Joint Structure and Function Flashcards
What is mechanotherapy?
The clinical application of mechanotransduction - where therapeutic exercise is prescribed to promote repair and remodeling of injured tissue
What does Wolfe’s Law explain?
Structure follows function
What are some types of connective tissue involved with joint structures?
Bones, bursae, capsules, cartilage, discs, fat pads, menisci, ligaments, and tendons
What is the extracellular matrix?
Part outside of the cell
Why are cells and the extracellular matrix important?
Determine the function of a joint - when the cells are squeezed, they are stimulated to produce more collagen
What are two types of deformation and what do they cause?
Tensile load (pulling) - causes elongation Compression load (pushing) - causes compression
What is stress?
Force per unit area - affected by how big something is
What is strain?
Elongation per unit length in response to tensile load
What are the three types of forces?
Tension, compression, and shear force
What is the correlation between length and thickness with regards to force?
If fibers that are the same length, the object with more fibers (thickness) will need more force in order for them to be the same length
What is the correlation between elongation and length with regards to strain?
An object with a longer length will have a longer elongation when compared to an object with a shorter length but the same amount as strain
What is the total failure percentage in a stress-strain curve?
8%
What does Young’s Modulus of elasticity explain?
A tendon that is damaged can be stretched the same length with a lot less force
What is viscoelasticity?
The combination of elasticity and vicosity
What is viscosity?
Resistance to flow
What is the importance of the speed of movement of flow?
When you want to stretch something, if you do it slower, then you will be able to do it longer
What is creep?
Force applied is the same over time and the deformation increases - object will slowly start to sink down
What is the stress-relaxation relationship?
Is tissue is stretched to a fixed length over time, the force required to keep that length would decrease
What is hysteresis?
The loading and unloading does not follow the same path due to energy lost as heat (ex: rubber band wearing out from constant push and pull)
What is the strain-rate sensitivity correlation?
When load is applied rapidly, the tissue is stiffer - stretch slowly
What does a tendon attach?
Muscle to bone
What does a ligament attach?
Bone to bone
What determines the tendon/ligament properties and what do they provide?
Elastin - provides elasticity
Collagen - provides strength
What is entheses?
Tendon and ligament attachment to the bone - indirectly via fibrous attachment and directly via fibrocartilage
Which is more elastic, ligaments or tendons?
Tendons
What is the relationship between tendons and ligaments and force?
Tendons and ligaments become stiffer with increased rate of force application
What are the two ways the tendon load can be increased?
Increase the external load (gravity) or increase the speed of movement
How does hopping affect the tendon load?
Increases the tendon load by 5x the body weight
How does temperature affect tendons and ligaments?
Increased temperature will decrease the stiffness, increase creep and relaxation, and decrease tissue failure limit
How does aging affect tendons and ligaments?
Tensile strength increases during childhood and you have maximal tensile strength at skeletal maturity (gradually declines during adulthood)
What is the SAID principle?
Specific adaptation to imposed demand
What is the effect of immobilization?
Decreases tensile strength and stiffness and causes contractures - can be minimized if tendon/ligament is elongated
What is the effect of exercise on tendons and ligaments?
Increases circulation and can minimize loss of strength associated with aging or injury
What is the function of a bursae?
Shock absorption and protection from compression
What is the hardest form of connective tissue?
Bone
What are the main functions of bones?
Serve as framework for body, serve as levers for muscle action, and protect viscera
Is bone static or dynamic tissue?
Dynamic
What are the three types of bone structures?
Cancellous bone - soft, inner layer
Cortical bone - hard, outer layer
Growth plates
What is the percentage of turnover in cancellous bone and cortical bone per year?
Cancellous - 25%
Cortical - 3%
-Higher turnover with cancellous bone because it is more fragile and has a different vascular station
Why is the compression on a bone more than body weight?
Compression is both body weight and muscle force
What are the two bending forces on bone when standing?
Compression - medially
Tension - laterally
What is anisotropy?
Bone has different mechanical properties in different directions
What is the relationship between density and activity with regards to bone?
Increased activity –> increased density
Decreased activity –> decreased density
What is the function of cartilage?
Distribute joint loads over as large an area as possible and allow contact and movement between two bony surfaces with minimal friction and wear
What is cartilage mostly composed of?
Water
What is the importance of glycosaminoglycans (GAG) in cartilage function?
Contains molecules that imbibe water which swells the tissue and gives it stiffness (helps disperse repetitive forces) and allows for nutrient delivery
What are three types of cartilage?
Hyaline - low friction
Fibrocartilage - high friction - found in joints
Elastic cartilage
Is joint cartilage avascular or vascular?
Avascular
How is cartilaginous compressibility affected by the rate of loading?
Rapid loading causes the cartilage to become stiffer
What happens to the fluid content of cartilage when subjected to a constant load?
Undergoes creep
How are compression of cartilage and shear forces related in creating cartilage failure?
Compression causes shear forces at cartilage-bone interface (shear stressed occur when liquid goes out the sides)
What are some mechanical factors that can cause osteoarthritis?
Obesity, repetitive loading, joint instability, and rapid loading
What is the relationship between exercise and cartilage?
High loading sports can cause increased osteoarthritis, ROM exercises cause increased fluid flow in and out of cartilage and moderate exercise causes an increase in gag count which increases tensile strength
What are two categories of joints?
- Diarthroses - synovial joints that allow free movement
2. Synarthroses - nonsynovial joints
What are two types of synarthroses joints?
- Fibrous joints - sutures, gomphoses, and syndesmoses
2. Cartilaginous joints - symphyses and synchondrosis
What are the two layers of the joint capsule?
Stratum fibrosum - outside, poor vascularization, rich innervation
Stratum synovium - inside, rich vascularization, poor innervation
What is the function of the stratum fibrosum and stratum synovium?
Stratum fibrosum - position and movement sense
Stratum synovium - produces synovial fluid
What are the three classifications of diarthrodial joints?
- Uniaxial - hinge and pivot joints
- Biaxial - condyloid and saddle joints
- Triaxial - plane and ball and socket joints
What is hypermobility and hypomobility?
Hypermobility - ROM exceeds normal
Hypomobility - ROM less than normal
What is osteokinetmatics?
Refers to the rotary movements of the ones in space during physiological joint motion
What is arthrokinetmatics?
Accessory motion - motion of the joint surfaces in relation to another
What are the three terms used in arthrokinematics?
Roll, glide, and spin
What is the convex on cave rule?
Roll and glide occur in opposite directions
What is the concave on convex rule?
Roll and glide occur in same direction
What is a closed-pack position?
Joint surfaces have maximal congruency and the ligaments and capsule are taut
What are the two parts of the extracellular matrix?
Fibrillar component - collagen and elastin
Interfibrillar component - water
