Review Question - QID 216543

This patient who presents with knee pain after activity with mechanical symptoms (clicking, locking), an effusion (positive fluid displacement test), and a positive McMurray test (clicking or popping and pain when bringing the knee from flexion into extension while externally rotating the leg) most likely has a meniscal tear. The diagnosis of meniscal tears can be confirmed with an MRI.

Meniscal tears have a bimodal distribution, occurring in young patients through sports injuries and in older adults through degenerative processes. Medial tears are more common except when there is an acute anterior cruciate ligament tear, which is associated with lateral meniscal tears. Patients with meniscal injuries present with mechanical symptoms like locking or clicking of the knee, an effusion, and joint line tenderness. Provocative tests such as the McMurray test should be performed. The most sensitive diagnostic modality is an MRI. The initial treatment for degenerative meniscal tears (in older adults) is rest, non-steroidal anti-inflammatory drugs, and physical therapy. The initial treatment in younger adults is either partial meniscectomy or meniscal repair, depending on tear characteristics. Bracing or knee sleeves may be used for protection and compression.

Wang et al. review the accuracy of MRI studies for the diagnosis of meniscal tears. They state that the sensitivity and specificity of MRI for meniscal tears was 92.0% and 90.0% for medial meniscal tears and 80.0% and 95.0% for lateral meniscal tears, respectively. They recommend the use of MRI as the diagnostic imaging modality of choice for detecting medial and lateral meniscal tears.

Incorrect Answers:
Answer 1: Arthrocentesis is indicated in the work-up of a suspected septic joint. Septic joint presents with joint pain, effusion, and fever. Patients are typically unable to bear weight on the affected joint. However, mechanical signs are typically not present.

Answer 2: Computed tomography (CT) scan can be used in the work-up and surgical planning of tibial plateau fractures. Tibial plateau fractures present with severe knee pain, possible deformity, and edema. Plain radiographs are ordered first in the work-up of suspected fracture. CT scans visualize soft tissues poorly and are not used in the diagnosis of meniscal tears.

Answer 4: Plain radiograph of the knee can be ordered to rule out fractures or dislocations in trauma cases. There is no history of trauma in this patient to prompt suspicion for a fracture, and a knee radiograph would be normal in this patient with a meniscal tear.

Answer 5: Ultrasound is occasionally used in the office to evaluate knee pain, but has a lower sensitivity for meniscal tears compared to MRI. Diagnosis should be confirmed with MRI, not ultrasound.

Bullet Summary:
The diagnosis of a meniscal tear, which presents with mechanical signs (catching, popping, locking of the knee) and an effusion, can be confirmed with an MRI.