 In our past tutorials covering various aspects of MRI knee, we have discussed individually in details about structures and their pathology. Today I will just summarize step by step how to interpret any knee MRI that comes to you for reporting so that there are chances of you making no mistake. For any joint a format makes life much easier and if followed there are less chances of missing any pathology but you have to follow certain rules and go step by step. Needless to say plane radiograph does really not give us a clear idea about what is happening inside the knee joint and MRI reveals certain details like things like the bone marrow, articular cartilage, menisci, tendons, ligaments, soft tissue muscles in much greater detail. The basic sequences that we need universally are proton density FATSAT, non-FATSAT, T2FFE to look for blood products and also T1 to look for fracture lines. This is a format that I follow step by step while reporting an MRI knee. Number one, I see the ligaments. The four basic ligaments that I step by step T are the anterior cruciate ligament, which are the intra-capsular extraseinovial ligaments and then I come to the collaterals. The anterior cruciate ligament has two bundles and through medial postural lateral bundle. For seeing any ligament pathology we have to look for three things. Number one, we look for ligament contour. Is there any disruption of fibers or any abnormal signal? Next we come to the posterior cruciate ligament. It has a femoral and tibial attachment which may not be seen in the same plane which is normal. After that I go, I see the medial collateral ligament, see its continuity, signal changes and surrounding structures look for edema here and there. In case of the medial collateral ligament we have to see the superficial fibers and deep fibers and look for pathology. Then we come to the lateral collateral ligament which is usually not seen rather in one single plane. In case of redundant lateral collateral ligament where some pathology is suspected, we may see it in one single plane. Next in the format comes my menisci. When we talk of meniscus, we discuss about the shape of the menisci, any abnormal shape, any abnormal signal intensity reaching any, reaching the articular surfaces. The shape of the menisci typically in sagittal sequences have a bow pie appearance and then as we go along then the horns, the two horns triangular shaped horns come. We look for at the free edge of the horns, we look at the articular, the tibial surface, articular surface, the femoral articular surfaces. We look for signal changes where we can classify the meniscal tabs. A few things that we have to look for specifically is the meniscal root. The root is best seen in coronal view and we have to correlate with the axial as well as the sagittal planes for root pairs. Here is one example of an abnormal signal intensity which is traversing right up to the articular surface and therefore being classified as tear, another vertical tear. Next in the format comes joint space and articular cartilage. Articular cartilage intact looks like this beautifully in a PD non-faxated image. We have to typically examine the articular surface throughout in the weight bearing and non-weight bearing surface. This is an example of cartilage loss in the weight bearing surface. We have to measure the cartilage defect. We can also have osteocondrial defects. We have to measure them. We have to see whether they are separated or not, their exact location. After that, next in the format comes the anterior extensor mechanism. In the sagittal planes, we look at the quadriceps tendon, the position of patella, whether it is normal, the patella tendon and its attachment, any pathology at its tibial attachment in the tibial tubercle region. And in the axial plane, we clearly see the retro patella cartilage and various gradings of chondromalacia patella, as we already know, can be seen in these sequences. Whether there is a full thickness cartilage loss, whether the underlying patella shows changes. This is an example where we see that the cartilage is completely gone. Here, the patella is itself very deformed, a case of chronic patella dislocation. Also in the axial sequence, we see the patella retinocular, the medial and the lateral retinocular. In case of patella dislocations, they are commonly torn. And that has to be described and seen in these sequences. We also, in the anterior extensor mechanism, we look for synovial plica, whether they are thickened or not. Many times, plica syndrome occurs. The plica are responsible for clinical symptoms of the patient. So, presence of an abnormal plica need to be reported. After this comes a very important area, the posterior lateral corner. Posterior lateral corner injuries are usually seen along with posterior cruciate ligament tears. Clinician usually has a doubt about posterior lateral corner and gives us an idea and enables us to see that area more clearly because of their clinical doubt. The basic, most important things that we see are the fibular collateral ligament, lateral gastronomious tendon, popliteus tendon, popliteofibular ligament, the posterior joint capsule, archivate ligament. This is just one example of pathology where we have significant PLC corner injury with edema in the popliteus muscle, the popliteus musculotendinous junction. The popliteus tendon actually doesn't reach and join where it's supposed to with significant edema and torn popliteofibular ligament. In fact, the lateral collateral ligament also is torn here. This is an example where there is significant capsule injury with fluid outside the capsule seen here. Undetected, posterior lateral corner injuries is very, very grievous because many a times when the surgeon just repairs the anterior cruciate ligament and does not pay attention to the posterior lateral corner because it is not reported, this may lead to ACL graft failure. So, PLC corner injury detection by the MRI specialist is a must. Next, we come in our format to discuss the posterior medial corner. This is a readily identifiable but very underappreciated area. Importance of seeing this and identifying the pathology is that if unidentified, it results in a condition called anterior medial rotational instability. The main structures that we see here are semi-membranous tendon, oblique popliteal ligament, posterior oblique ligament, posterior horn of the medial meniscus and the medial collateral ligament. This is an example of injury where there is significant edema in the posterior medial joint capsule, there is significant fluid separating the superficial and the deep fibres of the medial collateral ligament. Lastly, there are few things which we need to see before completing our MRI report. We look for bone edema pattern, any trabecular lines, effusion, anovitis and anything else that may exist outside our format. So, after following this format finally we come to our impression. The impression should be very crisp, clear, not descriptive, in fact very assertive. So, the take home message for anyone reporting MRI knee should be, please read the prescription before starting the report. It really helps you to exactly pinpoint the diagnosis. In case of doubtful cases, please don't be lazy, call the patient for examination or communicate with the referring clinician who has actually examined the patient. Follow the format step by step and avoid using the term suggested clinical correlation as far as possible.