1. MedPix Medical Image Database COW - Case of the Week Case Contributor: MS-4 USU Teaching File Affiliation: Uniformed Services University

2. MedPix No: 4310 - History Pt Demographics: Age = 24 y.o. Gender = Man This 24 year old active duty male complained of 8 weeks of medial left knee pain stemming from injury sustained while playing soccer. The patient reported a minimal effusion first noticed several days after initial injury. Downloaded by (-1)

3. MedPix No: 4310 - EXAM & LABS + tenderness to palpation medial joint line left knee, no effusions/ecchymoses, no joint laxity b/l, increased pain with Mcmurray*s manuever on left knee

4. MRI Knee hyperintense complex linear signal in posterior horn of left medial meniscus seen in images Downloaded by (-1)

5. MRI Knee hyperintense complex linear signal in posterior horn of left medial meniscus (arrow). Downloaded by (-1)

6. MRI Knee hyperintense linear signal in posterior horn left medial meniscus Downloaded by (-1)

7. MRI Knee hyperintense linear signal in posterior horn left medial meniscus Downloaded by (-1)

8. MRI Knee Hyperintense complex linear signal in posterior horn of left medial meniscus seen in images. Downloaded by (-1)

9. MRI Knee Hyperintense complex linear signal in posterior horn of left medial meniscus seen in images. Downloaded by (-1)

10. FINDINGS #1-hyperintense complex linear signal in posterior horn of left medial meniscus seen in images 16 - 20 of 44 (sagittal), appears to clearly communicate with articular surface in image 18 #2-hyperintense linear signal in posterior horn left medial meniscus (corresponding to #1) seen in image 5 of 20 (coronal)

11. DIFFERENTIAL DIAGNOSIS What is your Differential Diagnosis?

12. Diagnosis: Left medial meniscal posterior horn tear, grade 3 Dx Confirmed by:

13. DISCUSSION Meniscal injuries are the most common of all knee injuries, the medial meniscus being injured 10 times more frequently than the lateral due to the more firm attachment of the medial meniscus to the tibial plateau. Meniscal injuries commonly occur when the normal rotation of the tibia is forcibly prevented during flexion or extension; therefore the history usually involves a twisting injury, often medially with the knee in the full weight-bearing position or with a valgus stress while the knee is flexed. The patient*s history of an effusion occurring several days out from the initial injury was consistent with an isolated injury of the meniscus as meniscal injuries that occur with ligamentous injuries classically cause a large effusion (often hemorrhagic) acutely within minutes of the initial injury. The patient*s pain was intensified with the Mcmurray*s maneuver. Although this does not constitute a positive Mcmurray sign, which would be a palpable or audible click of upon performing the maneuver, the reproduction or intensification of the patient*s reported pain with this maneuver is nonetheless consistent with a meniscal tear. The injury in this case is classified as a Class 3 meniscal injury in the scheme originally proposed by Crues (1986) because it communicates with at least one articular surface on MRI. Class 3 injuries are usually symptomatic (pain, locking) and evident grossly upon visual inspection at either surgery or autopsy. In this scheme, Class 1 injuries are those that appear as globular (non-linear) signal abnormalities and do not communicate with an articular surface on MRI; these are frequently asymptomatic. Class 2 injuries are those that appear as linear signal abnormalities and do not communicate with articular surfaces on MRI; these are also frequently asymptomatic.