JOINTS

• all skeletal muscles attach to bone/connective tissue at at least 2 points

  • muscle’s origin connects to less moveable of two bones

  • muscle’s other end connects to movable bone/insertion

  • when the insertion is brought towards the origin —> movement happens

classifications of joints based on movement:

• synarthrotic — joints don’t move

• amphiarthrotic — joints partially move

• diarthrotic —> full movement

classfications of joints based on tissue:

• fibrous - dense connective tissue, these joints lie between bones that closely contact one another

  • a thin layer of dense CT joins the bones

  • examples are sutures, where there is little movement (synarthrotic)

  • some joints have limited movement like the joint beteen distal ends of the tibia and fibula

• cartilaginous - cartilage tissue

  • hyaline cartilage or fibrocartilage connects these bones

  • joints of this type separate the vertebrae, known as intervertebral disc

  • allow limited movement (amphiarthrotic) due to the slight flexibility of the tissue

• synovial - synovial fluid tissue, the most common kind

6 types of synovial joints:

• plane - sliding and twisting movements

  • articulating surfaces are flat/slightly curved

  • found in the wrist/ankle + in the articular processes of adjacent vertebrae

  • sacroiliac joints and the joints formed by ribs 2–7
    connecting with the sternum are also plane joints.

• hinge - flexion + extension movements

  • convex surface of bone bone fits into the concave surface of another

  • found in elbow and joints of phalanges

  • uniaxial

• condylar - movement in 2 planes only + no rotation

  • also known as ellipsoidal joint, the ovoid condyle of one bone fits into the elliptical cavity of another bone

  • example is the joint between metacarpals and phalanges

• pivot - rotation around central axis

  • also known as trochoid joint, the cylindrical surface of one bone rotates within a ring formed of bone/ligament

  • only rotation around central axis

  • helps you twist your body

  • joints between the atlas and the dens of the axis is of this type

• ball/socket - movement in all planes + rotation

  • also known as spheroidal joint, consists of a bone with a egg-shaped end that articulates with cup-shaped cavity of another bone

  • movement in all planes — multiaxial + rotational movement around a central axis

  • shoulder and hips are examples of these joints

• saddle - 2 planes + some variable movement

  • also known as sellar joint, this joint forms between bones whos articulating surfaces have both concave and convex regions

  • the surface of one bone fits the complementary surface of the other

  • joints between a carpal (trapezium) and metacarpal of the thumb

parts of a synovial joint:

• fibrous capsule —> outside fluid of joint

• synovial membrane —> membrane of fluid cushioning the joint

• synovial fluid —> fluid cushioning the joint

• joint cavity —> filled with synovial fluid

• articular cartilage —> structure found at epiphysis of bone

• joint (also known as articular) capsule —> made up of fibrous capsule and synovial membrane, mostly made up of dense connective tissue + filled with an inner lining at synovial membrane —> the synovial membrane secretes synovial fluid

• ligaments —> strengthen and hold joints together

parts of a patellar joint:

• menisci — C-shaped piece of tough, rubbery cartilage, acts as a shock absorber between femur and tibia, usually between articulating surfaces of the bone

• suprapatellar bursa —> bursa above your knee joint, provide cushioning and reduce friction

• prepatellar bursa —> bursa in front of your knee joint, reduces friction between patella and skin

• infrapatellar bursa —> bursa below your knee joint, reduce friction between patellar ligament and overlying skin

• bursae (general) —> fluid-filled sacs, line with synovial membranes, commonly located between tendons and underlying bony prominences,

  • aid movement of tendons that glide over bony parts

• articular cartilage —> structure found at epiphysis of bone

• synovial membrane —> membrane of fluid cushioning the joint

types of joint movement:

• abduction - move away from midline

• adduction - move towards midline

• flexion - decrease angle of joint

• extension - increase angle of joint

• dorsiflexion - specific to the foot, decrease angle and move foot up towards the shin

• plantar flexion - specific to the foot, increase angle and point foot/toes

• medial rotation - move arm inwards

• lateral rotation - move arm outwards

• circumduction - spins arm around, circular motion

• pronation - turn in

• supination - turn out

• inversion - sickling

• eversion - winged feet

• protraction - punching out

• retraction - punching in

• elevation - shoulders rise

• depression - shoulders sag