Joints are where bones meet, and can be solid (fibrous or cartilaginous) or fluid-filled (synovial). Synovial joints contain articular cartilage on the bone ends, a joint capsule, synovial membrane that lines the capsule and produces synovial fluid, and may contain discs or labrums. There are many types of synovial joints classified by their axis of movement (uniaxial, biaxial, polyaxial), freedom of movement (1 axis, 2 axes, 3 axes), and shape (hinge, pivot, ball and socket). Nerves innervate the joint according to Hilton's and Last's laws.
2. Definition of Joints
Interposed Substance: i) solid ii) Fluid
i) solid - Synarthrosis: a) Fibrous b) cartilagenous
ii)Fluid - Diarthrosis or synovial
Flat bones/ Irregular bones / Long bones
3. a) Fibrous Joints
1.Types : Sutures, gomphosis, Syndesmosis
Sutures - they are limited to flat skull bones.
Sutural ligament - unossified part of the mesenchymal sheet
Components : cambial layer, capsular layer, loose areolar tissue
Fate
Purpose
Gomphosis: Sockets & Pegs
Fate
Purpose
Syndesmosis; one interosseus membrane or ligament binds the two
Example: Inferior tibiofibular, Intercarpal, Intertarsal,
interchondral
Fate
Purpose
4. b. Cartilagenous joints:
•Primary or synchondrosis ii) secondary or symphysis
Primary - Between metaphysic and epiphysis with a hyaline
epiphysial cartilage, where a cartilagenous bone has more
than one ossification centre. Also in the base of skull,
sternebrae, vertebrae, hip bone, sacrum.
Fate
Purpose
Secondary- median, do not ossify, hyaline & Fibrocartilage
Fate
Purpose - deformity allows movement, binding - withstand
considerable torsional, shearing and tensile forces.
5. C/ Synovial joints
•Articular cartilage- hyaline, no nerve or vessel,
wear resistant, provide friction-free surface,
withstand great compressive, torsional, & shearing
forces
Nutrition- 3 sources
Thickness
X-ray appearance
•Joint capsule-
Fibrous + synovial
Attachment line of the cuff
Pierced by blood vessels, lymphatics and nerves
Rents
Relatively avascular, but rich nerve supply
6. •Synovial membrane –
intima of flat cells + subintima of cells and fibers
Highly vascular, pink, shiny, smooth
Bleeds heavily, but not painful to incision
Type A cells- Phagocytic
Type B cells – Secretory ( hyaluran, lubricatory glycoprotein)
Forms fat pads, folds, fringes to occupy potential spaces as
fillers
Characters of Synovial fluid –
•Intra-articular discs / meniscus –
where congruity is less
Joint cavity partitioned,
Increase congruity, Shock absorber, lubricating brush,
facilitate combined joint movements, protection n of joint
surface
•Labrum- fibrocartilagenous annular lip attached to the joint
margin to increase area of contact and to deepen the socket
7. Classification of synovial joints:
Simple/ compound / complex
Uniaxial / Biaxial / Polyaxial
With 10 freedom of movement / With 20
freedom of movement / With 30 freedom of
movement
Plane / Hinge or ginglymus/
Pivot or trochoid / Bicondylar/ Ellipsoid /
Sellar / Spheroid or ball and socket
8. Movements of a synovial joint –
Gliding / angulation / rotation
Flexion- Approximation of ventral
surfaces around a transverse axis
(except at ankle)
Adduction- / Abduction movement
around an anteroposterior axis
(except at shoulder/ thumb/ digits)
Rotation – ConJunct + adJunct
