classification and structure of joints

• what is a joint?

  • also called articulations
  • points of contact between bones and cartilage and bones, and teeth and bones of the body which link the skeletal system into a functional whole
  • bones are rigid and therefore movement can only occur at joints
  • the structure of a joint determines the type of movements that may occur
  • some joints e.g., sutures of the skull – do not allow for much movement, instead, they form sutures that protect the organ e.g., the brain
• arthrology


  study of joints
• kinesiology


  study of motion of the body
• cartilage


  a resilient, strong connective tissue that is less hard and more flexible than bone
• ligament


  a tough band of connective tissue that attaches bone to bone
• tendon 


  a tough band of connective tissue that attaches muscles to bones
• functional classification of joints

  refers to the degree of motion a joint permits

  1. synarthroses
  2. amphiarthrosis
  3. diarthroses (synovial)
• synarthroses (no movement)

  • the bones are close together and may even overlock
  • extremely strong joints - located where movement between bones must be prevented
• amphiarthrosis (little movement)


  permits more movement than a synarthrosis but is much stronger than a freely movable joint. the articulating bones are connected by collagen fibers or cartilage (cartilaginous joints), 2 types:

  1. syndesmosis - the articulating bones are connected by a ligament e.g. distal articulation between the tibia and fibula
  2. symphysis - the articulating bones are separated by a wedge or pad of fibrocartilage e.g. connection between the two pubic bones (the punic symphysis)
• diarthrosis (free movement)


  also known as synovial joints, they permit a wider range of motion, typically located at the end of long bones
• structure of a synovial joint (knee)

  • joint cavity/ joint space
  • joint (articular) capsule
  • fibrous capsule
  • synovial membrane - lines the articular cavity
  • synovial fluid - nourishes and lubricates the articular cartilage, shock absorber to distribute compressive forces
  • articular hyaline cartilage - reduce friction during movement of the joint
  • may contain intra-articular structures such as menisci (knee), articular disc (TMJ) and articular labrum (shoulder)
• classification of a synovial joint

  1. ball and socket – e.g. hip joint, shoulder joint
  2. hinge - permits movement in one plane, usually flection and extension e.g. knee joint
  3. ellipsoid/condyloid - contains a convex surface which articulates with a concave elliptical cavity e.g. metatarsophalangeal joint 
  4. saddle - opposing articular surfaces with a reciprocal concave-convex shape e.g. carpometacarpal joints
  5. pivot - allows for rotation only e.g. distal radioulnar joints
  6. plane - the articular surfaces are relatively flat, allowing bones to glide over one another e.g. subtalar joint
• structural classification of joints

  • this refers to the type of connective tissue that binds the joint together and whether there is a synovial cavity between the joints or not 
  • structurally, joints are classified as:

  1. fibrous joints 
  2. cartilaginous joints 
  3. synovial joints
• fibrous joints

  • in fibrous joints, bone ends are held together by fibrous or collagenous connective tissues without synovial cavity between them
  • these are strong joints that inhibit movement
  • in general, these are synarthroses
• cartilaginous joints

  • bone ends are held together by cartilage, and they do not have synovial cavity between them
  • these are strong joints with minimal movements only
  • most cartilaginous joints are amphiarthrotic, but some are also synarthrotic
• synovial joints

  • bone ends separated by synovial cavity which allows for great deal of movement
  • all synovial joints are diarthrotic
  • synovial joints predominate the limbs
  • it has synovial cavity, articular cartilage, synovial capsule or articular capsule and reinforcing ligaments; same has articular discs, menisci, and bursae
• accessory structures

  • fat pad – commonly superficial to the joint capsule, protect the articular cartilages.
  • ligaments:
  •  accessory ligament are localised thickenings of the capsule.
  • extracapsular ligaments interconnect the articulating bones and pass across the outside of the capsule.
  • intracapsular ligaments help to prevent excessive movement that might damage the joint.
  • tendons – may limit the range of motion and provide mechanical support.
  • fascia – help to maintain shape and position of muscles and allow adjacent muscles to move past each other