Biomechanics and MS Phys Flashcards
What is Wolff’s Law
Tissues adapt to the forces applied to them
What must be considered for a patient to return to function?
How can we get them to use the leg immediately
Balancing enticing to use limb vs protecting underlying condition
What is important about fracture repair
Early weight bearing is necessary for return to function
What are the components of the joint?
Joint capsule
Synovial fluid
Articular cartilage
Subchondral bone
What are the sections and functions of the joint capsule?
Outer fibrous: mechanical support, originates from periosteum - Sensitive to pain or stretching to joint
Inner Synovial: composed of synoviocytes - needed for phagocytosis, hyaluoronic acid production
What is synovial fluid composed of?
Plasma ultrafiltrate and hyaluronic acid
Where does cartilage receive its nutrition
Synovial fluid - has no blood or lymph supply
What are the functions of synovial fluid?
- Supports articular cartilage
- removes metabolic waste
- Lubricates joint - inflammation leads to decreased viscosity - decreased lubrication
What factors are necessary for joint nutrition and waste removal?
Weight bearing and joint motion
What are the function of chondrocytes in articular cartilage
Produce proteoglycans (needed for compressive strength
What is the function of collagen in articular cartilage
Produces tensile strength
What is the function of articular cartilage
Absorb shock
- Has lots of water
Why is cartilage bad at healing
- Lots of water
- No blood or lymph supply
What is subchondral bone and what is its function?
- Absorb and distribute forces
- Decrease load on cartilage
What law of physics is important for returning to function
Force = mass x acceleration
What are factors that destroy cartilage?
High impact loading - abnormal forces on a normal joint
High contact pressures: normal forces on an abnormal joint
What are examples of an abnormal joint?
- Injury to joint or surrounding tissues
- Surgical alterations to joint (e.g TPLO)
What are examples of abnormal pressures to a normal joint?
Overuse and high impact secondary to sport
How can forces be decreased to a joint?
Decrease mass (weight loss vs UW treadmill)
Low impact training (derease acceleration)
- Minimize inflammation during initial acute inflammation
What are side-effects of immobilizing jionts
- Proliferation of adhesion
- Cartilage atrophy
- Decreased proteoglycan and collagen
- Decreased synovial fluid
How should mobilization, be reintroduced to limb after being imobilized?
Slow and gradual
- High intensity exercises damage limb
What effects do continued high impact have on joints?
Decreased PG synthesis
SC bone sclerosis
Damage to cartilage
What are the benefits to long-term low-impact cartilage
- Maintains joint health
- Low-impact activity does not degenerate joint in long-term
What is osteoarthritis
Irreversible articular cartilage degeneration, fibrillation, erosion
What are changes noted in an arthritic joint
- Joint capsule becomes thickened (decreased ROM)
- Synovial fluid becomes less viscous
- Cartilage becomes eroded
- Subchondral bone becomes thickened/ sclerotic
What does decreased range of motion typically lead to
Compensation in another joint
What is the function of a tendon?
Connects muscle to bone
- Bad at healing
What is the function of a ligament?
Connects bone to bone
- Bad at healing
What is the issue with chronic overuse of tendons or ligaments?
Microfractures that can lead to progressive disruption or failure over time
What part of the tendon is most susceptible to injury
Myotendinous junction
What is a tendinopathy?
Generic term including clinical and pathologic damage to tendon
What is tendinitis?
Active inflammation of the tendon
What is tendinosis?
Degenerative condition with lack of inflammation
- Painful
- Results in chronic pain pathway remodeling
What occurs with chronic over-use injury?
Neuromuscular remodeling attempting to cause a negative feedback mechanism
What is the return to function for tendons after injury in 6 weeks? 1 year?
50%
80%
What is a motor unit?
A single neuron and all the muscle fibers innervated by it
- All units should simultaneously fire when stimulated
- Fiber number equivalent to amount of control needed
What are type I muscles needed for
Postures - aerobic
What are type IIa used for
Aerobic/ anaerobic exercise
What type of muscle atrophy will be seen with denervation injury?
- Rapid loss of type II fibers primarily
- Seen very rapidly due to muscle size
What type of muscle atrophy will be seen with immobilization injury?
- Loss of type I fibers
What factors influence mechanical properties of tissues?
- Temperature (e.g. ultrasound)
- Load rate
- Frequency of loading
What functions are controlled by ventral nerve roots?
Motor
What functions are controlled by dorsal nerve roots?
Sensory
- Dorsal rami supply epaxial muscles
What are common injuries seen with peripheral nerves?
- Stretch: tail or brachial plexus avulsion
- Compression: crushing injury with secondary ischemia
- Neuropraxia: nerve conduction block without anatomic disruption
How fast does nerve grow?
1 mm/ day
