Joints

Published on 11/03/2015 by admin

Filed under Orthopaedics

Last modified 11/03/2015

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2 Joints

A joint is formed where two or more bones meet and is classified as being synovial, fibrous or cartilaginous in nature.

The main types of joints found in the body are classified as synovial joints.

Synovial joints (diarthroses)

Features of a typical synovial joint (Fig. 2.1)

Fig. 2.1 Typical synovial joint (coronal section).

A – Fibrous capsule

B – Synovial membrane

C – Articular hyaline cartilage

D – Synovial fluid.

All synovial joints have a fibrous capsule, a synovial membrane lining the capsule which secretes synovial fluid and a protective layer of articular hyaline cartilage covering the bone articular surfaces.

Articular hyaline cartilage covers the articular surfaces.

A fibrous capsule surrounds the joint.

Synovial membrane lines the joint, except where articular hyaline cartilage is found.

A lubricant film of synovial fluid is secreted into the joint cavity by the synovial membrane.

Ligaments strengthen the joint capsule. These may be separate from the capsule or may blend with it.

Movement occurs at the joint but the amount varies with the type of synovial joint.

Nerves and blood vessels supply the joint.

Intracapsular structures may be present, e.g. tendons, ligaments, joint discs, pads of fat.

Movements of the joints

Flexion –

bending the joint, i.e. decreasing the angle between the bones.

Extension –

straightening the joint, i.e. increasing the angle between the bones.

Abduction –

to move away from the midline.

Adduction –

to move towards the midline.

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