Synovial joints

• What are synovial joints?

  They are free moving, most limbs are synovial and the movement is determined by the structure of how bones fit together.
• Reasons for different joint classifications

  1. if distal tibiafibular was synovial, we would fall over
  2. if pubic symphysis or interverval discs were fiborus, we would be stiff and unable to move.
• Synovial joint features:

  Many of our joints are complex tissues and structures that have to allow free movement and controlled movement in particular ways.

  The bone ends determine what we are able to do.
• Synovial joint structure:

  • bone ends = to move against each other
  • articular capsule = has hyaline on the ends of the bones
  • joint capsule = something to keep bones and fluids inside (wraps around whole joint)
  • joint cavity = potential space because bones don't fuse with each other
  • synovial membrane = making synovial fluids to make cavity
  • ligaments = to attach bone to bone
• What is the hyaline structure in articular cartilage?

  It covers the articular surface of the bone. The bone underneath cartilage must be smooth (subchondrial bone). This must be smooth because it will move against the neighbouring bone and resists compression.
• Why is the joint capsule a structure?

  It is made out of DFCT as a sheet that wraps around the joint so it won't rip and tear. The inner layer of this is the synovial membrane. It is a sheet of synovial cells (fluid) for lubrication. We need this joint so when the cartilage rubs over the neighbour, there is lubrication to help more around easily. The fluid has the same nutrients as blood and pushes in the cartilage to keep chorodates alive.
• Joint capsules holds bones together and different parts of it, thicker or thinner depends on what we need:

  thinner = loose and more movement and has less support and stability.

  thicker = tighter and less movement.
• We can add specific ligaments in thick bands of DFCT.
• What are ligaments?

  They connect bone to bone and made of collagen and elastin. their job is to resist movement away from themselves.
• What are the two types of ligaments?

  Capsular ligaments and Intracapsular ligaments.
• What are capsular ligaments?

  They are located in thickened bands that sit in the joint capsules. We need more support movement and restrict movement away from selves.
• Example of capsular ligament:

  Colateral ligament on either sides of the knee.
• What are the two types of colateral ligaments?

  Medial (MCL): It connects the femur to the tibula. If the leg tries to abduct, the ligament will pull and stop it (restricts it) and provides stability.

  
  

  Lateral (LCL): It connects the femur to the fibula.
• What are intracapsular ligaments?

  The ligaments seperate from the joint capsule. They are additional bands that are internal to the capsule and holds bones together.
• Example of intracapsular ligament is the cruciate ligaments of the knee.
• What are the two types of cruciate ligaments to the knee?

  Anterior (ACL): It starts from the anterior of tibia and backwards to the joint and to the posterior. It will stop the femur from slicing backwards. (stops movement posteriorly away from itself).

  
  

  Posterior (PCL): It starts from the posterior of the tibia and runs towards through the middle of the joint and attaches anteriorly to the femur. (stops the femur from sliding forward).
• Fibrocartilogenous pads are found in the intervertebral discs and are in some joints. They fill the space between bones and provide cushioning for shock absoption to send pressure. They help us to move and deepen articulations.
• What are joint movement?

  They are a range of movement (ROM), which is the type of movement you can do.
• What are joint movements determined by?

  • muscles
  • bone and shape
  • ligament location and strength
  • body surface contact
• What are the synovial joint movements?

  • Sagittal, coronal and transverse
  • Flexion, extension, abduction, adduction, rotation, circumduction.
• What are the types of synovial joints?

  • plane
  • hinge
  • pivot
  • condylar
  • ellipsoid
  • saddle
  • ball and socket
• Plane joints

  • multiaxial
  • sliding and gliding
  • flat articular surface
  • e.g intercarpal and intertarsal joints
• Hinge joints are the most common type of joint in the body and are found in the shoulder, elbow, and knee.
• Hinge joints

  • uniaxial
  • movements are flexion and extension
  • e.g ankle and elbow (humerus with ulna) and interphalangal joints
• Pivot joints

  • uniaxial
  • movement is rotation
  • e.g radioulnar joints and C1-C2 vertebrae
• Condylar joints

  • Biaxial
  • movements are flexion and extension and rotation (when flexed)
  • e.g knee and TMJ
• Ellipsoid joint

  • Biaxial
  • movements are flexion, extension, adduction and abduction
  • NO rotation
  • e.g wrist joint
• Saddle joint

  • biaxial
  • movements are flexion, extension, abduction and adduction and circumduction
  • obligatory rotation - opposition
  • e.g carpmetacarpal joint
• Ball and socket joint

  • multiaxial
  • movements are flexion, extension, abduction, adduction, circumductial and rotation
  • e.g shoulder and hip