Euflexa did nothing for knee pain. should i try cortisone?

You could: Euflexa and other injections like it, it suppose to relief pain by helping to repiar of the cartilage in the knee it a while to work, and the damage to the cartlage is advance it will do anythings.

Yes but...: I find that these treatments are less likely to work if you have severe knee arthritis on a standing knee x-ray. For example if you have bone on bone arthritis on x-ray there is about a 50% chance that injections like euflexa, orthovisc, synvisc, (hylan g-f 20) will work. Even if you have severe arthritis, it is reasonable to try a cortisone injection. However only expect temporary relief at best.