This is Barry Belosis, one of the musculoskeletal radiology fellows at Stanford University. 26-year-old mountain biker presents with left knee and hip pain, concerned for Lyme disease. The patient in this case presented with this MRI knee without contrast. In here, we can see some Mog edema signal of the quadriceps fat pad right here, and also this lobulated cystic lesion that was described as arising from the Baker's cyst, but it's not well depicted on this sagittal imaging. We also look for any signs of edema signal in the half-ass fat pad, which will be here, or any large joint effusion, which the patient does not have, or any synovial thickening to assess for synovitis. On a different patient, this is an MRI knee with and without contrast. Synovitis is any inflammatory process that affects the synovium. It can be from the joint or tendon sheath or bursa. Contrast-enhanced MRI is the preferred tool. When we evaluate for synovitis, we look at the half-ass fat pad. In this patient, we have some edema signal in the half-ass fat pad, which has been associated with synovitis, however non-specific. We look for a degree of joint effusion, which is large on this patient, and we try to assess for synovial thickening on this non-contrast imaging. It is limited, as we cannot completely discern between the synovium and the fluid itself, so contrast-enhanced imaging, such as on this patient, is a preferred tool for evaluating synovial thickness, and the grading system of synovitis is based on the degree of synovial thickening. Here, we can see a large joint effusion with synovial thickening, consistent with synovitis. On a different patient, again here, we have MRI knee with and without contrast. We can see this non-contrast axial T2 fat sat imaging, demonstrating large joint effusion, with likely some synovial thickening here in the posterior margin. This is better characterized here on our T1 fat sat and post-contrast imaging. In here, we can see the synovial thickening pretty clearly, and it touches here in the posterior margin, and also circumferentially, consistent with synovitis. MRI cannot differentiate septic from non-septic arthritis with accuracy, but it can suggest a difference between the two. For example, synovial thickening with enhancement, with associated soft tissue edema, and bone marrow edema with enhancement suggest an underlying infective ideology, but it should be correlated with a joint aspiration. This is on a different patient who underwent ultrasound of the knee. Ultrasound has been shown to be sensitive in detection of synovitis, which can be used as a screening tool for any signs of inflammatory arthritis if there is already suspected one. In ultrasound, we can see some synovial thickening, hypervascularity, and complex joint effusion. For this patient, we can see the synovial thickening with hypervascularity and some complex joint effusion. This is also seen in the lateral aspect of the suprapatellar recess. Here again, we can see the thickened synovium right here with some increased hypervascularity and some complex joint effusion consistent with synovitis.

2nd Edition, CASE 30

2nd Edition

Knee

musculoskeletal radiology

synovitis diagnosis

MRI and ultrasound

quadriceps fat pad edema

Baker's cyst