Biomech
5-57-99

Three Things Bone needs to heal
Blood supply
Immobilize
Proximation

Weakness of cartilage
No blood
No nerve
No lymph

Strength lost w/broken bone—all that are immobilize
2% bone strength (1.8%)
0.9% mass

Elasticity—B—more strain
Strongest—A—more stress

Purpose of tendon—attach muscle to bone
•	composite figure—looks like muscle at one end and bone at the other
•	twice at strong as the muscle
•	the tendon is much stronger
•	tendon is designed not to tear
•	muscle is most likely to tear
•	most common thing to see  is tear
•	w/tendon—irritation from repetitive movements—tendentious 
•	Achilles tendon tear most common due to stress we put on it esp w/high heels shortens the tendon, then put on tennis shoes and play tennis easily tears
•	grade 1, 2, 3
•	fibers run parallel

Ligament
•	limits and guides the ROM
•	bone to bone
•	most common—capsular, on every sinovial joint
•	disc—most common in spine
•	has very little elasticity 2-3% stretch rate
•	ligamentum flavum—80-90% elastic (lots of elastin)
•	fibers crisscross in all directions
•	no muscle attachment
•	bone protects and overlying muscles
•	acute injuries – b/c don't due repetitive movements out of normal range of motion
•	sprains
•	grade 1—no change in function, short duration, okay in a day or so
•	grade 2—plasticity—lengthened, hurts longer, swells, heals longer length, change ROM
•	grade 3—loss of ligament; surgery required
•	worst case is grade 2