Would I qualify for SSI Disability

I have Osteoarthritis in my hip. This condition is also affecting my knee and lower back. I am being seen by a doctor. I am working full time as a mechanic. (it is a quick lube and tire shop), but my doctor doesn't think I will be able to continue working there much longer due to the condition of my knee. I am in a lot of pain most of the day and sometimes can not put much weight on my knee. I have kept working because I simply can't afford not to.