Joint Struture And Function

Question 1

Synarthrosis, Amphiarthrosis, & Diarthrosis

Answer 1

Synarthrosis- little to no movement

Amphiarthrosis- allows restrained motion

Diarthrosis- designed for movement
Ex: synovial joints are diarthrotic

Question 2

Name the 7 elements a synovial joint always has

Answer 2

1. Joint cavity filled with synovial fluid
2. Articular cartilage covering the ends of bones
3. Joint is enclosed by a joint capsule
4. Inner layer is synovial membrane
5. Outer layer is fibrous layer- reinforced by ligaments
6. Capsule is supplied by blood vessels
7. Capsule is supplied by sensory nerves for pain and proprioception

Question 3

Glycosaminoglycans and water’s effect within the ground substance of a connective tissue in a joint

Answer 3

GAGs bond with and hold water which causes tissue to swell

Tissue will swell to the point where its pressurized, increases its ability to resist forces

If tissues aren’t properly hydrated and pressurized, they dont function well

Question 4

Tendons and retinaculae

Answer 4

Tendons consist of collagen fibers arranged parallelly to pull strongly in one direction

Retinaculae are pulleys that restrain/strap tendons in place, near or across joints

Function: to prevent bow stringing! They maintain a near constant moment arm length throughout range of motion

Question 5

Structural differences between tendons and ligaments

Answer 5

Tendons: collagen fibers arranged parallel to one another

Ligaments: arranged in different directions to resist force in several dominant directions

Question 6

Structure of a joint capsule

Answer 6

No parallel or regular alignment of collagen- crisscrossed weave pattern

No uniform tension throughout range of motion of the joint because it allows for free movement

Fibers lengthen in the direction of the load

Question 7

Articular cartilage

Answer 7

Most resilient, adaptive connective tissue

Forms load bearing surfaces of bones

Functions to reduce pressure at the joint surface and to reduce friction between joint surfaces during rotation

Question 8

Immobilization

Answer 8

Immobilization is the enemy!

Depriving a joint of stress (movement) alters the bio mechanical properties of all the connective tissue in a synovial joint

Decline in mechanical properties happens much faster than the time it would take to regain mobility

Can cause contracture: temporary or permanent loss of mobility

Question 9

Contact pressure vs contact force vs contact area

Answer 9

To decrease contact pressure, you have to decrease contact force or increase contact area

Ways to decrease contact force:
force = mass x acceleration
- Decreased body weight decreases the force
- Decreased muscle force requirements- activity modification, adaptive equipment, manipulation of external moment arm
- Increase shock absorption via special shoes/orthotics in the lower limbs

Ways to increase contact area:
- Reduce joint malalignment with a splint, brace, orthotics
- Know your limitations
- Might need surgical correction
- Activity movement modification (“avoid ____ and _____ which may further misalign your joints”)