PEP 294: Lecture Notes
V. Joint
Joint Architecture (pp. 118-124)
1. Classification
 | Synarthroses: |
- immovable, fibrous joints
- suture: bone sheets mate closely & held by fibers -- skull
- syndesmosis: held by ligaments -- mid-radioulnar, mid-tibiofibular
| Amphiarthroses: |
- slightly movable, cartilaginous joint
- synchondrosis:
held by thin layer of hyaline cartilage -- sternocostal, epiphyseal plate
- symphysis:
thin plate of hyaline cartilage separates disc of fibrocartilage from bone -- vertebral, pubic symphysis
| Diarthroses (synovial joints): |
- freely movable
- articular cartilage, articular capsule, synovial fluid
- ligaments
- bursa, tendon sheath: reduce friction between tendon and bone
- meniscus: knee joint
- gliding joint (arthrodial):
(a) allows non-axial gliding only
(b) no DOF
(c) intermetatarsal, intercarpal, intertarsal, facet joints of vertebrae
- hinge joint (ginglymus):
(a) convex vs. concave
(b) 1 DOF
(c) humeroulnar (elbow), interphalangeal
- pivot joint (trochoid):
(a) allows rotation around one axis
(b) 1 DOF
(c) proximal & distal radioulnar joint, atlanto-axial joint (between the 1st and 2nd cervical vertebrae)
- ellipsoidal joint (condyloid):
(a) ovular convex vs reciprocally shaped concave
(b) 2 DOFs
(c) radiocarpal joint
- saddle joint (sellar):
(a) shape of riding saddle
(b) 2 DOFs
(c) carpometacarpal joint of thumb
- ball & socket joint (spheroidal):
(a) reciprocally convex & concave
(b) 3 DOFs
(c) hip and shoulder
2. Major Joints in Human Body
| Shoulder: glenohumeral joint (Figure 7-3) |
- glenoid fossa vs. humerus
- ball & socket joint
| Elbow: humeroulnar joint (Figure 7-20) |
- humerus vs. ulna
- hinge joint
| Wrist: radiocarpal joint (Figure 7-28) |
- radius vs. carpals
- condyloid joint
| Hip: acetabulofemoral joint (Figure 8-1) |
- acetabulum vs. femoral head
- ball & socket joint
| Knee: tibiofemoral joint (Figure 8-11) |
- femur vs. tibia
- hinge joint
| Ankle: talocrural joint (Figure 8-19) |
- tibia & fibula vs. talus
- hinge joint
| Spine: intervertebral joint (Figure 9-2) |
- intervertebral disc
- symphysis (amphiarthrosis)
| Forearm: proximal & distal radioulnar joints (Figure 7-21) |
- heads of radius & ulna
- pivot joint
| Neck: atlanto-occipital & atlanto-axial joints (Figure 9-1, 9-11) |
- atlanto-occipital: atlas (1st) vs. occipital bone (skull), condyloid joint
- atlanto-axial: atlas vs. axis (2nd), pivot joint
Functional Aspects of the Joint (p. 124-132)
1. Joint Stability
| Joint stability: |
- ability to resist dislocation
- prevents injuries to surrounding ligaments, muscles and tendons
- high stability desired
| Stability vs. shape of articulating bone surfaces: |
- general joint structure:
(a) reciprocally shaped
(b) tend to fit tightly together
- contact area vs. stability:
(a) wide contact area = high stability
ex: shoulder vs. hip
(b) different among joints and among individuals
(c) change in joint angle --> change in contact area --> change in stability
max. area of contact at the close-packed position
| Stability vs. arrangement of the connective tissues: |
- connective tissues (ligaments, muscles & tendons):
(a) affect the relative stability
(b) weak & lax connective tissues = low stability
- strengthening of the tissues --> increase in stability
- muscle activity & fatigue --> decrease in stability
- ex: Illiotibial tract of fascia lata:
(a) crosses lateral aspect of the knee
(b) contribute to knee stability
2. Joint Flexibility
| Joint flexibility: |
- ranges of motion (ROM) allowed at a joint
ROM: the angle through which a joint moves from anatomical position to the extreme limit of segment motion
- joint-specific
| Factors affecting flexibility: |
- shapes of articulating bone surfaces
- intervening muscle or fatty tissue
- laxity
- extensibility of the collagenous tissues and muscles
- fluid contents in cartilaginous disc
- temperature of collagenous tissues (warm-up)
| Flexibility vs. injury: |
- sources of injury:
(a) extremely low flexibility = high chance of tear or rupture
(b) extremely high flexibility = low stability
(c) imbalance between dominant and non-dominant sides
- injury prevention: high strength & flexibility desired
- stretching:
(a) regular stretching --> flexibility increases
(b) active vs. passive stretching
(c) ballistic vs. static stretching