Anatomy And Disorders Of The Knee

The human body consists of many joints that also vary in type. A joint is defined as the articulation of any two or more bones. Different types of joints are so classified depending upon the range of motion they permit. For example, Shoulder joint allows complete rotation of the arm whereas the Elbow joint allows only flexion and extension. The above-mentioned example exhibits how two different joints on the same part of body (arm) permit different range of motion. In case of the shoulder, rotation of the arm is possible because the head of humerus (bone in the upper part of arm) articulates with the socket of shoulder girdle. The socket formed by Glenoid Cavity and the articulating ball in the form of head of humerus make up the ball and socket joint that permits motion along the entire circumference because of the ball moving in all directions inside the socket. Similarly, the elbow joint functions like a hinge used in door. Just the way a hinge permits motion of the door/window along only one line, similarly the elbow joint permits only flexion and extension (along one line) motions. There are other types of joints too but it is the hinge joint that we would concentrate on for a simple reason that our joint-of-interest is Knee and it happens to be of hinge type.