Hi, All these are MRI findings of traumatic knee injury: 1 - Medial meniscus is the cushion present between tibia and femur, a tear of meniscus is either stable or unstable, tear can be either repairable or not, peripheral tears can heal while the central can not 2- Loose bodies could be either a piece of bone, meniscal fragment, calcification or osteophyte. Loose bodies can obstruct knee flexion or extension 3- Signal abnormality could be anything that is different from normal signal pattern at the particular site, it indicates trauma, an avulsion or anything 4- Joint effusion occurs as a result of trauma or inflammation,but in your case it appears to be the result of hemorrhage Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Rohan Shanker Tiwari, Orthopedic Surgeon