I Had An MRI Of My Left Knee Due To

I had an MRI of my left knee due to pain w/o injury. It says I have "mild signal heterogeneity within the articular cartilage of the patella. There is also faint linear fissure within the cartilage just to the lateral side of midline." What does it mean? The orthopedic doctor I saw just said you have some arthritis and gave me a shot, which did not help at all.