Joints

1
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.

2
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?
3
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

4
Joint Classifications

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

5
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?

6
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?

7
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?

8
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.

9
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.

10
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?

11
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

13
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.

15
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.

16
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

17
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

18
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.

19
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.

20
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.