Biomech
5/20/99

Cartilage
•	cells are good and are able to repair, but there are very few cells
•	compression of joint surfaces gets nutrients to the cartilage
•	proteoglycans attract water w/charge
•	w/o movement cartilage dies and leads to fusion of the joint
•	8 wks immobilization leads to irreversible damage
•	osteoarthritis—one of the most common problems of the world
•	under normal wear and tear cartilage lasts 130 years
•	fixation and abnormal (a lot at once or repetitive stress over time) makes the cartilage last less time
•	how does a joint swelling?  usually has negative pressure w/only 5mL of fluid
•	bacterial infection
•	tear of joint capsule
•	meniscus—medial of knee has a vascular supply
•	joint capsule—acts like a filter for cells, sympathetic systems controls the amount of fluid
•	cavitation—journal of manipulative and physiological therapeutics V18, Number3, March/April 1995, p60
•	doesn't think you can adjust a swollen joint
•	fluid goes right back out where it belongs

Motion
•	frictionless
•	synovial fluid is a lubrication
•	elastohydrodynamic system
•	hyaline cartilage is elastic—compress and loss water
•	water comes out b/w the two joint surfaces
•	why don't you fall—slide across the water surface
•	synovial joint have very little friction
•	non-Newtonian friction
•	the faster you move, the less friction
•	well designed system
•	works well when we move
•	boundary
•	lubricin—glycoprotein
•	for static joints to keep cartilage from rubbing on each other
•	like hairs on a hair brush
•	proteoglycans have the negative charge and holds water in the joint
•	keeps surfaces from touching
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