Bruce G. Stewart

• Marieb (2004) Chapter 8

Related Human Anatomy Coloring Book Assignments

Lecture Outlines

I. Definition and Basic Classification

A. Definition - Joints are points of contact between bones, between cartilage and bones, or between bones and teeth.

1. Arthrology is the study of joints

B. Basic classification of Joints: Structural and Functional Classifications

1. Structural classification - based on the presence or absence of a space between the articulation bones (joint cavity) and the type of connective tissue that binds the joint together.

a. Fibrous: there is no joint cavity and the bones are held together by fibrous connective tissue.

b. Cartilaginous: there is no joint cavity and the bones are held together by cartilage.

c. Synovial: there is a joint cavity and the bones forming the joint are united by a surrounding articular capsule and often by accessory ligaments.

2. Functional classification: takes into account the degree of mobility the joint allows.

a. Synarthrosis: an immovable joint

b. Amphiarthrosis: a slightly movable joint

c. Diarthrosis: a freely movable joint

II. Specific Types of Joints

A. Fibrous joints - bones are held together by fibrous connective tissue; no joint cavity; may be functionally classified as synarthrotic or amphiarthrotic.

1. Sutures - these are “seams” where the bones are joined by a thin layer of dense fibrous connective tissue, found only in the skull.

a. The connective tissue becomes ossified in adult forming a rigid immovable joint-synarthrotic joint.

b. Synostoses is usually the term used following ossification of the joint - bony junction.

c. Example: Coronal suture between the frontal bone and the parietal bones.

2. Syndesmoses: the bones are joined by a cord (ligament) or sheet (interosseous membrane) of fibrous tissue.

a. The joint is classified in this text as synarthrotic, but many do classify the joint as amphiarthrotic.

b. Example 1: Distal ends of the tibia and fibula - Tibiofibular joint – ligament

c. Example 2: Longitudinal connection between the radius and ulna - interosseous membrane

3. Gomphoses: a cone-shaped peg that fits into a socket. The short periodontal ligament surrounds the tooth and cements it into the alveolar socket.

a. Classified as a synarthrotic joint.

b. Example: Roots of teeth in the alveolar processes of skull

B. Cartilaginous joints: bones are held together by cartilage; no joint cavity; may be classified as synarthrotic or amphiarthrotic.

1. Synchondrosis: two bones are separated by hyaline cartilage.

a. Classified as a synarthrotic joint.

b. Example 1: epiphyseal (growth) plate region of a child’s bone with epiphysis and diaphysis separated by hyaline cartilage. Following ossification the of the hyaline cartilage the joint becomes a synostosis similar to what occurs with the sutures of the skull.

c. Example 2: joint between the first rib and the manubrium of the sternum.

2. Symphysis: two bones separated by their articular (hyaline) cartilage with a fibrocartilage pad or plate between.

a. classified as an amphiarthrotic joint because it permits slight flexibility.

b. Example: pubic symphysis between the two pubic bones of the pelvic girdle and the Intervertebral disc between the adjacent vertebrae.

C. Synovial Joints: bones not bound together; separated by a synovial cavity; all diarthrotic or freely moving joints.

1. General structure:

a. Articular cartilage: glassy-smooth articular cartilage (of hyaline cartilage) covers the surfaces of the articulating bones but does not bind the bones together.

• reduces friction and wear
• provides a small amount of cushioning to protect the ends of the articulating bones

b. Joint cavity or synovial cavity: a cavity filled with synovial fluid separating the articulating bones.

c. Articular capsule: surrounds a synovial joint, encloses the synovial cavity, and unites the articulating bones.

• made up of the synovial membrane internally and the fibrous capsule outer layer.
• the fibrous capsule consists of dense irregular cartilage attached to the periosteum of the articulating bones
• the flexibility of the capsule allows mobility of the joint, whereas the tensile strength of the cartilage protects against dislocation.

d. Synovial membrane: a inner layer of the articular capsule composed of areolar (a type of loose connective) tissue and covers all internal joint surfaces that are not hyaline cartilage. The cells secrete synovial fluid.

e. Synovial fluid: a viscous fluid that fills the synovial or joint cavity.

• thins during joint activity
• provides the lubrication between the cartilages
• weeping lubrication forces fluid into and out of the cartilages during movement
• nourishes the cells of the cartilage
• contains phagocytic cells - cleaners of cellular debris and microbes

f. Reinforcement:

• intrinsic or capsular ligaments: a thickened area of the fibrous capsule.
• extracapsular ligaments: lie outside the articular capsule
  • an example is the fibular collateral ligament of the knee joint.
• intracapsular ligaments: occur within the articular capsule but are excluded from the synovial cavity as they are covered by synovial membrane; examples are the cruciate ligaments of the knee joint.
• articular discs or menisci: fibrocartilage pads separating the articular surfaces of the articulating bones.
  • stabilize the joint
  • provides cushioning between bones
  • reduces friction during movement
  • Example - fibrocartilage pads on top of tibia in knee joint (the often injured "cartilage" of the knee).

2. Types of synovial joints – first name given is from textbook, followed by names found elsewhere in literature

a. Plane or Gliding joints (arthrodia)

• articulating surfaces usually flat
• side-to-side motion only
• non-axial (No motion around an axis)
• Example: Intermediate patellofemoral joint between patella and patellar surface of femur, intercarpal and intertarsal joints, verticular articular processes.

b. Hinge joints (ginglymus)

• convex surface of one fits concave surface of other
• motion in one plane -- monaxial
• Examples: Lateral and medial tibiofemoral joints between condyles of femur, menisci and condyles of tibia, elbow and interphalangeal joints.

c. Pivot joints (Trochoid)

• rounded, pointed, or conical surfaces of one fits within a ring formed partly by another bone & partly by a ligament
• rotation is primary motion -- monaxial
• Example: Axis/Atlas, and proximal radioulnar joint

d. condyloid joints (Ellipsoidal)

• oval-shaped condyle of one bone fits into an elliptical cavity of another bone
• side-to-side and back-and-forth motions -- biaxial
• Example: Radiocarpal (Wrist) joints, and metacarpophalangeal (Knuckle) joints

e. saddle joint (sellaris)

• like a rider sitting in a saddle
• similar to ellipsoidal joint in motion -- biaxial
• Example: Carpometacarpal joints of the thumb

f. ball-and-socket joint (Spheroid)

• name describes form clearly
• allows for complete range of motion
• triaxial
• Examples: head of femur in acetabulum (hip joint), head of humerus in glenoid cavity (shoulder joint)

3. Structures Associated with some Synovial Joints

a. Bursae and Tendon Sheaths: a friction reducer between structure around a joint; a flattened fibrous sac lined with synovial membrane with synovial fluid inside.

• bursae (bursa - singular) - a flattend fibrous sac lined with synovial membrane and containing synovial fluid
  • found in high stress areas such as the shoulder joint, knee joint and others
  • Bunion: an enlarged bursa
• tendon sheath, an elongated bursa surrounding a tendon to reduce friction.
  • found in high stress areas such as the wrist and elbow
  • once inflamed, produces pain during movement (tendonitis)

4. Stability of Synovial Joints

a. Articular surfaces: play a role in determining overall movement of the joint but have limited influence on the stability of the joint.

b. Ligaments: capsules and ligament of the synovial joints unite the bones, direct movement, and prevent excessive or undesirable motion.

• dense connective tissue collogen fibers only stretch about 6% before they snap
• stretching loosens the joint.

c. Muscle tone: the most important stabilizing factor of joints.

• tendon in conjunction with muscles monitor the position of the joint and through stretch receptors and proprioceptor receptors and send sensory information to the central nervous system (CNS)
• motor stimulation is promoted by CNS to provide appropriate muscle tone to stabilize the joint in its various positions and under various stresses

5. Synovial Joint Movements - (here we revisit and expand what we have already discussed on types of synovial joints and their movements)

a. Gliding Movements

• back/forth or side-to-side
  • Example 1: movements between carpals (intercarpal joints)
  • Example 2: movements between tarsals (intertarsal joints)
  • Example 3: movements between articular processes of vertebrae (intervertebral joints)
  • Example 4) movements between heads and tubercles of ribs on bodies and transverse processes of vertebrae

b. Angular

• increases or decreases angle between bones
• flexion - decreases the < (Symbol for "angle") versus extension
  • Example 1 - movement around the elbow can bend the arm and bring the lower arm toward the biceps (flexion) or movement can straighten the arm (extension)
  • Example 2 - muscles associated with the hip joint can pull the thigh upward (as in the first movement to lift the leg for stepping up stairs) (flexion) or straighten the thigh (extension).
• abduction- movement away from midline versus adduction - movement toward midline
  • Example - muscles associated with the shoulder joint can move the arm away from body (abduction) or toward the midline of the body (adduction)

c. Rotation

• movement around bone's own long axis
• medial rotation - anterior surface of bone moves toward the midline versus lateral rotation - anterior surface moves away from the midline
  • Example 1 - rotation of femur and humerus can reposition their anterior surfaces closer to the midline or further away
  • Example 2 - rotation of head

d. Circumduction

• movement of distal end of bone in cone-shape with respect to the joint
  • Example 1 - pitching motion in baseball/softball; arms are extended at shoulder level and enscribe a circle with hands

e. Other specific names given to motions of skeletal/muscle complex

• inversion - moving the sole medially (inward) versus eversion - moving the sole outward
• dorsiflexion - foot is bent up (toward the shin) versus plantar flexion - foot and toes are bent downward
• protraction - to move a bone forward (e.g. the mandible during chewing) versus retraction to move a bone backward toward the rear
• supination - so move the forearm so that the palm of the hand faces anteriorly (or superiorly if body is horizontal) versus pronation which is to move the forearm so that the palm faces posteriorly (or down)
• elevation - to move superiorly (as in shrugging shoulders or as in biting) versus depression - to move inferiorly (as when shoulders return to original position or as in opening the mouth to eat.

5. Details of an important joint – Tibiofemoral (Knee) joint

a. General description -- Largest and most complex joint of the body. Actually consists of three distinctive joints:

• intermediate patellofemoral joint between patella and patellar surface of the femur - a gliding joint
• lateral tibiofemoral joint between the lateral condyle of the femur, lateral meniscus & lateral condyle of the tibia - a hinge joint
• medial tibiofemoral joint between the medial condyle of the femur, medial meniscus, & medial condyle of the tibia - ahinge joint

b. Components of knee joint

• anatomy of the articular capsule
  • no complete, independent capsule
  • ligamentous sheath mostly of muscle tendons or their expansions
  • some capsular fibers connect articulating bones
• anatomy of the medial and lateral patellar retinacula (retinaculum singular )
  • fused tendons of the insertion of the quadriceps femoris muscle and the fascia lata
  • strengthens the anterior surface of joint
• anatomy of patellar ligament
  • central portion of fused tendon of insertion of the quadriceps femoris muscle
  • extends from patella to tibial tuberosity
  • strengthens the anterior surface of joint
  • infrapatellar fat pad separates posterior portion of patellar ligament from synovial membrane of joint
• anatomy of oblique popliteal ligament
  • broad, flat ligament that extends from intercondylar fossa of femur to the head of the tibia
  • tendon of semimembranous muscle is superficial to the popliteal ligament
  • strengthens posterior surface of knee
• anatomy of arcuate popliteal ligament
  • lateral condyle of femur to styloid process of the head of the fibula
  • strengthens lower lateral part of the posterior surfaces
• anatomy of tibial (=medial) collateral ligament
  • broad, flat ligament on medial surface from medial condyle of the femur to medial condyle of tibia
  • crossed by several tendons (from sartorius, gracilis, semitendinous muscles)
  • supports medial surface
• anatomy of fibular (=lateral) collateral ligament
  • strong, rounded ligament on the lateral surface of joint, from the lateral condyle of femur to the head of the fibula
  • covered by tendon of the biceps femoris
• anatomy of intra-articular ligaments
  • ligaments that are located within the capsule and connect the tibia and femur
  • two ligaments: anterior cruciate and posterior cruciate ligaments
  • anterior cruciate ligament: connects just anterior of intercondylar eminence of tibia and to posterior part of medial surface of lateral condyle of the femur
    • 70% of serious knee injuries involve this ligament
  • posterior cruciate ligament: connects to the anteriomedial area near the posterior intercondylar fossa of the tibia and lateral meniscus and then to the anterior part of medial surface of the medial condyle of femur
• anatomy of the articular discs (menisci)
  • fibrocartilage discs between the tibial and femoral condyles
  • two menisci: medial meniscus and lateral meniscus
    • attached to each other and to margins of tibia
    • medial meniscus has shape of a semicircle
    • lateral meniscus is in the shape of an O
• bursae (Pl. of bursa – Gk for leather sack, or purse)
  • many of these synovial cushions that facilitate movement and reduce friction between tendons and other structures

c. common knee injuries

• rupture of tibial collateral ligament is the most common and is often associated with tears of anterior cruciate ligament and medial meniscus
• dislocated knee - most common is hyperextension of the knee

III. Homeostatic Imbalance

A. Rheumatism – general lay term that simply means a painful state of skeleton

B. Arthritis – Inflammation or degeneration of joints and adjacent parts, most often with pain, stiffness, and swelling

1. Rheumatoid Arthritis - an autoimmune disease often manifesting itself by synovial membrane inflammation (synovitis), followed by swelling & production of a pannus (a granular tissue) that erodes fibrous tissue (and sometimes the bone).

a. scar tissue follows, and in some cases ossifies and fuses bones together (ankylosis).

2. Osteoarthritis – more common than RA and is the non-inflammatory result of general wear

3. Gouty arthritis - due to excessive uric acid production which is then the deposited as sodium ureate crystals in soft tissues of joints

a. may be genetic and affects mainly middle- to older-age males

C. Bursitis and tendonitis

D. Dislocations, or luxations: displacement of bones with tearing (ligaments, tendons, etc)

E. Damage to cartilage – cartilage tears and does not repair (is avascular); if damage is to articular cartilage, high levels of wear ensue and erode eventually to bone

F. Sprains and strains

1. Ligaments are stretched and/or torn

2. May be damage to blood vessels, muscles, etc

Reminder about Textbook Study

As with other topics, your textbook has excellent presentations of the articulations of the musculoskeletal system. While you should focus on the specific material in the Notes on the Web, you should always use your textbook as a resource for illustrations and for understanding content that your notes cover.

As with all materials throughout the semester, you will have opportunities to ask questions or ask that any relevant material from your assignments be discussed in class.

Related Internet Resources

• Links....