Knee not back to normal in 3 weeks after drain/shot may mean a cartilage tear per md. drain/shot caused this? i did nothing. i am not paying for mri.

Usually not. . .: If the drainage procedure was not traumatic ie bloody nor painful, it is highly unlikely the procedure caused you any negative effect. Commonly when a steroid injection fails to resolve the issue some other underlying cause such as an internal derangement of the joint or some systemic issue is producing the symptoms. Laboratory evaluation of the joint fluid may point to some underlying condition.