Biomechanics of tendons and ligaments Flashcards
LIGAMENT FUNCTION
- Transmit tensile forces from bone to bone • Strong enough to provide stability
- Flexible enough to permit joint motion
Vertebral ligaments
Anterior & posterior longitudinal ligaments
• Superficial layer – fibres span several levels
• Deep layer – fibres cross only adjacent vertebrae, attach to annulus fibrosis
• Regional differences in size – thickest in thoracic region
• Ligamentum flavum
• Thick, elastic ligament connects lamina (vertebral canal wall) • Under constant tension (elastic) • Provides continuous compressive force • Prevents buckling during movement (helps you ‘spring back up’)
PULLS VERTEBRAE TOGETHER
EXTRA SPRING = COLLAGEN ELASTIN
Plantar ligaments
- ANKLES
- 3 integrated arches –2 longitudinal/ 1 transverse
- Determined by: • Bony arrangement
- Plantar ligaments
- Plantar aponeurosis
- Functions to adapt to surfaces & dampen impact forces
Anterior cruciate ligament
- Resists anterior tibial translation and rotational loads
- Complex anatomy - 2 bundles
- Non-linear load-elongation curve
- Ability to stabilise knee in various positions and loading conditions
- Common sporting injury (females 4 times more likely)
Tendon function
• Transmit force from muscle to bone (joint motion)
• Absorb, store and release energyàmaximise exercise efficiency
(conserve energy)…muscles are expensive to change length
• Power amplification (store slow and release fast – catapult)
• Protect muscle from damage (power attenuation – shock absorber)
Energy Storage Tendons
•Achilles and patellar tendons are the predominant energy storing tendons
•Energy storage tendons have increased elasticity and fatigue resistance (COMPLIANCE)
(most fail at 3.3%, Achilles > 12%)
•During single leg hopping, Achilles tendon contributes up to 16% of total body work by energy storage & release (Litchwark and Wilson, 2005)
Energy buffering tendons
During jump landing or walking down a hill, tendon lengthens before muscles to prevent eccentric damage
Energy amplifying tendons
During stance, Achilles tendon slowly stores and quickly releases energy during push-off to propel to the next step
Slow Storage + Rapid Recoil = more power!
Achilles tendon
- Fascicles of Achilles tendon spiral 90 deg. during descent • Allows elongation & elastic recoil for energy release
- MG fairly parallel
- LG and soleus insert onto calcaneus with strong torsion
- Important for intra-tendinous strain distribution
- Regional variations within Achilles tendon strains during walking (function?)
The ilio-tibial band stores energy
- The human IT band evolved for energy storage (chimpanzee vs human comparison) – stores up to 7J of energy during running (14% of Achilles)
- One of most common overuse running injuries
Mechanical properties of tendon affect muscle output
- A more compliant tendon requires a higher level of muscle contraction before force is generated around a joint.
- There is a delay between the activation of a muscle and its production of force – the electro-mechanical delay.
- more compliant tendon = greater electro-mechanical delay, less force transmitted for given change in length.
Aponeurosis
• •
An aponeurosis is a broad sheet of dense regular connective tissue Attaches muscle to bone or muscle to muscle or muscle to fascia
ENTHESIS VS MUSCLE-TENDON JUNCTION
Enthesis
• Tendon/ligament to bone insertion
• Aids load transfer between elastic tendon/ligament and rigid bone (100x stiffer than tendon/ligament)
• can be fibrous (inserts directly onto long bone) or fibrocartilaginous (4 distinct zones with a gradual transition) or muscular (attachment of muscle to bone without a tendon)
MUSCLE-TENDON JUNCTION
• Abrupt rather than gradual transition
• Collagen fibres and muscle cell membrane interdigitate to increase surface area and reduce stress between tendon and muscle
