Lecture 28 - Tendon and Ligament Flashcards
Ligament
Connect bone to bone
3 functions of a ligament
1) Hold skeleton together
2) Provide stability to joints
3) Limit freedom of movement
What are the 2 structural components of ligaments
1) Cells
2) ECM composed of Type I collagen and elastin
T or F: Type I collagen fibrils are densely packed in ligaments
T
What are 2 methods of attachment for ligaments
1) Direct: Fibers attach directly to bone
2) Indirect: Ligaments attach to superficial (blend into periosteum) or deep fibers (attach directly to bone)
Do ligaments have blood supply
Yes, but vascularization varies by ligament
What are the 2 types of nerves that innervate ligaments
1) Mechanoreceptors
2) Pain
Stress strain curve of a ligament
What are the 3 grades of ligament sprains
4 phases of ligament injury healing
What are 4 structural changes that occur to ligaments after healing
1) Altered proteoglycan and ratio of collagen fiber types
2) Failure of collagen cross-link maturation
3) Persistence of small collagen fibril size
4) Abnormal innervation
What 4 factors effect ligament healing
1) Grade of injury (size of gap)
2) If the injury was isolated (heals better)
3) Type of ligament as some heal better than others due to different vasculature
4) Whether contact was made between ligament ends (ACL vs MCL injury)
What are the 2 phases of healing with a patellar tendon graft following an ACL reconstruction and describe them
1) Intra-articular healing: Necrosis, vascularization, cell proliferation, collagen formation, and remodeling and maturation occur
2) Bone to tendon healing within the bone tunnel: Bone plugs to bone tunnel and tendon to bone tunnel form
Tendon
Connect muscle to bone
What are 2 functions of tendons
1) Force transmission between muscle and bone
2) Energy storage
What 3 cells make up the tendon and their function
1) Tenoblasts: Immature tenocytes
2) Tenocytes: Synthesize collagen and all components of ECM
3) Chondrocytes: At bone insertion
What are the 2 components of the ECM of tendons and what is found within these components
- Fibrillar Component: Type I and III collagen, elastin
- Interfibrillar Component: Proteoglycans, glycosaminoglycans
Glycosaminoglycans function
Allows for greater tensile loading
What is the hieararical order of tendons
1) Endotenon
2) Epitenon
3) Paratenon
4) Synovial tendon sheaths
Endotenon
Covers primary, secondary and tertiary fibre bundles
Epitenon
Loose connective tissue sheath that covers whole tendon and contains vascular, lymphatic and nerve supply to tendon
Paratenon
Loose connective tissue that consists of type I and III collagen, and elastin that acts as an inner lining for synovial tissue
Synovial Tendon Sheath
Found in areas of increased mechanical stress because it provides lubrication to reduce friction
What are 2 points of attachment for tendons
1) Bones: Can be direct (bone) or indirect (periosteal)
2) Muscle: Blending of collagen fibers and muscle cells
Where is the structurally weakest site mechanically for the muscle-tendon unit
Where the muscle attaches to tendon
What is the consequence of tendons having a low metabolic rate
They heal slower with injury
T or F: Tendons have vasculature in all 4 of its layers
T
Where would we find reduced blood flow in tendons
Around bony prominences
Where can we find tendons that have hypovascularity
1) Supraspinatus
2) Achlles tendon
What are 3 types of mechanoreceptors for tendons and their function
1) Pacinian corpuscles: pressure and vibration
2) Ruffini endings: stretch
3) GTO: pressure and tension (at insertion of tendons into muscles)
Tensile strength of tendons is related to
thickness and collagen content
T or F: Strenuous activities place high demand on tendon, with eccentric contractions generating the highest force on a tendon
T
Stress-strain curve for a tendon
What are 2 types of tendon injury and how they occur
1) Tendon rupture: laceration, degeneration
2) Tendinopathy: overuse
What are the 4 phases of healing for a tendon injury
For a quadriceps tendon tear describe how and where it occurs and its signs/symptoms
Treatment of a quadriceps tendon tear depends on what 3 factors
- Size of tear
2) Activity level
3) Age of individual
When would we do surgical treatment vs conservative treatment for quadriceps tenon tear
Surgical: Complete tear
Conservative: Partial tear
T or F: A quadriceps tendon tear results in a 50% decrease in weakness of the quad
T
T or F: After remodeling, biomechanical and mechanical properties always return back to normal
F, the tendon tissue nerve matches intact tendon tissue
What is a common site for a chronic tendon rupture
Supraspinatus
What are 3 irreversible changes of a tendon rupture on muscle tissue
1) Atrophy
2) fatty infiltration
3) Loss of muscle strength
Describe surgical repair effects on a tendon rupture
Tendon to bone healing does not result in normal tendon-bone insertion site and frequent re-separation occurs that can fill in with scar tissue causing loss of function
What are 3 terms that are used to describe overused tendons
- Tendinopathy: Tendon overuse
- Tendinosis: Describes the extracellular matrix imbalances in tendinopathy
- Tendinitis/Tendonitis: Inflammatory condition
What are 3 age-related changes that affect tendon and ligament tissue
- Loss of water content from matrix reduces ROM
2) Increased cross-linking increases stiffness and reduces ROM - Loss of elastic fibers cause less give to tendons and ligaments
What are 4 effects of immobilization of ligaments and tendons
1) Decreased collagen content
2) Decreased cross-linking of collagen making weaker biomechanically
3) Subperiosteal bone resorption at ligament insertion site
4) Decrease in tensile strength of ligament
What are 3 effects of exercise on tendons and ligaments
1) Increased collagen concentration and cross linking resulting in increase tensile strength and stiffness
2) Tendon hypertrophy from chronic increased loading
3) Structural and mechanical changes
