The Joints

A joint is a place at which two or more bones meet in the skeleton of the body. This place is called articulation.

Fibrous or fixed or immovable joints

Immovable joints have fibrous tissues between the bones. Such immovable joints are also found in the form of sutures. They are found between the bones of the skull (suture) and between the facial bones except at the joint of mandible.

Slightly immovable or cartilaginous or partially moveable joints

There is a pad of fibrous-cartilage between the ends of the bones making up the joint which allows very slight movement. Example: joint of ribs and sternum.

Movable or synovial joints

Between two bones, there is a synovial cavity filled with synovial fluid. It lubricates the joints. They are again divided into different types which are as follows,

Ball and socket joints: In these joints, femur has a ball-like spherical end called head which fits into a cup like depression of the other bone called acetabulum. It helps in the free movement of bones. Example: shoulder joint and hip joint.

Hinge joints: In these joints, one bone is movable on another bone which remains fixed. In this joint, the bones move like a door or the lid of a box moving on a hinge (180^o). Example: elbow, knee, etc.

Pivot or rotatory joints: In these joints, one bone shows the rotary movement on another bone which remains fixed. Examples: joint between atlas and axis vertebrae.

Gliding joint: In these joints, there is a slight gliding movement of one bone over another, usually through interposition of a pad of cartilage. Example: joint between carpels in wrist , tarsals in the ankle, etc.

Relation between bone and muscles

In our body, movement is brought about by the combined effect of skeletal system and muscular system. The muscles connected with the skeleton are called skeletal muscles. Such muscles are connected with bone directly or by the means of a connective tissue called tendon. We know that in our body, movement is conducted by movable joints.