Exercise 3.5
Look at the picture given below (Fig. ). Carefully observe the various poses of classical and folk dances of India. Can you identify which joints are involved? Also, what type of movement each joint allows? Exploration|Grade 
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
The dance poses between them use all four joint types the chapter names — ball and socket, hinge, pivot, and (unmoving) fixed.
Shoulder — ball and socket joint. The rounded top of the upper arm bone sits in a shallow hollow of the shoulder bone, so the raised, spread and circling arms of almost every pose can move forward, backwards, sideways and in circles. This is the freest joint in the body and the reason arm positions carry so much of the expression.
Hip — ball and socket joint. Gives the turned-out, sideways and circular leg movements of the classic half-sitting stance.
Elbow — hinge joint. Bends and straightens the forearm in one direction only, like a door hinge — used whenever the arm is folded in or extended out.
Knee — hinge joint. Bends and straightens in one plane for the deep bent-knee stance; the kneecap, a small bone, protects the joint while it is loaded.
Ankle — hinge-type movement. Up-and-down movement of the foot for the flat-footed stamping of the footwork.
Neck — pivot joint. The skull is connected to the backbone by a pivot joint, letting the head move side to side like a doorknob turning in its socket — the signature head movement of Indian classical dance.
Wrist and fingers. Bending and partial rotation shape the hand gestures.
Backbone. Not a single joint but a column of vertebrae with a cartilage disc between each pair, cushioning them and allowing the torso to bend and twist without injuring the spinal cord.
Skull — fixed joints. Its flat bones stay locked together throughout, keeping the brain safe however vigorously the body moves.
In every case the joint only permits the movement; the chapter is explicit that joints cannot move bones on their own — muscles contract and pull on the bones through tendons, and the movement appears at the joint.