Joints and its classification

• A joint is connection in the skeleton between any of its rigid component parts, whether bone or cartilages.
• Joints are constructed to allow movement, provide mechanical support and allow for growth.
• An articulation or an arthrosis is the same as a joint.
• Arthrology is the science concerned with the study of joints.
• Kinesiology is the study of movements involving certain joints
• Joints Classification

  1. Structural features
  2. Degree of mobility
• Structural features

  1. Fibrous joints
  2. Cartilaginous joints
  3. Synovial joints
• Degree of mobility

  1. Immovable or synarthrodial joints
  2. Partially movable or amphiarthrodial joints
  3. Freely movable or diarthrodial joint
• Fill in the blank

  A) Fibrous joints

  B) Cartilageous joints

  C) Synovial joints

  D) Collagen

  E) Synovial membrane

  F) Synovial fluid

  
• Fibrous joints are found between 2 bones of intramembranous origin
• Fibrous joints are usually immovable.

  There are 4 types:

  1. Sutures
  2. Schindylesis
  3. Syndesmosis
  4. Gomphosis
• Sutures

  • are found only between the bones of the skull.
  • In the foetal skull the sutures are wide apart to allow a slight degree of movement between the skull bones during its passage through the birth canal.
  • After birth, the sutures become quite rigid over a period of time, allowing no movement between the articulating surfaces
• Types of sutures

  1. Squamous suture
  2. Sutura limbosa
  3. Serrated suture
  4. Denticulate suture
  5. Plane suture
• Squamous suture

  • the articulating bones simply overlap obliquely.
  • E.g. suture between temporal & parietal bones
• Sutura limbosa

  • the overlapping edges are ridged or serrated.
  • E.g. suture between temporal & parietal bones
• Serrated suture

  • has saw-tooth projections on the surfaces of connecting bones
  • E.g. sagittal suture
• Denticulate suture

  • has interlocking surfaces shaped like dovetails.
  • Its edges have tooth-like processes that widen toward the ends.
  • E.g. Lambdoid suture.
• Plane suture

  • Two flat surfaces are in contact, where there is simple apposition of contiguous rough surfaces.
  • E.g. palatine processes of the maxilla or between the horizontal plates of the palatine bones
• Schindylesis (wedge & groove type of suture)

  • It is a tongue & groove type of joint where one bone fits into the channeled groove of another.
  • E.g. Vomer of nasal septum fitting into the sphenoid bone.
• Syndesmosis

  • It is partially movable fibrous joint.
  • The bony components are farther apart and is united by a fibrous interosseous membrane.
  • They persist throughout life.
  • The bony surfaces are united by inter-osseous ligament.
  • E.g. inferior radio-ulnar joint, ligamentum flava of vertebra.
• Gomphosis

  • It is a unique joint in the form of peg & socket articulation between the roots of the teeth and the alveolar process of jaw bones.
  • Fibrous tissue (periodontal ligament) anchors the tooth securely in the socket.
• Applied anatomy

  • Mobility of the joint indicates a pathological state affecting the supporting ligament of the teeth
• Bones are united by hyaline or fibrocartilage.

  There are 2 types :

  1. Primary cartilaginous joint
  2. Secondary Cartilaginous joint
• Primary cartilaginous joint

  • The joint is a temporary union replaced by bone when growth ceases.
  • They develop between bones of endochondral origin.
  • e.g. epiphyseal plate of long bone.
• Secondary Cartilaginous joint

  • Partially movable type where opposing are covered hyaline with cartilage but separated from each other by intervening fibrous tissue or fibrocartilage.
  • It is a permanent type of cartilaginous joint.
  • It is always found in the midline.
  • e.g. Intervertebral joint, symphysis pubis
• Fill in the blank

  A) Plane suture

  B) Squamous suture

  C) Sutura limbosa

  D) Serrated suture

  E) Denticulate suture

  F) Schindylesis

  G) Gomphosis

  H) Syndesmosis

  
• Fill in the blank

  A) hyaline

  B) fibrocartilage

  C) covered

  D) Immovable

  E) Rarely

  F) Always

  
• Synovial joints

  • They are freely movable joints
  • are typically found in all joints of the limbs.
• Characteristic features of synovial joints

  1. The articular surface
  2. Joint cavity
  3. Capsular ligament
  4. Synovial membrane
  5. Disc
• The articular surfaces

  • The articular surfaces of the opposing bones are covered by hyaline cartilage.
  • It is avascular & alymphatic.
  • It is nourished by diffusion from the adjacent bone and by synovial fluid within the joint.
• Joint cavity

  • a joint cavity or space always exist between the articular surfaces of the opposing bones
• Capsular ligament

  • always covers the joint like a fibrous sleeve and attaches to the circumference of both bones.
  • It completely encloses the joint cavity.
  • Collagen fibers run in the capsule in all directions to resist torsion or twisting.
  • Some of the capsular ligaments are thickened to form ligaments of the joint.
  • Strong ligaments are often found at the sides of the joint.
• Synovial membrane

  • is a vascular loose connective tissue that lines the inner surface of the joint capsule and the part of the bone within the joint cavity but does not line the articular surface.
  • It secretes an oily fluid "synovium", which is a lubricating fluid into the joint cavity and also nourishes the articular cartilage.
• Disc

  • The joint cavity is sometimes partially or completely subdivided by fibro-cartilaginous disc or meniscus into two compartments.
  • The periphery of the disc is attached to the joint capsule.
  • Its function is to ensure perfect contact between the moving surfaces in any position of the joint and helps to maintain perfect lubrication.
  • It allows 2 types of movement, one for each compartment.
  • E.g. temporo-mandibular joint and knee joint.
• Fill in the blank

  A) The articular surface

  B) Hyaline cartilage

  C) Articular disc

  D) Joint cavity

  E) Synovial membrane

  F) Articular capsule

  
• Classification of synovial joint

  According to the number of articulating surfaces

  1. Simple – has only one pair of articulating surfaces. E.g. joints of fingers.
  2. Compound – has more than one pair of articulating surfaces. E.g. elbow joint
  3. Complex – the joint cavity is partially or completely divided by a disc or meniscus. e.g. knee joint, temporo-mandibular join
• Fill in the blank (Classification of synovial joint)

  A) Simple

  B) Compound

  C) Complex

  
• Classification of synovial joint

  According to the number of axes

  1. Uniaxial joint
  2. Bi-axial joint
  3. Multi-axial joint
• Classification of synovial joint

  According to the number of axes

  1. Uniaxial joint

  • Axis may be vertical or horizontal
  • has one degree of freedom.
  • E.g. pivot joint (vertical axis); hinge joint (horizontal axis)
• Classification of synovial joint

  According to the number of axes

  2. Bi-axial joint

  • There are two axes which are at mutual right angles
  • has two degrees of freedom.
  • E.g. ellipsoidal joint; saddle joint