Tendonosis is the degeneration or breakdown of the connective tissue and collagen within your tendon. It commonly occurs at either your medial or lateral epicondyles (small bones on the edge of your elbow) or on the back of your wrist.
It can occur at any point where the tendon inserts onto the bone. Tendonosis can be due to micro-trauma, ageing and poor blood flow. Micro-trauma can be when there is repetitive forces pulling where the tendon originates in the bone.