Osteoarthritis of the knee is one of the leading causes of disability in the USA. It develops slowly and the pain it causes worsens over time. Once you have tried physical therapy, and steroid injections that failed, one treatment option is a procedure called viscosupplementation or gel injections. Platelet-rich plasma (PRP) therapy uses your own blood, concentrates its healing properties, and it is reinjected back into the affected area such as the knee, elbow, wrist, and shoulder.