Is grinding the main cause of jaw joint problem?

Jaw pain: Its one of the problems which can cause jaw pain.

No: There can be many causes- trauma, poor bite, clenching, grinding, dental work, etc. Could be stress, but in all, grinding may or may not be part of a tmj/tmd problem.

One of causes: Causes of TMJ syndrome are not completely understood.. Causes may include, misalignment (malocclusion) of or trauma to the teeth or jaw, teeth grinding (bruxism),, poor posture, stress or anxiety, arthritis or other inflammatory musculoskeletal disorders, excessive gum chewing. Treatment can be complex and beyond the scope of this answer. See a TMJ expert for guidance.