Tendons and Ligaments Flashcards
What are ligaments?
Ligaments
•Resist distraction of two bony attachments
•Collateral ligaments
•Suspensory ligament
What are tendons?
Tendons
•Passively transfer force generated by muscle to bones to provide movement
•Cross over joints
What are tendons and ligaments made up of?
Fibrils -collagen
Fibres
Fascicles
What is the anatomical structure of a tendon?
•Endotenon -Confluent with epitenon -Around fascicles -Contains vessels and nerves •Epitenon •Paratenon/tendon sheath
What is crimp?
•Crimp
•Wavy appearance of collagen fibrils under light microscope
•Responsible for part of the elasticity
•With loading core fibrils straightened first
Site of pathological lesions
What is crimp effected by?
Crimping also reduced with age and long-term exercise
Exercise accelerates age related degenerative changes
why do tendons take so long to heal?
have a very low blood supply (less than bone)
What is the blood supply of tendons?
•Blood supply -Musculotendinous junction -Osseous insertion -Intratendinous along endotenon •Diffusion -Tendon sheath -Synovial fluid
What is blood supply effected by?
- Blood flow highest in foals
- Decreases to adult levels by 3yo
- Increased by exercise
- Increased by injury
What are the cellular components of tendons and ligaments?
- Ligaments possess much higher cell population than tendons
- Tenocytes (tendon cells)
- Formation and maintenance of ECM
- React rapidly to mechanical stimuli
What is extracellular matrix made up of?
- Determine biomechanical characteristics
- 65% water
- 30% collagen
- 5% non-collagenous glycoproteins
What is collagen?
- 80% dry weight
- 95% type I collagen
- Covalent cross-links determine strength
What are non-collagenous glycoproteins?
- Cartilage oligomeric matrix protein [COMP]
- Assists in organisation of collagen network
- Proteoglycans
- Structural integrity
- Metabolism regulation
What is; Tendinitis Tenosynovitis Adhesive tenosynovitis Desmitis?
tendinitis- inflamed tendons
tenosynovitis- inflammatory condition occurring within a sheath
Adhesive tenosynovitis- tendons within a sheath stick together
desmitis- ligaments inflammation
What is an extrinsic tendon and ligament injury?
percutaneous injury or displacement
What is an intrinsic tendon and ligament injury?
strain or sprain
most common type of injury in horses
What is the range of tendon and ligament injuries?
- Individual fibril or fibre slippage- microdamage
- Individual fibril or fibre rupture- fibres out of alignment
- Progressive rupture of fibres/fascicles
- Complete rupture/tear
What are developmental issues in tendons?
•Load during growth affects COMP levels
(cartilage oligomeric matrix protein)
COMP associated with tendon strength
Lack of exercise during growth period reduces tendon quality
Too much exercise during growth increases risk of damage
•Crimp development affected by exercise during development
•After skeletal maturity tendon has limited ability to adapt
•Period of optimal conditioning of tendon for athletic performance
What is tendon mechanical degeneration?
•Mechanical degeneration •Low-grade mechanical forces Cumulative fatigue microdamage •Supra-maximal loading Clinical tendonitis
What is hysteresis?
- Loss of energy between loading and unloading cycles
- Heat
- Exercise-induced hyperthermia
- Hysteresis loop
- Up to 45ºC
- Reduction in normal synthetic cell activity
- Denaturing of ECM proteins
What is the tendon injury, vascular compromise?
•Vascular compromise
•Blood flow limited/abolished under maximal loading
•Some areas poorly perfused
Predisposed sites
•Tenocytes relatively resistant to hypoxia (lack of oxygen supply)
•Enzymes
•Imbalance between matrix synthesis and degradation
What is the tendon injury, tendinopathy?
- Tendinopathy
- Subclinical tendon degeneration
- Clinical tendinopathy
- Acute inflammatory phase
- Subacute reparative phase
- Chronic remodeling phase
What does the acute inflammatory phase of tendon repair involve?
- 1-2 weeks
- Intratendinous haemorrhage
- Oedema
- Infiltration of WBC
- Release of proteolytic enzymes (enzymes which break down bonds between animo acids)
- May cause expansion of lesion
What does the subacute reparative phase of tendon repair involve?
- Starts a few days after injury
- Peaks at 4 weeks
- Angiogenesis
- Accumulation of fibroblasts
- Resident tenocytes
- Endo/paratenon cells
- Circulating monocytes
- Synthesis of disorganised collagen (type III)
What does the chronic remodelling phase of tendon repair involve?
- Begins 6 weeks post-injury
- Progresses for 6-24 months or more
- Remodelling of disorganised scar tissue
- Cross-linking of fibrils
- Controlled loading promotes conversion and organised alignment of collagen fibrils
How effective is the healing of the tendon sheath?
•Poor healing •Lack of paratenon Lack of external blood supply •Adhesion formation allows angiogenesis (development of new blood vessels) and cell infiltration •Reduction of function of tendon
How do tendons repair?
Healed tendon lacks mechanical properties of original tissue • Often stronger • Poor elasticity Increased strain in adjacent tendon
Re-injury common
• Same tendon
• Contralateral tendon
• Other supporting structures
What are the functional characteristics of tendons?
Weight-bearing tendons
•Flexor tendons
•More elastic
•Energy stores
Positional tendons
•Extensor tendons
•Stiffer
What are the functional characteristics of flexor tendons and suspensory ligaments?
- Support fetlock joints during normal weight-bearing
- Large loads due to hyperextension of fetlock
- Considerable elasticity
- Store energy for energy efficient locomotion
What are superficial and deep digital flexor tendons?
•Highly pennate muscle
•Maximises power with minimal contraction distance
•Action: shock absorption
Fast gaits: functions like pogo stick
Reaches and maintains high speed with minimal energy expenditure
