Chapter 9: Synovial Joints and Joint Injuries

What are synovial joints?

• bones separated by a joint cavity

• include most joints in body

• diarthroses (free mobile)

• basic features?

  • articular capsule and joint cavity

  • synovial fluid

  • articular cartilage

  • ligaments, nerves and blood vessels

What is the double layered articular capsule (joints capsule)?

• outer fibrous layer

  • DRCT

  • strengthen joints prevent bones pulled apart, hold in synovial fluid

• inner synovial membrane

  • areolar connective tissue

  • covers internal joint surfaces not covered by cartilage

  • produce synovial fluid

What is the articular cartilage?

• hyaline cartilage on bone surface at joint

• function

  • reduce friction during movement

  • acts as cushion absorb joint compression

  • prevents damage to articulating ends of bones

• avascular

What is the joint cavity?

• space between articulating bones

• lines by synovial membrane secreting fluid

• viscous, oily substance

• functions:

  • lubricates articular cartilage

  • nourishes the chondrocytes

  • acts as shock absober

What are the ligaments?

• DRCT

• connect bone to bone

• stabilize, strengthen and reinforce synovial joints

What are the sensory receptors and blood vessels?

• numerous

• detect painful stimuli, report on movement and stretch

What are the tendons?

• DRCT

• not part synovial joint itself

• attach muscle to bone

• help stabilize

What are the bursae?

• fibrous, saclike structures containing synovial fluid

• lined internally by synovial membrane

• found synovial where bones, ligaments, muscles, skin or tendons rub together

• connected to or separate from joint cavity

• alleviate friction

What are tendon sheaths?

• elongated bursae

• wrap around tendon where friction is excessive

• common in wrist and ankle

What are the menisci?

• deep to articular capsule within knee joint

• c-shaped fibrocartilage pads on top of tibial condyles

• cushioning between articular surfaces

• change shape to conform to articulating surfaces

• partially stabilize joint medially and laterally

What are the shape classifications?

• plane

  • flat articulation, side-to-side movement in single plane

  • simple, least mobile

  • tarsals, carpals, vertebrae

• hinge

  • convex surface within concave depression

  • hinge of door

  • elbow, middle phalangeal

• pivot

  • rounded surface sits into ligament ring

  • rotation longitudinal axis

  • proximal radius/ulna (elbow)

• condylar

  • oval, convex shape (condyle) articulating with concave surface (fossa)

  • wrist, ankle, jaw, knee, proximal phalanx

• saddle

  • convex and concave surface resembling saddle shape

  • thumb

• ball-and-socket

  • spherical head bone fitting into cuplike socket

  • 3 planes of movement, most mobile

  • hip and shoulder, not a bony socket

What are the movements of synovial joints?

gliding, flexion, extension, hyperextension, lateral flexion, circumduction, rotation, dorsiflexion, plantar flexion, eversion, inversion, protraction, retraction

What is the shoulder joint?

• most stability due to rotator cuff muscles

  • SITS - supraspinatus, infraspinatus, teres minor, subscapularis

  • work as group hold humerus in glenoid cavity

  • tendons encircle joint and fuse with articular capsule

What are some joint injuries?

• tibial collateral ligament - leg forcibly abducted

• fibular collateral ligament - medial side of knee struck

• ACL - hyper extended

• PCL - hyper flexed

• Meniscus - trauma and/or overuse

• Unhappy triad: tibial collateral ligament, medial meniscus, ACL

  • lateral blow to knee, abducts and laterally rotates leg

What is a sprain?

• stretching/tearing of ligaments without fractur or dislocation

• twisting foot, over inversion

• fibers lateral ligament stretched or torn

• localized swelling and tenderness anteroinferior to lateral malleolus

What are some shoulder dislocations?

• common due to instability

• shoulder separation - acromioclavicular joint dislocation

  • pain abducted more than 90

  • acromion appearing prominent

• glenohumeral dislocation - abducted humerus struck hard

  • shoulder flattened and squared-ff

  • humeral head anterior and inferior to glenohumeral joint capsule

What is arthritis?

• group inflammatory/degenerative diseases of joints

• joint swelling, pain and stiffness

What is gouty arthritis?

• middle-aged or older males

• increased levels or uric acid

What is osteoarthritis?

• degenerative joint condition in older individuals

• wearing down of articular cartilage

• fingers, knuckles, hips, knees, and shoulders most affected

What is rheumatoid arthritis?

• younger to middle-aged adults, often women

• autoimmune disorder

• starts with synovial membrane inflammation