What causes arthritis in the knee i don't think i have this b/c i didn't injured myself the pain is awful front of knee & back pain?

Disc: It is possible that you knee pain is coming from you lumbar spine or low back. Most back pain resolves on its own. However, there are many over the counter medications that can help with these problems. If it persist and is unbearable see your primary care doctor.

Osteoarthritis: The most likely reason is ligament or cartilage damage. This leads to excessive sliding and grinding of the joint. This results in osteoarthritis which in this case is degenerative wear and tear of the knee joint.

See your doctor: You could have a host of issues that could cause your knee pain, could be bursitis, tendonitis, arthritis, ligament issues, meniscal injury, sciatica etc. So you may want to see an orthopedic pain specialist that can tell you what is going and help you with the latest treatments or exercise therapies available.