Joints is a site where two more bones come together, where movements may or may not occur.
Classification of joints is done on two bases
Functionally joints are classified into three
1. Synarthrosis – immovable joints; i.e no movements are possible in these types of joints. Example include joints in skull, ribs-sternum joints etc
2. Amphiarthrosis – slightly movable joints, example are tibia – fibula joint, pubis joints etc
3. Diarthrosis – freely movable joints that is all types of movements are possible, example are hinge, pivot , ball and socket joints etc
Structurally the joints are classified according to the tissue that lies between the bones.
a) Fibrous joints – In this bones are held together by dense irregular connective tissue, there is no synovial cavity, three types of fibrous joints are
• Sutures – composed of thin layer of dense irregular connective tissue and functionally these are synarthrosis, present in the skull bones like coronal suture between parietal and frontal bone
• Syndesmoses – consist of dense layer of connective tissue and greater distance is present between the articulating surface of the bones. The layer of tissue is present in the form of ligaments and they permit limited movement , examples is distal tibiofibular joint.
• Gomphosis – in this cone shaped mouth fits into the socket, example is the root of teeth fits into their sockets (alveoli) of mandible maxillae
• Interosseuos Membrane – sheet of dense irregular connective tissue that binds the bone and allow limited movement, example is the joint between radius and ulna.
b) Cartilaginous joints – connecting material in these joints is either hyaline cartilage or fibrocartilage, lacks synovial cavity. These are of two types:
• Synchondroses – connecting material is the hyaline cartilage , example is the epiphyseal plate between the epiphyses abd diaphysis of a growing bone.
• Symphyses – the articulating bone are covered by hyaline cartilage but the main joining material is the fibrocartilage, permits slight movement. An example is the pubic symphysis between the anterior surface of the hip bones.
c) Synovial joints – there are some unique characteristic of this joint which makes it different from another joint like presence of synovial cavity between the articulating surface of the bones which makes the joint freely movable and that’s why all the synovial joints are classified as diarthrosis. A layer of hyaline cartilage is also present between the bones which is known as articular cartilage, the synovial fluid present in the synovial cavity cavity reduces friction between the bones. Synovial joints are of 6 types
• Planer joints – in this type of joint, the articulating surface is flat or slightly curved, allows side to side movements, biaxial joints because they permit movement around two axis, examples are intercarpal joints(between the carpals at the wrist), strenoclavicular joints(between manubrium of sternum and the clavicle).
• Hinge joint – the convex surface of one bone fits into the concave surface of another. These are monoaxial joints and allows only flexion and extension. Examples are knee , elbow , ankle and interphalangeal joints.
• Pivot joint – in this joint, the rounded surface of one bone fits with the ring formed surface of another bone, monoaxial joints and allows only rotation, examples are atlanto-axial joint.
• Saddle joint – in this joint, the articulating surface of bone is saddle shaped and the articulating surface surface of another bone fits into it, these are triaxial joints and permits flexion extension rotation adduction and abduction. Examples are carpometacarpal joints.
• Condyloid joint – also known as ellipsoidal joint in which the projection formed in one bone fits into the depression of another bone, biaxial joints and allows flexion extension adduction and abduction. Example are metacarpophalangeal joints.
• Ball and socket joint – in these joints, cup like shape of one bone joints with ball shaped of another bone, triaxial joints and allows extension adduction abduction rotation and flexion. Examples are the shoulder joint and the hip joints
MULTIPLE CHOICE QUESTIONS (MCQs):-
1. Which of the following is an example of syndesmoses?
A. coronal suture B. distal tibiofibular joint
c. hip joint D. intercarpal joints
2. Which of the following comes under structural classification?
A. Synchondroses B. Sutures
C. gomphosis D. all of the above
3. Which of the following movements are possible in pivot joint?
A. flexion and extension B. adduction and abduction
c. rotation D. extension flexion and rotation
4. Match the following-
1. unites the bones of skull (a) gomphosis
2. joint between two pubic bones (b) symphysis
3. joint having a cavity between (c) sutures
4.joint between teeth and bone (d) synovial joint
5. Which of the following is known as a bony joint?
A. synostosis B. symphysis
C. syndesmoses d. interosseous membrane
6. What do you mean by the movement adduction?
A. decrease in the angle between the bones
B. increase in the angle between the bones
C. movement of bone toward the midline
D. movement of bone away from the midline
7. Which of the following are the part of functional classification?
A. Ellipsoidal B. GOMPHOSIS
C. Syndesmoses D. none of the above
8. Which of the following statement is NOT true?
A. condyloid joint is triaxial
B. synovial fluid reduces friction
C. coronal suture is for parietal and frontal bone articulation
d. synostosis is a bony joint
9. Which the following is not the unique features of synovial joint?
A. Articular capsule B. articular cartilage
C. synovial fluid D. fibro cartilage
10. What is the medical terminology for the pain in joints called?
A. Chondritis B. Arthralgia
C. synovitis D. Rheumatism
1. distal tibio fibular joint
2. all of the above
4. 1 – c 2 – b 3 – a 4 – d
6. movement of the bone towards the midline
7. none of the above
8. condyloid joint is triaxial
9. fibro cartilage
Gerard J. Tortora -Principles of anatomy and physiology; edition twelfth ; page no.-: 265-277