JOINTS & Articulations

JOINTS & Articulations

Joints occur where 2 bones meet. They may:

• join two bones with as little flexibility as possible

• join two bones with a little ' give'

• join two bones with a maximum flexibility

JOINTS & Articulations

FIBROUS JOINT

• Ends of bones are separated by fibrous tissue vs. cartilage

• E.g. sutures of the skull (movement during birthing only), gomphosis (teeth in maxilla)

JOINTS & Articulations

CARTILAGINOUS JOINT

• cartilage sandwich with bone on either side

• bone and cartilage fit together perfectly and the whole thing is cup shaped

E.g. sternoclavicular joint

JOINTS & Articulations

SYNOVIAL JOINT

• Ends of bones move freely on each other;

• Sliding surfaces are covered with a thin layer of articular cartilage (coefficient of friction <0.002) E.g. knee joint

Classification of Joints

Complexity

• Simple - 2 articular surfaces (1 male + 1 female)

• Compound (elbow joint = humerus & ulna / humerus & radius / ulna & radius)

Classification of Joints

Degrees of Movement (freedom)• Uniaxial - joint which moves substantially

in one plane (like an elbow)• Biaxial - moves in two planes• Triaxial - moves in three planesA ball and socket is multiaxial, but is

equivalent to a triaxial as it has three degrees of freedom

Classification of Joints

Shape - probably the most widely used classification

• 1.hinge joints: permit flexion and extension (knee)

• 2.pivot joints: allow rotation (superior radio-ulnar)

• 3.gliding or plane joints: have flat surfaces and allow gliding in several directions (carpus and tarsus)

Classification of Joints

• condylar joints: usually regarded as two hinge joints with separate articulations (TMJ)

• saddle joints: have surfaces shaped like two saddles - allow movement in two planes at right angles and a little rotation (base of thumb)

• ball and socket: allows very free movement around any axis through ball (hip)

• ellipsoid: ball and sockets which are not round; rotation therefore impossible (radiocarpal joint)

Classification by function

• Movements at two bone ends are made up of:1. gliding of one surface over another - slide 2. angulation of one surface over another – roll

• 3. rotation about bone axis - spin

Synovial Joints:Related Structures

Ligaments • strong connective tissues that run from

bone to bone & help maintain stability in a joint;

• not elastic & can lose their ability to perform correctly when over stretched/torn

• collateral – attach on medial & lateral aspects of bones to provide support

Synovial Joints:Related Structures

Fibrocartilage• occupies the space between certain bones to

form the articular surface;• can take on many sizes & shapes;may be round/disk-like (IVD & TMJ) or flat/circular

(meniscus) or exist as a lip or edge to deepen a joint (GH labrum)

• resilient & functions as a shock absorber• avascular & relies on synovial fluid for

nourishment; can suffer injury (tears)

Synovial Joints:Related Structures

Synovial Membrane

• thin tissue surrounding most freely moving joints;

• membrane secretes synovial fluid which provides nourishment for cartilaginous disks, lubrication, and hydrostatic cushioning

Synovial Joints:Related Structures

Joint Capsule

• tough fibrous sheet that surrounds many joints & functions to protect them and provide stability

Synovial Joints:Related Structures

Bursae

• liquid-filled membranes that protect soft tissues as they pass by bony projections (eg. subacromial bursa of shoulder)

Synovial Joints:Related Structures

Fat pads

• literally, small pads of fat tissue to fill in gaps between bones & cushion bones

Synovial Joints

Synovial Joints-Tibiofemoral

Synovial Joints-Iliofemoral

Synovial Joints-Shoulder Complex

Synovial Joints:Injuries- Osteoarthritis

Synovial Joints:Injuries- GH Subluxation- Dislocation

Humeral Head

Glenoid fossa

Scapula

Clavicle

Synovial Joints:Injuries-OUCH

Synovial Joints:Injuries-HELP

Rotator Cuff and Anatomy Pathology