Figure. Coronal MRI shows a posterior horn medial meniscal root tear with mild extrusion.
A 34-year-old woman presents with right knee pain after an injury that occurred 2 weeks ago. She was pushing a wheel barrel when she planted her right foot and twisted to turn. She reports having immediate sharp knee pain and difficulty walking after the injury. On physical examination, she has mild effusion and sharp pain to palpation over the posterior medial joint line. Magnetic resonance imaging (MRI) scan shows a posterior horn medial meniscal root tear with mild extrusion (Figure, arrow). The articular cartilage remains intact.
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Meniscus tears are one of the most common injuries seen in orthopedic practice. The most common presentations of a meniscus tear include sharp knee pain with twisting or squatting, knee swelling, and pain to palpation over the affected joint line. Meniscus tears can occur in many different orientations including radial, vertical, bucket handle, horizontal, complex, and root tears. Root tears can be the most difficult to diagnose and may not be as obvious on MRI as other types of tears.1-3
The medial and lateral meniscus roots anchor the anterior and posterior meniscal horns to the tibia. A tear of the meniscal root (within 1 cm of the meniscus root attachment) decreases the shock absorption capabilities of the meniscus leading to increased contact pressure on articular cartilage.2 Meniscal root tears can occur in active adults from a traumatic injury or, more commonly (70%), a degenerative tear from chronic stress to the knee.2 Degenerative tears most commonly occur at the posterior root of the medial meniscus .1,2
The diagnostic study of choice for identifying meniscal root tears is MRI, although identifying these tears can be difficult. One study found that only 33% of root tears were identified on MRI despite being read by fellowship-trained musculoskeletal radiologists.3 The diagnosis is made with careful physical examination and patient history in conjunction with MRI findings.
Treatment involves surgical repair of the meniscal root to its native attachment site to prevent increased stress on the articular cartilage and decrease the rate of progressive arthritis.1,2 Patients with existing arthritis at the time of injury are better candidates for meniscectomy.
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Krych AJ, Hevesi M, Leland DP, Stuart MJ. Meniscal root injuries. J Am Acad Orthop Surg. 2020;28(12):491-499. doi:10.5435/JAAOS-D-19-00102
2. Pache S, Aman ZS, Kennedy M, et al. Meniscal root tears: current concepts review. Arch Bone Jt Surg. 2018;6(4):250-259.
3. Krych AJ, Wu IT, Desai VS, et al. High rate of missed lateral meniscus posterior root tears on preoperative magnetic resonance imaging. Ortho J Sports Med. 2018;6(4): 2325967118765722. doi:10.1177/2325967118765722