Joints And Movement

The joints in the body are the places where two bones are joined together. The joints are strong enough to withstand jerks. The ends of bones are covered with soft cartilage. It acts as a shock absorber and reduces friction between the bones. Cartilage is also present in some parts of the body that are not as hard as the bones, for example the upper part of the ear. The bones are held together at the joints by strong, stretchy bands called Ligaments. There are many joints in the body. The joints are of three types, depending on the types of movement they allow—immovable, slightly movable and freely movable.

The bones in the skull (except the lower jaw bone) do not allow any movement. The joints between the ribs and the breast bone allow only  slight movement. Most of the joints in the human body are freely movable joints. These freely movable joints are of four main types, depending on the type of movement they allow.

Immovable or fixed joints :

The joints do not allow any movement between the bones. For eg : the bone of skull are interlocked with each other and held together by fibrous cartilage, which do not allow any movement.

Slightly Movable joints: 

These joints allow very little movement due to the presence of a pad of flexible cartilage between their ends. For example, joints present between adjacent vertebrae in the backbone or spine allow only slight movement. This kind of joint provides more support.

Freely movable joints :

1.  Hinge Joint: 

  The elbow, knee and finger joints allow movement in one plane only, that is, up and down, or backward and forward, like the hinges of a door. Such joints are therefore called hinge joints. We have hinge joints in our elbows, fingers, knees and toes.

2. Ball and Socket Joint:

The shoulder and hip joints allow movement in all directions. In such joints, the end of one of the bones is round like a ball. It fits into a hollow part (or socket) in the other bone.

3. Pivot Joint: 

The neck joint also allows movement in all directions. It allows you to move your head up and down, left and right and also to rotate it. In such joints, one of the bones ends in a rounded or conical surface that fits into a dent in the other bone. Such a joint is called a pivot joint.

4. Gliding Joint:

The wrist or ankle joints have flattened ends of bones that can move ( or glide) against each other, These joints allow side to side as well as backward and forward movement. The vertebrae also have similar joints that allow slight movement. Gliding joints are found between the wrist and the carpals and between the ankle and the tarsals.

Six types of movements of Joints :-

Extension :- This kind of movement occurs when angle of movement is changed. For example, the elbow when a shot is fired. When a high jumper takes off , the knee takes off stretches.

Flexion :- Bending a joint. This occurs when a joint angle is decreasing for eg, when he does a biceps curl, the elbow flexes. The leg flexes as it prepares to kick a ball.

Ball and socket joints also allow flexion and extension.

Adduction :- Movement towards the midline of the body. This occurs at the hip and shoulder, returning the arms and legs back to their original position from a jumping jack movement or when swimming breast stroke.

Abduction :-  Abduction moves the limb laterally away from the midline of the body, while abduction is the opposing movement that brings the limb toward the body or across the midline.

Circumduction :- Circumduction is the movement of a body region in a circular manner, in which one end  of the body region being moved stays relatively stationary while the other end describes a circle. It involves the sequential combination of flexion , adduction, extension and abduction at a joint.

Rotation :- Rotation  is the circular movement of a joint or muscle that allows the bodily part to move in a circular manner. The two types of rotational movements are internal rotation and external rotation.