How Our Bodies Work

The joints between bones make the movements of the bones possible. Imagine you are having breakfast: even the smallest movements, such as lifting your mug, would not be possible without joints. Lifting the mug requires the coordinated operation of joints that allow movement in various directions.

This joint has the largest articular sur­face and the most complex structure in the human body. Since the knees bear a huge load, it is very important to take good care of them. To reduce injuries, always warm them up before doing exercise or going running.

Types of joints

Joints can be grouped by the direction of movement they allow.

Ball-and-socket joint

The ball-shaped articular surface of
one rounded bone fits into the cup-like depression of another bone. It allows for movement in any direction.

Pivot joint

The articular surface is round and
the axis of rotation coincides with the longitudinal axis of the bone. The joint between the radius and the ulna in
the elbow is an example of this type.

Gliding joint

Also called a plane joint, it is formed between bones that meet at flat or near­ly flat articular surfaces. This type of joint can be found between carpal bones.

Saddle joint

The opposing surfaces are reciprocally concave-convex. It is characteristic
of the joints found between metacarpal bones.

Synovial joints

These are the most common and most
moveable type of joint in the body. The
joint is bounded by the synovial capsule.
The surface of the bones connected by
a joint is covered by cartilage that pro-
vides a smooth and slippery surface, and
synovial fluid serves to reduce friction.
The joint is stabilised by ligaments.

Hinge joint

This type of joint permits motion in a single plane. The knee joints are an example of this type.

Condyloid joint

Also called ellipsoid joint,
it can be found between the radius and the carpal bones.

Synovial joint cavity

It is filled with synovial fluid, which lubricates the cartilage and reduces friction
in the joint.