Joints

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Joints
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Classification of Joints

• Functional classification
• (Focuses on amount of movement)
• Synarthroses (immovable joints)
• Amphiarthroses (slightly movable joints)
• Diarthroses (freely movable joints)
• Structural classification
• (Based on the material binding them and presence
  or absence of a joint cavity)
• Bony fusion
• Fibrous
• Cartilagenous
• Synovial

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Table of Joint Types
Functional across Structural down Synarthroses (immovable joints) Amphiarthroses (some movement) Diarthroses (freely movable)
Bony Fusion Synostosis (frontalmetopic suture epiphyseal lines)
Fibrous Suture (skull only) -fibrous tissue is continuous with periosteum Gomphoses (teeth) -ligament is periodontal ligament Syndesmoses -ligaments only between bones here, short so some but not a lot of movement (example tib-fib ligament) Syndesmoses -ligament longer (example radioulnar interosseous membrane)
Cartilagenous (bone united by cartilage only) Synchondroses -hyaline cartilage (examples manubrium-C1, epiphyseal plates) Sympheses -fibrocartilage (examples between discs, pubic symphesis
Synovial Are all diarthrotic
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Fibrous joints

• Bones connected by fibrous tissue dense regular
  connective tissue
• No joint cavity
• Slightly immovable or
• not at all
• Types
• Sutures
• Syndesmoses
• Gomphoses

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Sutures

• Only between bones of skull
• Fibrous tissue continuous with periosteum
• Ossify and fuse in middle age now technically
  called synostoses bony junctions

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Syndesmoses

• In Greek ligament
• Bones connected by ligaments only
• Amount of movement depends on length of the
  fibers longer than in sutures

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Gomphoses

• Is a peg-in-socket
• Only example is tooth with its socket
• Ligament is a short periodontal ligament

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Cartilagenous joints

• Articulating bones united by cartilage
• Lack a joint cavity
• Not highly movable
• Two types
• Synchondroses (singular synchondrosis)
• Sympheses (singular symphesis)

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Synchondroses

• Literally junction of cartilage
• Hyaline cartilage unites the bones
• Immovable (synarthroses)
• Examples
• Epiphyseal plates
• Joint between first ribs costal cartilage and
  manubrium of the sternum

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Sympheses

• Literally growing together
• Fibrocartilage unites the bones
• Slightly movable (amphiarthroses)
• Resilient shock absorber
• Provide strength and flexibility
• Hyaline cartilage on articular surfaces of bones
  to reduce friction
• Examples
• Intervertebral discs
• Pubic symphysis of the pelvis

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Synchondroses and sympheses
Also pubic symphsis
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Synovial joints

• Include most of the bodys joints
• All are diarthroses (freely movable)
• All contain fluid-filled joint cavity

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General Structure of Synovial Joints

• Articular cartilage
• Hyaline
• Spongy cushions absorb compression
• Protects ends of bones from being crushed
• Joint (synovial) cavity
• Potential space
• Small amount of synovial fluid

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General structure of synovial joints (cont.)

• 3. Articular (or joint) capsule
• Two layered
• Outer fibrous capsule of dense irregular
  connective tissue continuous with periosteum
• Inner synovial membrane of loose connective
  tissue (makes synovial fluid)
• Lines all internal joint surfaces not covered by
  cartilage

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General structure of synovial joints (cont.)

• 4. Synovial fluid
• Filtrate of blood
• Contains special glycoproteins
• Nourishes cartilage and functions as slippery
  lubricant
• Weeping lubricatioin
• 5. Reinforcing ligaments (some joints)
• Capsular (most) thickened parts of capsule
• Extracapsular
• Intracapsular

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General structure of synovial joints (cont.)

• 6. Nerves
• Detect pain
• Monitor stretch (one of the ways of sensing
  posture and body movements)
• 7. Blood vessels
• Rich blood supply
• Extensive capillary beds in synovial membrane
  (produce the blood filtrate)

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General structure of synovial joints
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Some joints

• Articular disc or
• meniscus
• (literally crescent)
• Only some joints
• Those with bone
• ends of different
• shapes or fitting poorly
• Some to allow two kinds of movement (e.g. jaw)
• Of fibrocartilage
• Examples knee
• TMJ (temporomandibular
  joint)
• sternoclavicular joint

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Bursae and tendon sheaths

• Contain synovial fluid
• Not joints but often associated with them
• Act like ball bearings
• Bursa means purse in Latin
• Flattened sac lined by synovial membrane
• Where ligaments, muscles, tendons, or bones
  overlie each other and rub together
• Tendon sheath
• Only on tendons subjected to friction

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Bursae and tendon sheaths
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Joint stability

• Articular surfaces
• Shape usually plays only minor role
• Some deep sockets or grooves do provide stability
• Ligaments
• Usually the more, the stronger the joint
• Can stretch only 6 beyond normal length before
  tear
• Once stretched, stay stretched
• Muscle tone
• Constant, low level of contractile force
• Keeps tension on the ligaments
• Especially important at shoulders, knees, arches
  of foot

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Movements allowed by synovial joints

• Gliding
• Angular movements hor i the angle between two
  bones DO TOGETHER
• Flexion
• Extension
• Abduction
• Adduction
• Circumduction
• Rotation
• Special movements

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Special movements

• Pronation
• Supination
• Dorsiflexion
• Plantar flexion
• Inversion
• Eversion

• Protraction
• Retraction
• Elevation
• Depression
• Opposition

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Joint movements pics (from Marieb, 4th ed.)
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Synovial joints classified by shape(of their
articular surfaces)

• Plane (see right)
• Hinge (see right)
• Pivot
• Condyloid
• Saddle
• Ball-and-socket

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Shoulder (glenohumeral) joint
Selected synovial joints

• Stability sacrificed for mobility
• Ball and socket head of humerus with glenoid
  cavity of scapula
• Glenoid labrum rim of fibrocartilage
• Thin, loose capsule
• Strongest ligament coracohumeral
• Muscle tendons help stability
• Disorders

Rotator cuff muscles add to stability
Biceps tendon is intra-articular
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Elbow joint

• Hinge allows only flexion and extension
• Annular ligament of radius attaches to capsule
• Capsule thickens into
• Radial collateral ligament
• Ulnar collateral ligament
• Muscles cross joint
• Trauma

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Wrist joint Two major joint surfacesSeveral
ligaments stabilize

• Radiocarpal joint
• Between radius and proximal carpals (scaphoid and
  lunate)
• Condyloid joint
• Flexion extension adduction, abduction,
  circumduction
• Intercarpal or midcarpal joint
• Between the proximal and distal rows of carpals

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Hip (coxal) joint

• Ball and socket
• Moves in all axes but limited by ligaments and
  deep socket
• Three ext. ligaments screw in head of femur
  when standing
• Iliofemoral
• Pubofemoral
• Ischiofemoral

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• Acetabular labrum diameter smaller than head of
  femur
• Dislocations rare
• Ligament of head of femur supplies artery
• Muscle tendons cross joint
• Hip fractures common in elderly because of
  osteoporosis

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Right hip, AP view
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Knee joint

• Largest and most complex joint
• Primarily a hinge
• Compound and bicondyloid femur and tibia both
  have 2 condyles
• Femoropatellar joint shares joint cavity
• At least a dozen bursae
• Prepatellar
• Suprapatellar

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• Lateral and medial menisci
• torn cartilage
• Capsule absent anteriorly
• Capsular and extracapsular ligaments
• Taut when knee extended to prevent hyperextension

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• Patellar ligament
• Continuation of quad tendon
• Medial and lateral retinacula
• Fibular and tibial collateral ligaments
• Called medial and lateral
• Extracapsular
• Oblique popliteal
• Arcuate popliteal

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Cruciate ligaments

• Cross each other (cruciate means cross)
• Anterior cruciate (ACL)
• Anterior intercondylar area of tibia to medial
  side of lateral condyl of femur
• Posterior cruciate
• Posterior intercondylar area of tibia to lateral
  side of medial condyl
• Restraining straps
• Lock the knee

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Cruciate ligaments
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Knee injuries

• Flat tibial surface predisposes to horizontal
  injuries
• Lateral blow multiple tears
• ACL injuries
• Stop and twist
• Commoner in women athletes
• Heal poorly
• Require surgery

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Ankle joint

• Hinge joint
• Distal tibia and fibula to talus
• Dorsiflexion and plantar flexion only
• Medial deltoid ligament
• Lateral ligaments 3 bands
• Anterior talofibular
• Posterior talofibular
• Calcaneofibular
• Anterior and posterior tibiofibular (syndesmosis)

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Right ankle, lateral view
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Temporomandibular joint (TMJ)

• Head of mandible articulates with temporal bone
• Disc protects thin mandibular fossa of temporal
  bone
• Many movements
• Demonstrate movements together
• Disorders common

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Sternoclavicular joint

• Saddle joint
• Only other example is trapezium and metacarpal 1
  (thumb), allowing opposion
• Sternum and 1st costal (rib) cartilage articulate
  with clavicle
• Very stable clavicle usually breaks before
  dislocation of joint
• Only bony attachment of axial skeleton to
  pectoral girdle
• Demonstrate movements together

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Disorders of joints

• Injuries
• Sprains
• Dislocatios
• Torn cartilage
• Inflammatory and degenerative conditions
• Bursitis
• Tendinitis
• Arthritis
• Osteoarthritis (DJD degenerative joint
  disease)
• Rheumatoid arthritis (one of many autoimmune
  arthritites)
• Gout (crystal arthropathy)