Anatomy – joints of human body

Figure 1. Characteristics of joints

Types of synovial joint:

Ball and socket joint: allow movement around multiple axes; permit flexion, extension, abduction, adduction, circumduction and rotation. (hip joint)

Hinge joint: allow movement around one axis that passes transversely through the joint, permit flexion and extension. (elbow(humero-ulnar)joint)

Pivot joint: allow movement around one axis that passes longitudinally along the shaft of the bone, permit rotation. (atlanto-axial joint)

Condylar joint: allow movements around two axes that are at right angles to each other, permit flexion, extension, abduction, adduction and circumduction. (wrist joint)

Saddle joint: allow movements around two axes that are at right angles to each other, permit flexion, extension, abduction, adduction and circumduction. (carpometacarpal joints)

Plane joint: allow sliding or gliding movements when one bone moves across the surface of another. (acromioclavicular joint)

Figure 2. Types of synovial joints

Fibrous joint:

In a fibrous joint, the bones are bound by a tough fibrous connective tissue. These joints exhibit little to no mobility.

Types of fibrous joints:

 Sutures:  sutures are fibrous joints found exclusively between the bones of the skull, where adjacent bones are linked by a thin layer of connective tissue termed a sutural ligament.

Figure 3. Coronal suture

Gomphosis: gomphoses is found in the mouth where the roots of the teeth articulate with the dental alveoli at the dentoalveolar joints. The tooth is bound into its socket by the strong periodontal ligament.

Figure 4. Gomphosis

Syndesmosis:

we have a syndesmosis, which is formed by ligaments and a strong membrane that holds two bones in place.

interosseous membrane runs between the radius and the ulna.

Figure 5. syndesmosis

Cartilaginous joint

In a cartilaginous joint, the bones are connected by a fibrocartilage or hyaline cartilage.

These joints can be subclassified into two types – synchondroses and symphyses.

synchondroses or primary cartilaginous joint where the bones are connected by hyaline cartilage. The growth plate that occur between the head and shaft of developing long bones. These joints allow bone growth and eventually become completely ossified.

joint where the bones are connected by fibrocartilage, this type of joint is found primarily along the midline of the body; for example, the

pubic symphysis, intervertebral discs between adjacent vertebrae.

Figure 6. Cartilaginous joints

There are also two other classification of joints based on the mobility and range of motion.

Mobility classification.

Diarthrosis:

Diarthrosis is a freely mobile joint. (Knee and shoulder joint)

Amphiarthrosis:

Amphiarthrosis is slightly mobile joint. (pubic symphysis and syndesmosis)

Synarthrosis:

Synarthrosis is an immobile joint. (coronal suture, gomphosis)

Range of motion classification:

Uniaxial:

Joints that can move back and forth along a single axis are called uniaxial. (Hinge and pivot joint)

Biaxial:

Joints that move about two distinct axes are called biaxial. (the condylar and the saddle joint)

Polyaxial or multiaxial:

joints that can move through all three axes are called polyaxial or multiaxial. (ball and socket joint)