palpation

• can be considerable infllamtion involving whole joint

• increased joint play on stress test, increased laxity but there is a definite end point present

• moderate functional deficit

grade 3

complete disruption of collagen fibres

• audible pop at time of injury

• painful immediately but then may become pain-free a short time after

• considerable swelling

• no end feel on stress test

• significant functional deficit

phases of ligament healong

1. bleeding and inflammation (1-7 days)

2. matrix and cellular proliferation (1-6 weeks)

3. remodelling and maturation (6 weeks to 12 months)