1. Joints
Dr. Anderson
GCIT

2. Joints Where two or more bones meet Function Connection (ligaments)
Movement (muscles)
Protection (joint capsule)

3. Joint Classification Structural Functional
Fibrous – synostoses (immovable), syndesmoses (variable movement), gomphoses (peg-in-socket)
Synarthroses – bones don’t move relative to each other
Cartilaginous – synchondroses, symphyses
Amphiarthroses – “slightly” moveable
Synovial – articulating bones are separated by a fluid-filled cavity (most joints)
Diarthroses – freely moveable

4. Sutures
Fibrous joints, slightly mobile in youth, immobile as adult (e.g. cranial sutures)
Limited mobility allows brain to grow during development
Immovability as adult serves as a protective function
Top of Skull (newborn baby)

5. Syndesmoses Bones connected exclusively by ligaments
Movement varies according to length of the ligaments forming the joint, e.g.:
Very limited movement between tibia and fibula
Very pronounced movement of ulna around radius

6. Gomphoses Peg-in-socket, fibrous joint
Only example is the teeth in their alveolar cavities connected by the periodontal ligament

7. Cartilaginous Joints Articulating bones are united by cartilage
Synchondroses and symphyses

8. Synchondroses
Cartilage that unites two bones (such as the epiphyses to the diaphyses in the long bones of children and young adults)
E.g. Epiphyseal plates

9. Symphyses
Where articulating bones are lined with cartilage, which is fused to a pad or plate of fibrocartilage
E.g. – intervertebral discs, pubic symphysis

10. Synovial Joints Features
1. Articular cartilage – covers opposing bone surface
2. Synovial cavity – space that contains synovial fluid
3. Articular Capsule – provides tensile strength and covers all surfaces not lines with cartilage
4. Synovial fluid – provides joint lubrication, released from the cartilage itself during activity (weeping lubrication)
5. Reinforcing ligaments
6. Nerves and blood vessels -

11. Joint Structure

12. Articular Discs (Menisci)
Fibrocartilage pads that partially or completely divide the synovial cavity
(Knee, jaw meniscus)
Improve the fit of some articular surfaces in the joint

13. Bursae and Tendon Sheaths
Fibrous connective tissue that serves as a pliable “ball bearing” for some joints (e.g. shoulder) and closely packed tendons (e.g. wrist)
Bursa rolls in opposing direction of movement

14. What holds joints together?
Articular Surfaces -Deeply fitting articulations more stable than shallow ones
Ligaments – “cables” of dense regular connective tissue that hold the joint together
Relatively little stretch (can snap)
Muscle Tone – low levels of contractile activity – more tone = more stable joints

15. Synovial Joint Structure

16. Joint Movements Originates from muscle contraction (of course)
Degree of joint movement is called “range of motion”
Three main types
Gliding
Angular
Rotation

17. Gliding joints Simplest movement
One or more flat (usually) bone surfaces glide over another
Wrist bones
Ankle bones
Between vertebrae

18. Angular Movement Flexion – pulling the joint angle closed
Extension – opening the joint angle
Hyperextension – greater than normal extension
Abduction – moving a limb away from the median line of the body
Adduction – moving a limb toward the median line of the body
Circumduction – moving a limb in a cone-shaped path in space

19. Rotation Turning of a bone around its long axis
Medial rotation – turning toward the midline
Lateral rotation – turning away from the midline

20. Supination and Pronation
Refer to movement of radius around the ulna
With arms down at sides:
Supination is a lateral rotation of the palms (palms anterior or up)
Pronation is a medial rotation of the palms (palms face posteriorly, radius and ulna cross each other, forming an ‘X’)

21. Ankle and Foot Movement
Dorsi flexion – moves foot up (superiorly)
Plantar flexion – moves foot down (inferiorly)
Inversion – sole of foot turns medially
Eversion – sole turns laterally

22. Jaw movements
Protraction and retraction – jutting jaw out and bringing it back, respectively
Elevation and Depression – Moving a body part superiorly or inferiorly (e.g. jaw)

23. Synovial Joint Types
Plane (Gliding) – allow only short, gliding movements (wrist and ankle)
Hinge (One angular direction) - allows motion only along a single plane (flexion and extension only)
Pivot (Rotation) – allows the bone to rotate around its axis
Condyloid (All angular directions)– Oval articulating surfaces that permit movement in all directions
Saddle (All angular directions)– both articular surfaces have a convex AND a concave side that articulate together
Ball-and-Socket - (Universal movement) allows movement in all directions, including limited rotation

24. Knee Joint Very Complex 4 bones
Femur, tibia, fibula, patella
Ligaments often injured in sports or accidents

25. Torn ACL (Arthroscopic view)
Knee Injuries
Cruciate Ligaments
ACL (anterior)
PCL (posterior)
Deep in joint cavity of knee (intracapsular)
Can tear and separate femur from the tibia
Most often happens when the knee is rotated during full extension
Torn ACL (Arthroscopic view)

26. Knee Injuries
Most dangerous injuries are lateral blows to the fully extended knee
Torn menicsi
Torn collateral ligaments
Tibial (Medial or MCL)– outside hit
Fibular (Lateral or LCL)– inside hit

27. Jaw Joint Problems
Jaw Joint (mandible and mandibular fossa) is called the tempero-mandibular joint (TMJ)
Loosely connected – has a greater range of motion than other hinge joints
Condyle of mandible can move out of the fossa, (anterior disarticulation)