Lecture 6: Synovial Joints

List structures present

Hyaline Cartilage, Joint Capsule, Joint cavity (potential space), Synovial membrane, Ligaments

Function of Hyaline Cartilage in Synovial Joints

Sits on flat ends of bones creating smooth, frictionless movement

Why is smooth, frictionless important in joints?

Reduces damage, reduces energy converted to heat

Joint Capsule

Sheet of DFCT wrapped around joint.

Function of Joint Capsule

Holds the bones together, prevents leakage of synovial fluid.

Joint Cavity

Potential space where needed for bones to move

Synovial Membrane

thin layer of cells that secrete synovial fluid

Function of Synovial Fluid

Fills in inside of joint cavity, contains nutrients for joint loading, reduces friction.

Ligaments

Bands of DFCT inside/outside the joint

Function of Ligaments

Holds bones together, restricts unwanted movement

Types of Ligaments

extracapsular (separate to joint capsule, outside joint), capsular (thickenings of joint capsule), intracapsular (separate to joint capsule, inside joint)

Hinge (example -2)

Ankle, elbow

Pivot (example - 2)

Neck/C1-C2 vertebrae, radioulnar

Condylar (example)

Knee

Ellipsoid (example)

wrist joint (radiocarpal joint)

Saddle (example)

thumb

plane (example - 2)

intercarpal/intertarsal joints

ball & socket (example - 2)

Hip/shoulder

hinge (axis)

uniaxial

pivot (axis)

uniaxial

condylar (axis)

biaxial

ellipsoid (axis)

biaxial

saddle (axis)

biaxial +

plane (axis)

multiaxial

ball & socket (axis)

multiaxial

hinge (movement)

flexion, extension

pivot (movement)

only rotation

condylar (movement)

flexion, extension, rotation (when flexed)

ellipsoid (movement)

flexion, extension, abduction, adduction, circumduction

saddle (movement)

flexion, extension, abduction, adduction, opposition (specialised form of rotation)

plane (movement)

sliding and gliding — flat surfaces

ball & socket movement

ALL - flexion, extension, adduction, abduction, rotation

plane

hinge

pivot

condylar

saddle

ball & socket

Capsular Ligaments

thickenings of the joint capsule in some joints where more support is needed — restrict movement away from themselves

Extracapsular Ligaments example in the knee (2)

MCL (medial collateral ligament)
LCL (lateral collateral ligament)

Intracapsular Ligaments

separate from joint capsule; additional bands of DFCT inside joint

Intracapsular Ligaments in the knee (2)

ACL (anterior cruciate ligament) and PCL (posterior cruciate ligament)

Fibrocartilaginous pads fucntion

fill in space, absorb shock and deepen articulation

Fibrocartilaginous pads in the knee

menisci are half shaped moon structures that sit between tibia and femur

Function of ACL

stops femur sliding backwards/post. displacement (post. femur → ant. tibia)

Function of PCL

stops femur sliding forwards/ant.displacement (ant. femur → post. tibia)

Function of LCL

restrict adduction

function of MCL

restrict abduction