Joints Flashcards
Joints
- Bones articulate at joint
- Allow movement and stability
Functional Classification of Joints
Synarthrosis – Immobile
Amphiarthrosis – Slightly Mobile
Diarthrosis – Freely Mobile
Structural Classification of Joints
Fibrous – Dense CT
Cartilaginous – Hyaline or Fibrocartilage
Synovial – Ligaments (contains synovial cavity and fluid)
Synostosis – Bone
Fibrous Joint: Suture
- Bones linked by thin layer of fibrous CT
- Interlocking edges
- Located in skull
- Immovable
Fibrous Joint: Syndesmosis
- May be slightly moveable
- Forms interosseous membrane or ligament
o Bones held together by collagenous fibres - More CT linking bones than in sutures
Cartilaginous Joint Types: Synchondrosis
Hyaline cartilage links bone
o Can facilitate longitudinal growth of immature long bones (epiphyseal plate)
Cartilaginous Joint Types: Symphysis
Bones joined by pad of fibrocartilage
o Compressible, strong, flexible
o Limited movement possible
Synovial Joint
- Most type of joint
- Typically, diarthroses
Classifying Synovial Joints
Axes of Movement
- Nonaxial, Uniaxial, Biaxial, Multiaxial
Shape
- Plane/Gliding, Hinge, Pivot, Condyloid, Saddle, Ball and Socket
Gliding (Plane) Synovial Joints
- Articular surfaces are essentially flat
- Allow short gliding movements (nonaxial)
- Some can be classified as amphiarthroses
Hinge Synovial Joint
- Cylindrical projection (convex) fits into trough-shaped surface (concave) of another bone
- Motion is along a single plane (uniaxial – permitting extension and flexion)
Pivot/Trochoidal Synovial Joint
- Allows rotation along the axis of the bone (uniaxial)
- Rounded end of one bone protrudes into a sleeve composed of bone or ligaments
Condyloid Synovial Joint
- Permits movement in 2 planes (biaxial)
- Oval-shaped (convex) articular surface fits into complimentary depression (concave) of another bone
Saddle/Sellar Joint
- Permits significant movement in different planes (multiaxial)
- Each articular surface has both concave and convex areas
- E.g., carpometacarpal joint
Ball and Socket Joint
- Freely moveable joint (multiaxial)
- Spherical head of one bone articulates with a cup-shaped socket of another bone
Synovial Joint: The Shoulder Joint
- Glenohumeral or Humeroscapular Joint (Ball and Socket articulation)
- Head of humerus articulates with glenoid cavity
o Relatively shallow and loose joint
o Freely moveable joint
Supported by:
o Ligaments
o Tendons of muscles
o Rotator cuff muscles
Shoulder Joint: Articulating Surfaces
- 1/3 of head of humerus fits into glenoid cavity
- Very moveable by liable to dislocation
Shoulder Joint: Ligaments and Tendons
- Improve stability of shoulder joint
- Tendon of the long head of the Biceps brachii stabilises joint
o Secured by the transverse humeral ligament
Synovial Joint: The Hip Joint
- Coxal Joint
- Ball and Socket articulation (multiaxial)
- Head of femur articulates with acetabulum of coxal bone
o Acetabulum forms deep socket for head of femur
o More stable than shoulder joint (less moveable)
Joint supported by:
- Ligaments
- Tendons of thigh and hip muscles
Synovial Joint: The Knee Joint
- Articulation between femur, tibia, patella
o One of the largest/most complex synovial joints in the body - Primarily a hinge joint
o Joint capsule encloses posterior/medial aspects
o Extensions of quadriceps tendon cover anterior aspect
Knee Joint Ligaments
Complex array of ligaments inside/outside the articular capsule
o Intracapsular ligaments are relatively uncommon
Intracapsular cruciate ligaments cross each other to form an X
o Prevent forward or backward displacement of tibia
Extracapsular collateral ligaments limit rotation of the extended knee
Knee Joint: Menisci
Contains two crescent shaped pads of fibrocartilage (lateral and medial menisci)
o Absorb shock – prevent femur rocking from side to side on the tibia
Joint Movements
At anatomical position, joints are in their zero position
Flexion
Reduces angle between articulating elements
