Just had an x ray done on my left knee. Findings are: There is a suprapatellar joint effusion. Tibial spines are mildly prominent and there is mild narrowing in the medial compartment of the knee. Impression: 1. Suprapatellar joint effusion, no fracture. 2. Mild narrowing in the medial compartment of the knee. I don't really understand and what can cause it. I haven't fell or damaged it in anyway.