1B Joints and Cartilage

skeletal system components

bones

cartilage

ligaments

skeletal system functions

support the framework of the body

protection - shields vital organs from injury

force translation - bones work with muscles and joints to produce movement

blood cell production - bone marrow is found inside certain bones and produces blood cells

mineral storage

types of cartilage

elastic cartilage

hyaline cartilage

fibrocartilage

elastic cartilage

specialized tissue with many elastic fibers

both flexible and strong to maintain structure shape, able to bend and return back to its original shape

where is elastic cartilage found

epiglottis - small flap in your throat that returns to shape everytime you swallow

auricle (external ear) - visble part of your ear that makes it flexible

laryngeal cartilages - cartilage in your larynx (voice box) that move during speech and swallowing

hyaline cartilage

most abundant found in the body

weakest cartilage type

smooth surface for gliding, flexibility, support, friction reduction

viscoselastic connective tissue (behaves both as an solid and fluid depending on the force applied)

spreads body weight across more of the surface to stablize stress on certain joints

where is hyaline cartilage found

Articular cartilage - covers the ends of bones inside synovial joints to allow bones to slide smoothly over each other and reduces friction

Trachea/bronchi - windpipe made of c-shaped rings of cartilage to keep airways open

Epiphyseal plate - found near the ends of long bones in children/teens to allow bones to grow longer, hardens into bone once growth stops in adulthood

fibrocartilage

durable for joint support and cushioning

shock-absorber

high amount of collagen

found in symphysis joints, often need to withstand large forces

where is fibrocartilage found

intervertebral discs - soft, pad-like discs between the bones of your spine, prevents vertebrae from grinding together during movement

pubic symphysis - connects the left and right sides of the pelvis from the front, allows for a small amount of movement but mainly for stability

menisci (knee meniscus) - two crescent shape pads in each knee to protect the knee joint from wear and injury

Chondrocyte

found in all types of cartilage

mature cartilage cell that produces and maintains the cartilage matrix (collegen + elastic fibers)

Why is hyaline cartilage also called articular cartilage?

it covers the articular surfaces of bones (where they touch when forming a joint) in synovial joints

different of synovial and synchondrosis joints where hyaline cartilage is located

synovial:

• bones are not directly connected

• has a joint cavity (gap between the non-connecting bones)

• joints used for moving freely

synchondrosis:

• bones are directly connected

• no joint cavity

• little to no movement

• joints used for growth or stability

avascular

all types of cartilage has no blood vessels, lymph vessels, and nerves

cartilage doesn’t get nutrients or oxygen from blood

Femoral condyles

rounded ends of the thigh bone at the knee

coated with a smooth layer of hyaline cartilage

What happens to hyaline (articular) cartilage when a joint is loaded (force/weight is applied) and then unloaded (release of force/weight)?

When the joint is loaded, pressure pushes fluid out of the cartilage into the synovial cavity.

When the pressure is released, fresh synovial fluid containing nutrients flows back into the cartilage.

Nutrient and waste exchange happens via synovial fluid:

• superfical zone spreads the load sideways

• middle zone holds the fluid that gets unloaded and loaded

• deep zone anchors cartilage to bone so it doesn’t slide off from pressure

interstitial fluid

60-80% of water contains lipids and electrolytes

found in all types of cartilage in all tissues

types of arthritis

Osteoarthritis (OA) and Rheumatoid arthritis (RA)

what does a healthy joint look like (before arthritis)

Osteoarthritis (OA)

most common type of arthritis

gradual loss of cartilage from “wear and tear”

common causes of hip and knee replacements

Rheumatoid arthritis (RA)

autoimmune disease

inflammation of synovial cavity and cartilage decreases your mobility over time

eventually cartilage degrades and leads to exposed bone ends

nutrient change issues

classifying synovial joints by how many directions they can move

More movement = less stability
Less movement = more stability

uniaxial (moves one direction), biaxial (moves in two directions), multiaxial (moves in many directions)

uniaxial

hinge - back and forth

pivot - rotation around one axis

very stable, limited movement

Biaxial

Planar (gliding) - sliding

saddle - back-forth, side-side

condyloid (ellipsoid) - two directions + cirsumduction

moderate stability, moderate range of movement

multiaxial

ball-and-socket - rotation, bending, straightening, abduction (moving away from the midline), adduction (moving toward the midline)

most movement, least stable

Factors contributing to range of motion

shape and arrangement of articulating surfaces - tight fit = less movement, loose fit = more movement

ligaments crossing the joint - ligaments are strong bands that limit how far a joint can move, more/tighter ligaments = less movements

surronding muscles - muscles around a joint hold it in place when they contract during movement

its a balancing act to maximize function when limiting chances of injury by increasing stability, you cannot have both extremes at the same time

ligament sprains

torn ligaments are called sprains

Grade 1:

• Stretching or slight tearing

Grade 2:

• Incomplete tear

Grade 3:

• Complete tear

• needs immediate surgery

PRICE procedure for sprains

what to do when you get a grade 1 or 2 sprain:

Protection

Rest

Ice

Compression

Elevation