This 16-year-old female presents with lateral knee pain following a motor vehicle accident. No internal derangement, no meniscal tear. No bone bruising. What other features can be associated with lateral knee pain? What is indicated by the arrows on the images?
Strict attention to the lateral mensicus (LM) demonstrates normal superior meniscal fascicle attachment as the popliteus tendon enters the joint space (image 5, blue arrow); however, the inferior fascicle attachment is attenuated, frayed or torn (image 3, yellow arrow). Associated vertical striated edema (pink arrow, image 5) is posterior to the popliteofibular ligament and the arcuate ligament is swollen or sprained (red arrow, image 5). No myotendinous strain of the origin lateral gastrocnemius or popliteus tendon.
Take note of subtle anatomy in the setting of trauma, for instance, the popliteal fibular ligament (image 4, orange arrows). The yellow arrow in image 3 also points to a remnant stump of the inferior meniscocapsular fascicle to the LM, which is torn and likely contributes to pain. The teal arrow in image 2 points to a scalloped contour irregularity of the inferior patellar articular cartilage within the joint involving the lateral facet near the apex, class 2-3 chondromalacia.
IN ANSWER TO THE FIRST QUESTION, the green arrows on image 1 point to diffuse interstitial edema as a sequela of fluid extravasation toward the midline from posterolateral capsular injury. For more case review, check out MRI Online.
Dr. Stephen Pomeranz
Dr. Nick Trane