1. Articular System (Joints) ANHB 2212 – 2007 Avinash Bharadwaj

2. Joints  “Articulation”  Articulatio / Arthron  Arthrology  Where two or more bones or parts of bones unite…  How they are joined together… the tissues that unite bones

3. Joint Classification  Structural  The tissues that unite bones  Functional  Mobility or otherwise  Synovial joints – axes of movements  No perfect system (Explained as we go!)  Arbitrary and confusing terms  Overlapping terminology  Latin terminology and anglicised versions  The choice is yours!

4. Tissues Uniting Bones  Fibrous tissue  Unossified tissue between membrane bones (Explained fully next week!)  Ligaments (Dense connective tissue!)  Cartilage  Hyaline cartilage  White fibrocartilage  Fibrous capsule with a cavity  Special features for lubrication, movement and stability

5. Movable Joints  “Movability” (mobility…?) is a relative term!  Movement is always associated with restrictions  Active movements – by muscles  Movements due to other factors  Shapes of bony surfaces  Tensions in ligaments  Other external factors (pelvic joints in childbirth)  Passive movements in clinical examination

6. Fibrous Joints  Sutures (“stitches”)  Between flat bones of the skull Bone Periosteum Section (Magnified!) Surface view

7. Fibrous Joints  Syndesmoses  Inferior tibiofibular joint (Not shown here)  Interosseous membranes  Separation of compartments  Additional areas for muscle attachments  Some other ligaments…  Gomphoses  Tooth and bone  “Peg-and-socket” R U

8. Cartilaginous Joints  Synchondrosis – Hyaline cartilage  Growth mechanism  synostosis  Between primary and secondary centres  Between named bones (e.g. sphenoid + occipital) (Week 12 Histology!)  Symphysis – White fibrocartilage  WFC is deformable  Partially movable joints  Occasional cavities – ? Evolution of synovial joints Primary and secondary cartilaginous joints : terms best avoided. Functionally two distinct entities.

9. Cartilaginous Joints

10. Synovial Joints  “Freely movable”…?  Freedom is relative!  More movable than any other type…!  Fibrous tissue bond, with a cavity

11. Synovial Joints – Basic Features  The bones – articular surfaces  Smooth… but not quite!  Articular cartilage  Fibrous capsule  Ligaments  Capsular thickening  External  Synovial membrane

12. Synovial Joints – Articular Cartilage  Hyaline (WFC in membrane bones)  No perichondrium  Variable thickness  Depends on the type of joint  In curved surfaces  Convex – thick in the centre  Concave – thin in the centre

13. Synovial Joints – Capsule Etc  Capsular attachment  Thickening of capsule : “Intrinsic” ligaments  Areas of strength / weakness  Capsule may be loose in places  Other ligaments (“extracapsular”)  Synovial membrane and fluid

14. Intra-articular discs  White Fibrocartilage  Reduce incongruity  Modify movements  Spread of synovial fluid – reduce “drag”  Incomplete discs / menisci

15. Other Intra-articular Structures  Ligaments  Cruciate ligaments – knee joint  Tendons  Long head of biceps – shoulder joint  Popliteus – knee joint  Fat pads  Such structures are covered by synovial membrane.

16. Synovial Joints – Subtypes  Functional  Degrees of freedom  Uniaxial, biaxial, multiaxial  Structural  Shapes of bony surfaces

17. Synovial Joints – Subtypes  Plane : Sliding movements (“Non-axial joint”)  Hinge : Uniaxial (e.g. elbow)  Ball-and-socket : Multiaxial (Shoulder, hip)  Saddle : Two planes of movement + combinations  Bicondylar : Two pairs of surfaces  Pivot : Osseofibrous ring + rotating bone Nothing is perfect – do not expect geometrical shapes!

18. Two Types Illustrated Pivot joint – Osseofibrous ring and head of radius. Bicondylar joint – Knee Two pairs of articular surfaces

19. Bursae  Muscles / tendons in close proximity – friction  Bursa (Latin for purse!)  Thin walled connective tissue bag  Lining of synovial membrane  Between joint capsule and tendon / muscle, bone and tendon / muscle, or between muscles / tendons.  Bursitis – painful  Some bursae communicate with joint cavity

20. Joint Stability  Movement and stability – a compromise  Factors in stability  Bony configuration  Capsule and ligaments  Tendons and muscles  Sometimes blend with capsule – rotator cuff

21. Nerves  Rich sensory innervation  Capsule, ligaments, periosteum  Same nerves as those that supply muscles  Joint pain  Bony injuries  Capsular / ligamentous injuries  Synovial membrane  And more…

22. Blood Vessels  Rich blood supply  All parts except cartilages  Articular cartilage  By diffusion through synovial fluid  Blood vessels of surrounding areas (capsule, bone) Last Slide