I have a self-harm problem of excessively cracking, twisting and popping my index finger. At times I have even wished I could break it…for some reason I enjoy inflicting that type of pain on myself. This finger is now swollen and feels very loose…I know the cartilage is worn from my abuse. My question can this cause bone cancer and can rheumatoid arthritis effect just this one finger?

Rheumatoid arthritis almost always affects more than one joint at a time in a symmetrical manner. So, if one knee had rheumatoid arthritis, the other knee would usually also have it.

There are over 100 different kinds of arthritis though, some of which only affect one single joint. Osteoarthritis is one example of a type of arthritis that only affects one joint.