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Bones, cartilage, joints, dislocations and fractures
Costo = rib
Chondro = cartilage
Bone functions include support and protection of the body and vital organs, calcium
metabolism, RBC formation and attachment
Cartilage is less rigid and is located where mobility of the skeleton is required i.e. at joints
All joins are compromising – i.e. there is compromise between stability and mobility
↑ Stability = ↓ mobility and vice versa
All joint compromise profiles are different
Fibrous joints:
Syndesmoses: ~ mobility; ↑ stability; links bones with fibrous (e.g. interosseous) membranes
e.g. proximal and distal tibiofibular syndesmosis with IOM
Sutures: ↓ mobility; ↑ stability; sites of bone fusion
e.g. the coronal and sagittal sutures of the skull bones
Fontanelles: wide sutures of the neonatal skull, separated by fibrous membrane, divided
into anterior, posterior and lateral; permit the sliding of bones over each (=moulding) other
during birth, and therefore facilitating the passage of the neonatal skull through the birth canal
(especially between the coccyx and pubic symphysis).
Remain open until ~18 months with visible pulsation (absence of
pulsation/sinking membrane upon dehydration due to reduced CSF)
Cartilaginous joints:
Primary: synchondroses
Joined by hyaline (articular) cartilage
Only present in growing long bones; ossified and fused after full growth
Permit growth in length
e.g. epiphyseal growth plate
Secondary: symphyses
Fibrocartilage
Strong, ~ mobility
e.g. intervertebral disc – contains outer annulus fibrosus (criss-crossing fibrous laminae
of type I and II collage that ↑ stability) and inner nucleus pulposus (90 % water in neonates,
decreases with age  stiffness) which allows shock absorption. Each disc allows small
movement in all directions, with the summation of these movements allowing for considerable
movement of spine
Both synchondroses and symphyses can slip: slipped femoral epiphysis and discs
SYNCHONDROSIS PATHOLOGY: X RAY:
normal epiphyseal growth plate slightly
visible as a line dividing the epiphysis
(head) and the metaphysis (neck) of the
femur. Slippage of the epiphysis is
characterized by increased EGP visibility
and altered interrelation of epiphysis and
metaphysis
SYMPHYSIS PATHOLOGY:
Disc herniation (e.g. into spinal cord) is painful and can damage the
spinal cord, causing sensory or motor loss in areas innervated by the
damaged fibres.
Synovial joints: associated with 8 features:
1. Articulation of 2+ bones
2. Articular surfaces covered by hyaline cartilage
3. Surrounded by a capsule
a. Superficial fibrous layer (strong)
b. Deep synovial membrane ( synovial fluid)
4. Contain a joint cavity (filled with SF absorbing shock, nourishing and lubricating joint)
5. Supported by fibrous ligaments which ↑ stability and strength
6. Associated with skeletal muscle/fibrous tendons
a. Tendons insert ONTO bones lying at EITHER SIDE of the joint i.e. tendon has to
cross a joint in order to move it e.g. bicep contraction  elbow joint flexion
7. Associated with bursae which prevent joint friction
a. Either extensions of joint cavity or separate closed sacs (e.g. anterior to patella)
8. Other special features e.g. articular disc in TMJ joint
5 synovial joint subtypes:
1. Plane – minimal movement of flat surfaces in one plane
a. e.g. acromioclavicular joint
2. UNIAXIAL flexion + extension or rotation
a. Pivot – e.g. atlanto-axial joint
b. Hinge - e.g. elbow joint
3. BIAXIAL - ~ mobility in 1 plane>other planes
a. Saddle – e.g. carpometacarpal joint
b. Condyloid – (flexion/extension + abduction/adduction + circumduction) e.g.
metacarpophalangeal joint
4. Ball & socket – MULTIAXIAL mobility by fitting of rounded head into a concavity
a. e.g. hip joint and shoulder joint (the former has a deeper socket and is therefore
a tighter fit, more stable/less mobile and less prone to dislocation than the
latter).
Mobility: synovial>cartilaginous>fibrous
Stability: fibrous>cartilaginous>synovial
Hypermobility can be natural or pathological
Range of movement (flexion/extension + abduction/adduction + internal/external rotation) of
shoulder joint > hip joint
Pathology:
Ligament injurty/slipped disc with retention of articular surfaces in their
normal anatomical interrelationship
Subluxation: partial dislocation with reduced area of contact between
articular surfaces
Dislocation: complete loss of contact between articular surfaces
Commonly: craniovertebral, TMJ, shoulder, elbow,
acromioclavicular, hip, PIP/DIP, knee, pubic symphysis and ankle joints
Temporomandibular joint (TMJ):
Bilateral synovial articulation between mandibular fossa and the articular tubercle (eminence)
of the temporal bone superiorly and the head of the condylar process of the mandible inferiorly
Contains an articular disc
Dislocation: head of condylar process of mandible displaces and becomes stuck anterior to the
articular tubercle of the temporal bone
Unilateral  chin displaced to contralateral side
Bilateral  chin remains central
Nerve and arterial supply to joints:
High sensory nerve supply (pain, touch, temp, proprioception)
Arterial supply – articular branches - from large arteries e.g. popliteal artery.
Periarticular anastomoses common
Dislocation can damage articular branches, causing loss of distal pulses which indicates
compromised blood flow to areas distal to the joint (e.g. damage to popliteal branches can
prevent perfusion to the foot  necrosis  amputation).