Joints

Joints

•         Union or junction between two or more bones or cartilages.

•         Varities in forms and functions.

•         More in child.

•         classification

Structural classification:

•         Fibrous joints

•         Synovial joints

•         Cartilaginous

                    

Functional classification

•         Synarthrosis; immovable articular surfaces are joined by fibrous tissue.e,g. sutures of the skull.

•         Diarthroses or synovial joints freely movable the articular surfaces are joined by fibrous capsule.

•         Amphiarthroses

•           slight movement . Presence of a pad of cartilage the edges of articular surface joined by fibrous tissues.e,g. intervertebral disc.

•         Fibrous joints

•         Sutures; connected by short strands of dense CT, special to the skull ,immovable,,bony margin may be plane,serrate,denticulate.

•         Syndesmosis;interosseous lig connects the articular surface.

•         Ghomphosis: peg  in socket w/short ligament e.g.tooth in its socket.

•        
Sutures; special to the skull ,immovable, bony margin may be plane, serrate, denticulate.

•         Joint cont.

Syndesmosis

•         interosseous lig connects the articular surfaces.

    e.g.middle tibiofibular joint and

•         Middle radioulnar joint

•         Ghomphosis:

•         tooth in its socket

•         Cartilaginous joints

•         Primary cartilaginous joints(Synchondrosis)

•         a plate of hyaline cartilage joins the articular surface which later replace by bone.e.g.joint between the epiphysis and diaphysis,costochondral

 joint.

•         Secondary cart. Joints(Symphysis)

•         a layer of hyaline cartilage united by the disc of fibrocartilage.

 e.g.symphysis pubis,manubriosternal joint.

•         Secondary cart. Joints;

•         Synovial joints

•         Most mobile of all. various degree of movement is possible.

•         Articular surfaces covered by hyaline cartilage.

•         Components of SYNOVIAL JOINTS

•         Articular capsule: Made of 2 layers

–       Fibrous: external, dense CT for strength

–       Synovial membrane: internal, produces synovial fluid

•         Synovial fluid: viscous; in capsule and articular cartilages

•         Reinforcing ligaments extracapsular/intracapsular

•         Nerves + vessels: Highly innervated, Highly vascular

•         Meniscus (some): fibrocartilage; improves the fit of 2 bones to increase stability

•         Synovial Joint

•         Bursae & Tendon Sheaths

•         Bursae: flat, fibrous sac w/synovial membrane lining

•         Tendon Sheaths: elongated bursae that wraps around tendons

•         3 Factors in Joint Stability:

–       Muscle Tone

–       Ligaments

–        Fit of Articular Surface

•         Synovial joints

•         Fibrous capsule lined by the synovial membrane.

•         Joint Shapes

•         Hinge: cylindrical end of 1 bone fits into trough shape of other

–       uniaxial

–       permit flexion and extension only.

–        (eg) elbow, ankle, interphalangeal

•         Hinge joints

•         The articular surfaces pulley shaped. e,g. elbow,  ankle and interphalangeal joints.

•         Plane

    -articular surface in flat plane

–       Short gliding,sliding movement

–       (eg) intercarpal, intertarsal, articular processes of vertebrae

·       Saddle: articular surface both concave + convex

–       side-to-side, back-forth movement

 carpometacarpal jt of thumb

.

  

•         Biaxial joints

•         Movement:flexion,extension,adduction and abduction.

•         Condyloid: egg-shape articular surface + oval concavity

–       side-to-side, back+forth movement

–       (eg) metacarpophalangeal (knuckle)

–       Condylar joint

•         Articular surfaces two condyles (convex male surface) and concave female surface)

•         Reciprocally fitted

•         Movement mostly in one plane only.,partly to next plane around a vertical axis.

•         Knee joint,temporomandibular joint.

•         Ball + Socket:

•         spherical head +  cup shaped socket

–       multiaxial movement

–       (eg) shoulder, femur

•         Ball and socket joint

•         Flexion,extension,adduction,abduction,medial rotation,lateral rotation and circumduction.

•         Pivot:

•         round end fits into ring of bone + ligament

–       rotation on long axis

–       (eg) prox. radius/ulna, atlas/dens

•         Pivot joint

•         A central bony pivot  surrounded by an osteoligamentous.

•         e.g. central atlanto-axial joints,

•         Pivot joint

•         Ellipsoid joints

•          articular surfaces  oval,convex,male surface fitting into elliptical concave female surface.

•         Flexion and extension in the transverse plane and abduction and adduction in the anterio-posterior plane.

•         e.g.wrist joint,metacarpophalangeal joint.

•         Common joint injuries

•         Sprains--stretch ligament, loose joint

•         Cartilage tears--fragments freeze joint

•         Dislocations (luxation)--bones out of normal alignment

•         Inflammatory and degenerative

•         Bursitis and tendonitis

–       Arthritis--over 100 types 

•         Osteoarthritis (OA)

–       Rheumatoid arthritis (RA)

–       Gout