1. Chapter 9
Articulations
(Joints) 9
Articulations

2. An Introduction to Articulations
Arthrology – science of joint structure, function, and dysfunction
Kinesiology – the study of musculoskeletal movement
Articulations/joints
Body movement occurs at joints (articulations) where two bones connect
A joint cannot be both mobile and strong. The greater the mobility, the weaker the joint. Joint strength decreases as mobility increases
Mobile joints are supported by muscles and ligaments, not bone-to-bone connections
Joint name – typically derived from the names of the bones involved atlanto-occipital joint, glenohumeral joint, radioulnar joint
Joint Structure - Determines direction and distance of movement (range of motion or ROM). Two Methods of Classification
Range of motion of the joint = Functional classification
Anatomical structure of the joint = Structural (what it is made of) classification

5. Articulations Classifications
Range of Motion
Anatomical Structure
Joints are classified according to the manner in which the adjacent bones are bound to each other, determines how freely the bones can move
Bony
Fibrous
Cartilaginous
Synovial capsule
Synarthrosis: little to no movement
Synostosis- Suture - bony
Gomphosis - fibrous
Synchondrosis- cartilage
Amphiarthrosis: slightly moveable
Syndesmosis - fibrous
Symphyses - cartilage
Diarthrosis: freely moveable
Synovial joints -

6. Range of Motion: SYNARTHROSES
SYNARTHROSES (“syn”-together; “arthro”-joint)
Little to no movement
Very strong
Edges of bones may touch or interlock; no joint cavity
Four (4) types of synarthrotic joints
FIBROUS Structure
Suture – fibrous to bony
Synostosis - bony- occurs when fibrous material is replaced by bone in an adult it becomes
Gomphosis - fibrousy
Fibrous joints contain a thin layer of dense fibrous connective tissue uniting bones of the skullin anadult-
CARTILAGE Structure
Synchondrosis –cartilaginous

7. Synarthroses- FIBROUS
SYNOSTOSIS / SUTURE –fused fibers/cartilage to bone
Bones interlocked; adds strength of decreases incidence of fracture
Are bound by dense fibrous connective tissue
Immovable
Metopic suture of skull
Epiphyseal LINES of long bones- cartilage to bony suture
Fusion of 1st rib and sternum
GOMPHOSIS (“gomph=nail; osis=bolt”)
Fibrous connection (periodontal ligament)
Binds teeth to socket
collagen fibers attach tooth to jawbone
allows the tooth to move some under the stress of chewing

8. SYNCHONDROSIS - Cartilage
“Syn” - junction bound by
“Chondro” – cartilage
“Osis”- process, condition
Rigid hyaline cartilage bridge - sternum / ribs
Epiphyseal plate of hyaline cartilage in growing long bones, temporary
Epiphyseal line - permanent

9. Range of Motion: AMPHIARTHROSES
More movable than synarthrosis
Stronger than freely movable joint
SYNDESMOSIS (syn-with; desmos- band)
Fibrous interosseous membrane or ligament
Longer collagenous fibers
Less movable: distal tibia/fibular
More movable
radius/ulna- allows for supination/pronation
SYMPHYSES
Bones separated by fibrocartilage; compressible and resilient -acts as shock absorber and permits limited movement; Designed for strength and flexibility
Intervertebral disc
Symphyses pubis

10. Range of Motion: SYNOVIAL JOINTS
DIARTHROSIS (“dia”- through, apart) = very moveable
At ends of long bones
Complex; Most familiar and common
Comprised of a synovial joint which contains synovial cavity lined with a synovial membrane separating articulating bones
Associated synovial joint structures
Cartilages - Cushion the joint (Fibrocartilage- meniscus)
Fat Pads - Superficial to joint capsule; Protect articular cartilages
Ligaments - Support, strengthen joints
Sprain – ligaments with torn collagen fibers
Tendons - Attach to muscles around joint- Help support joint
Bursae - where two body parts move against one another and THERE IS NO JOINT TO REDUCE THE FRICTION
Ex: Cushion areas where tendons or ligaments rub against skin or bone
Pockets of synovial fluid
Bursitis: Inflammation of the bursae

11. Articular cartilages: Hyaline cartilage
Prevent bones from touching and grinding against one another
Remnant of endochondral bone formation.
Absorbs compression

12. Articular (joint) Capsule
Encloses the synovial cavity, unites the articulating bones. Has two parts: fibrous capsule and synovial membrane.
Fibrous outer capsule - dense irregular connective tissue; tough but flexible.
Synovial inner membrane made of areolar connective tissue w/ elastic fibers and adipose
Membrane fibroblasts secrete synovial fluid from filtration of blood flowing thru capillaries
Fluid has “egg white” consistency; hyaluronic acid is formed in the synovial membrane cells. Thins as the fluid is warmed.
Fills cavity- occupies all free spaces within the capsule
Lubricates joint- “weeping lubrication” – movement of joint squeezes fluid in and out of cartilage
Nourishes articular cartilages
Contains phagocytes
Exercise important component-
warms fluid, movement enables articular cartilage to absorb nutrients and remove waste
Shock absorption

13. Accessory Structures ACCESSORY LIGAMENTS
Extracapsular ligaments lie outside the articular capsule; joint articulation and stability
Patellar ligament
Intracapsular ligaments occur within the articular capsule.
Provide stability but allow a larger range of motion
Anterior cruciate ligament (ACL)
Posterior cruciate ligament (PCL)
Accessory Structures
ARTICULAR DISCS (MENISCUS). Pads of fibrocartilage within the synovial joint.
Contribute to congruence (how well bones fit together at the articulation and the closeness of the articulating elements.)

14. “Cracking” Sound in the Joint
When force is applied to a synovial joint it separates the articulating surfaces creating a reduction in pressure within the cavity.** In this low pressure atmosphere some of the dissolved gases present in the fluid (mostly nitrogen and CO2,) are released and form a bubble or cavity. The bubble collapses on itself resulting in a clicking or popping sound. This is known as cavitation.
When joints move, tendon’s position changes and moves slightly out of place. Hear a snapping sound as the tendon returns to original position. Ligaments also tighten making a similar sound.
**Separation increases volume lowers pressure –Boyles Law V P

15. Synovial Joints Classified by Dynamic Motion Linear movement (gliding)
Angular movement
Rotation
Classified by Planes (Axes) of Dynamic Motion
Monaxial (1 axis)
Biaxial (2 axes)
Triaxial (3 axes)
Specific categories of synovial joint movements based on its motion and plane
Plane/gliding – monoaxial; linear
Hinge – monoaxial; angular
Pivot – monoaxial; rotation
Condylar / Ellipsoid –biaxial; angular
Saddle - biaxial; angular
Ball & socket –triaxial; angular, rotation

17. “MOVEMENT” of Synovial Joints
Gliding (Planar): Surface of one bone moves back and forth and side to side over a flat surface.
Angular: Increase or decrease in the angle between bones
Flexion/extension
Hyperextension
Abduction/adduction
Circumduction
Rotation (Pivot): Bone revolves around its own longitudinal axis
Pronation/supination
Special: occurring only at particular joints
Inversion/eversion
Dorsiflexion/plantar flexion
Protraction/retraction
Elevation/depression

18. MOVEMENT: I. Gliding/Planar
Surface of one bone moves back and forth and side to side over a flat surface. No angular or rotational motion
Movements limited by tight joint capsules.
Action of one joint is slight but combination of many joints allows for considerable movement

19. Increase or decrease in the angle between bones
Flexion: decrease in the angle between articulating bones
Lateral flexion: bending at the waste sideways to either right or left. Occurs in the frontal plane at the intervertebral joints.
Extension: increase in the angle between two articulating bones
Lateral flexion
Bends vertebral column from side to side
MOVEMENT: II. Angular

20. II. Angular
Hyperextension: continuation of extension beyond the anatomical position. Prevented at some joints by the shape of the articulating bones and the ligaments associated with the joint.
Flexion, hyperextension and lateral flexion of vertebral column

21. II. Angular Abduction: movement of a bone AWAY from the midline.
Adduction: movement of a bone TOWARD the midline.

22. II. Angular No special joint category
Circumduction: movement of the distal end of a part of the body in a circle.
Circular motion without rotation
No special joint category

23. MOVEMENT: III. Rotation
A bone rotates around its own long axis. Relative to longitudinal axis of body.
Occurs at pivot and ball-and-socket joints
Medial rotation: (inward rotation) Rotates toward axis - midline
MOVEMENT: III. Rotation
Lateral rotation: anterior surface of a bone or a limb
limb is turned away from the midline.
Rotates away from axis
Supination: movement of the forearm at the proximal and distal radioulnar joints so that the palm is turned anteriorly
Pronation: movement at the same joints as in
supination, but so that the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly

24. IV. Special Movements
Inversion: movement of the soles medially at the intertarsal joints so that they face each other.
Eversion: movement of the soles laterally at the intertarsal joints so that they face away from each other.
Dorsiflexion: bending the foot superiorly at the ankle; lifting toes
Plantar flexion: bending the foot at the ankle toward the plantar surface; pointing toes

25. IV. Special Movements
Elevation/Depression: upward/downward movement of a body part. The jaw and the shoulders.
Protraction/Retraction: movement anteriorly in transverse plane/return to anatomical position of a body part. Jaw, chest
Opposition: movement of the thumb so that it touches the fingers.

26. Synovial Joint PLANES/AXIS
NON-AXIAL
Gliding - Flattened/slightly curved faces- limited motion
MONAXIAL - motion in one (1) planes
Hinge- Angular motion in a single plane
Pivot - Rotation only
BIAXIAL -motion in two (2) planes
Condylar – (oval articular face within a depression)
Saddle -Two concave, straddled
TRIAXIAL - motion in three (3) planes
Ball-and-socket - Round articular face in a depression

27. CATEGORY: “PLANE” Non-axial Vertebral column Intercarpal joints
Intertarsal joints
Clavicle/sternum

28. CATEGORY: Hinge Joint CATEGORY: Pivot Joint
Concave surface of one bone articulates with and fits into the convex surface of another bone.
Monaxial- moves freely in one plane (angular)
Flexion or extension
Ex: Knee, elbow, ankle, joints.
CATEGORY: Pivot Joint
Round or pointed surface of one bone fits into a ring formed by another bone and a ligament.
Bone spins on its longitudinal axis
Rotation-- Monaxial
atlanto-axial joint (“no” movement of head)
Radioulnar jointt

29. CATEGORY: Condylar (Ellipsoid))
Oval-shaped condyle of a bone fits into an elliptical cavity of another bone
Flexion, extension, adduction, abduction,
Biaxial movement – moves in two planes
wrist -radiocarpal joint
Meta-carpophalangeal joint
Meta-tarsophalangeal joint
CATEGORY: Saddle Joint
Articular bones are shaped like saddle and rider
Flexion, extension, abduction, adduction
Biaxial
Examples:
Trapezium of carpus - at the thumb
Sternoclavicular joint

30. CATEGORY: Ball-and-Socket Joint
Ball-shaped surface of a bone fits into the cup-like depression of the second bone.
Most moveable: Flexion, extension, abduction, adduction, rotation, circumduction.
Triaxial
Ex: Shoulder and hip joints
The Shoulder Joint- glenohumeral joint
Allows MORE MOTION; the LEAST STABLE
Between head of humerus and glenoid cavity of scapula
Shoulder Separation
Dislocation of the shoulder joint
Shoulder Muscles (Rotator Cuff)
The Hip Joint - coxal joint
Strong ball-and-socket diarthrosis
Wide range of motion

32. The Elbow Joint A stable hinge joint
With articulations involving humerus, radius, and ulna
Major supporting structure: Biceps brachii muscle

33. The Knee Joint A complicated hinge joint
Transfers weight from femur to tibia
Articulations of the knee joint
Two femur–tibia articulations
At medial and lateral condyles
One between patella and patellar surface of femur
Seven Major Supporting Ligaments
Patellar ligament (anterior)
Two popliteal ligaments (posterior)
Anterior / posterior cruciate ligaments (inside joint capsule)
Tibial collateral ligament (medial)
Fibular collateral ligament (lateral)
Good Animation:

34. Anterior Right Leg
Posterior Right Leg

35. Intervertebral Articulations
C2 to L5 spinal vertebrae articulation
Permit small movements associated with flexion and rotation of the vertebral column
Intervertebral Ligaments
Bind vertebrae together
Stabilize the vertebral column
Intervertebral Discs are pads of fibrocartilage used to separate vertebral bodies
Damage to Discs
Slipped disc
Bulge in anulus fibrosus
Invades vertebral canal
Herniated disc
Nucleus pulposus breaks through anulus fibrosus
Presses on spinal cord or nerves

36. Synovial Joints Injuries Dislocation (luxation) Subluxation
Articulating surfaces FORCED OUT OF POSITION
Damages articular cartilage, ligaments, joint capsule
Subluxation
A PARTIAL dislocation

37. Effects of Aging on Articulations
Degenerative Changes
Arthritis
All forms of rheumatism that damage articular cartilages of synovial joints
Osteoarthritis
Gouty arthritis
Rheumatoid arthritis

38. “Allopurinal” used to treat condition
Osteoarthritis
Caused by wear and tear of joint surfaces, or genetic factors affecting collagen formation
Generally in people over age 60
Degeneration of cartilage, no involvement of synovial membrane
After joint is stationary for a time, pain at first movement that diminishes with continued movement
Gouty Arthritis
Inability to convert uric acid (waste product of DNA and RNA metabolism) to urea results in urate crystals which build up in joints. As joint moves, bones rub against crystals damaging articular cartilages resulting in severe inflammation and pain.
Form within synovial fluid
Bones can fuse
Occurs in middle-aged men with an abnormal gene
Can result from diuretic medications
“Allopurinal” used to treat condition

39. Rheumatoid Arthritis
Autoimmune disorder where white blood cells attack articular cartilages
Synovial membrane thickens and adheres to articular cartilages. Fluid accumulates in joint capsule leading to deterioration of cartilages. Joint begins to ossify.
Inflammation, swelling , severe pain
Deformation of extremities
Steroids used to treat the inflammation.

41. Other Disorders
Lyme disease (Lyme arthritis) Bacterial infection transmitted by deer ticks. Common symptoms are rash, fevers, chills, headache, stiff neck. joint stiffness, joint pain. First associated with children in Lyme, Connecticut 1970.
Joint stiffness and pain generally occur in the later stages of the disease and most often in one or both knees
Ankylosing spondylitis (“ankylos” fused) (‘spondylos”-vertebrae) (“itis” - inflammation) Syndrome of unknown cause that affects joints between the vertebrae and between the sacrum and hip bone.
Chronic inflammatory disease; treat with anti-inflammatory medications such as ibuprofen, physical therapy and in severe cases surgery.
Ankle sprains –
ligament collagen fibers become torn
Most common joint to be sprained or fractured. Treatment includes “RICE”: rest, ice, compression, elevation. 41

43. Aging and Joints Decreased production of synovial fluid
Thinning of articular cartilages
Loss of ligament length and flexibility
Arthroscopy: joint examination using instruments the size of a pencil that allows the use of tiny instruments and a tiny microscope. Small incision through which repairs can be made including removal of torn cartilages of the knee.
Arthroplasty: replacement of a joint. Hip, knee and shoulder are commonly replaced. Articular elements are replaced by plastic/stainless steel. 43