This is a contiguous series of sagittal MRI slices of the left knee in a 25y old man. Two images are presented side by side; the one on the left is similar to a T1-weighted image, the one on the right is similar to a T2-weighted image in which the signal from fat has been suppressed. Occasionally, as an aid to identifying labelled structures, an axial image indicating the plane of the sagittal images has been been placed below them. You can look at the video frame by frame and try to identify the lettered structures. The answers will be revealed when you click on the appropriately labelled drop-down arrows below the image.