Joints!

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Joints!

• 3 types of joints if we classify by function
  (i.e., by the degree of movement possible)
• Diarthroses
• Freely moveable joints
• Shoulder, knee, hip, elbow, interphalangeal,
  tarsal, and carpal joints
• Amphiarthroses
• Slightly moveable joints
• Intervertebral discs, costosternal joints, pubic
  symphysis
• Synarthroses
• Joints with little or no movement
• Skull sutures, mental symphysis, teeth in
  sockets, 1st costosternal joint.

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Joint Classification

• We can also classify joints by structure
• Synovial joints
• Bones separated by a joint cavity lubricated by
  synovial fluid enclosed in a fibrous joint
  capsule.
• Shoulder, hip, elbow, knee, carpal,
  interphalangeal

How would we classify these joints functionally?
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Joint Classification

• Fibrous joints
• Bones held together by collagenous fibers
  extending from the matrix of one bone into the
  matrix of the next.
• No joint cavity
• Skull sutures, teeth in joints, distal radioulnar
  joints tibiofibular joints

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Joint Classifications

• Cartilaginous joints
• Bones held together by cartilage no joint cavity
• Epiphyseal plates of long bones, costosternal
  joints, pubic symphysis, intervertebral discs

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Structure and Function

• Joints are designed for their function.
• Lets look at sutures as our 1st example
• Name 4 sutures!
• What function do you suppose sutures are designed
  for?

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Structure and Function

• Lets look at some symphyses.
• What kind of joint is a symphysis? What kind of
  movement is possible?
• Name a symphysis! (an obvious one is in the
  picture)
• What connects the bones in these joints?

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Structure and Function

• Now lets talk about synovial joints.
• How do they differ from the previous 2?
• 5 main structural characteristics
• Articular cartilage
• What kind of cartilage is it? (H _ _ _ _ _ _ )
• Where do we find it?
• What does it do?

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Structure and Function

• Articular capsule
• 2 layered. Surrounds both articular cartilages
  and the space btwn them.
• External layer is made of dense irregular CT is
  continuous w/ the perisoteum.
• Inner layer is a synovial membrane made of loose
  connective tissue.
• It covers all internal joint surfaces except for
  those areas covered by the articular cartilage.

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Structure and Function

• Joint (Synovial) Cavity
• The potential space within the joint capsule and
  articular cartilage
• Synovial Fluid
• A small amount of slippery fluid occupying all
  free space w/i the joint capsule
• Formed by filtration of blood flowing thru
  capillaries in the synovial membrane
• Synovial fluid becomes less viscous as joint
  activity increases.

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Structure and Function

• Reinforcing Ligaments
• What kind of tissue are they?
• What do you suppose their function is?
• Double-jointed-ness results from extra-stretchy
  ligaments and joint capsules. Is this
  necessarily a good thing?

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Other Synovial Structures

• The knee and hip joints have cushioning fatty
  pads btwn the fibrous capsule and the synovial
  membrane or bone.
• Discs of fibrocartilage (i.e., menisci) which
  improve the fit btwn bone ends, thus stabilizing
  the joint.
• Found in the knee, jaw, and sternoclavicular
  joint.
• Bursae are basically bags of lubricant - fibrous
  membrane bags filled w/ synovial fluid. Often
  found where bones, muscles, tendons, or ligaments
  rub together.

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Types of Synovial Joints

• Plane joints
• Articular surfaces are flat and allow short
  slipping or gliding movements.
• Intercarpal and intertarsal joints
• Hinge joints
• A cylindrical projection of one bone fits into a
  trough-shaped surface on another (like a hotdog
  in a bun)
• Movement resembles a door hinge.
• Elbow joint ulna and humerus Interphalangeal
  joints

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Type of Synovial Joints

• Pivot joints
• Rounded end of one bone protrudes into a ring
  formed by another bone or by ligaments of that
  bone.
• Proximal radioulnar joint
• Atlas-axial joint
• Condyloid joints
• Oval articular surface of one bone fits into a
  complementary depression on another.
• Radiocarpal joints
• Metacarpophalangeal joints

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Types of Synovial Joints

• Saddle joints
• Each articular surface has convex and concave
  areas. Each articular surface is saddle-shaped.
• Carpometacarpal joints of the thumbs.
• Ball-and-Socket joints
• Spherical or semi-spherical head of one bone
  articulates with the cuplike socket of another.
• Allow for much freedom of motion.
• Shoulder and hip joints.

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The Knee

• Largest and most complex diarthrosis in the body.
• Primarily a hinge joint, but when the knee is
  flexed, it is also capable of slight rotation and
  lateral gliding.
• Actually consists of 3 joints
• Patellofemoral joint
• Medial and lateral tibiofemoral joints
• The joint cavity is only partially enclosed by a
  capsule on the medial, lateral, and posterior
  sides.

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The Knee

• The lateral and medial condyles of the femur
  articulate with the lateral and medial condyles
  of the tibia.
• Btwn these structures, we have the lateral and
  medial menisci.
• Anteriorly, the patellar ligament binds the tibia
  (where?) to the inferior portion of the patella.
  The superior portion of the patella is then
  connected to the quadriceps femoris muscle

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The Knee

• At least a dozen bursae are associated with the
  knee.
• Multiple ligaments are present.
• The fibular collateral ligament extends from the
  lateral epicondyle of the femur to the head of
  the fibula.
• The tibial collateral ligament connects medial
  epicondyle of the femur to the medial condyle of
  the tibial shaft and is also fused to the medial
  meniscus.
• Both of these ligaments prevent excessive rotation

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The Knee

• The anterior and posterior cruciate ligaments are
  also very important.
• ACL connects the anterior intercondylar area of
  the tibia to the medial side of the lateral
  femoral condyle.
• Prevents forward sliding of the tibia and
  hyperextension of the knee.
• PCL connects the posterior intercondylar area of
  the tibia to the lateral side of the medial
  femoral condyle.
• Prevents backward displacement of the tibia or
  forward sliding of the femur.

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Clinical Conditions

• Arthritis describes about 100 different types of
  inflammatory or degenerative joint diseases.
• Osteoarthritis
• Most common arthritis.
• Normal joint use prompts the release of
  cartilage-damaging enzymes. If cartilage
  destruction exceeds cartilage replacement, were
  left with roughened, cracked, eroded cartilages.

• Eventually bone tissue thickens and forms spurs
  that can restrict movement.
• Most common in C and L spine, fingers, knuckles,
  knees, and hips.

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Clinical Conditions

• Rheumatoid arthritis
• Chronic inflammatory disorder
• Marked by flare-ups
• Autoimmune disease.
• Body creates antibodies which attack the joint
  surfaces
• The synovial membrane can inflame and eventually
  thicken into a pannus an abnormal tissue that
  clings to the articular cartilage.
• The pannus erodes the cartilage and eventually
  scar tissue forms and connects the 2 bone ends.
  This scar tissue can later ossify, fusing the
  bones together. This is known as ankylosis.

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Clinical Conditions

• Gouty arthritis
• When nucleic acids (such as ????) are metabolized
  uric acid is produced. Normally uric acid is
  excreted in the urine.
• If blood uric acid rises due to decreased
  excretion or increased production, it may begin
  to form needle-shaped crystals in the soft
  tissues of joints.
• Inflammation ensues causing painful arthritis.