Medial Meniscal Extrusion Evaluated with Weight-Bearing Ultrasound in Correlation with MRI: Differences in Meniscal Morphologies and Patient Symptoms

Presentation format: Oral presentation.

Purpose or Learning Objective: To compare medial meniscal extrusion as seen on weight-bearing ultrasonography (US) compared with magnetic resonance imaging (MRI) with consideration of meniscal morphology and patient symptoms.

Methods or Background: This study was approved by the institutional review board with informed consent. Patients with routine knee MRI were evaluated prospectively with supine and weight-bearing US of the medial meniscus. Position of the outer boundary of the medial meniscus on US images was measured relative to the tibia by two fellowship-trained musculoskeletal radiologists. Correlation was made to the presence or absence of reported meniscal degeneration or tear on MRI, as well as patient symptoms (Knee Outcome Survey Activities of Daily Living Scale). Statistical significance was calculated via intraclass correlation coefficient (ICC) and analysis of variance.

Results or Findings: A total of 99 knees from 95 subjects (50 men, 45 women; mean age: 45 ± 15 years) were included. The mean medial meniscal extrusion for a normal meniscus on MRI (n = 36) with supine US was 0.8 mm (1.6 mm on weight-bearing US). In the 20.2% (20/99) knees with mucoid degeneration of the meniscus on MRI, the mean medial meniscal extrusion with US was 1.6 mm supine (2.3 mm weight bearing), and the 43.4% (43/99) of knees with meniscal tear on MRI was 1.6 mm supine with US (2.3 mm weight bearing). Interreader reliability showed ICC values between 0.853 and 0.940.

Patients with meniscal tears versus a normal meniscus had on average higher symptom scores regarding stiffness (3.7 versus 3), limping (3.7 versus 2.8), squatting (4.2 versus 3.3), and sitting with bent knees (3 versus 2.2), with p values of 0.003 to 0.049. Mucoid degeneration only showed higher scores for squatting (3.9) but not the other parameters. Symptoms such as pain, swelling, and so on, were not significant to differentiate between the three groups.

Conclusion: A normal medial meniscus shows less mobility between the supine and upright positions than a pathologic meniscus. Mucoid medial meniscal degeneration shows laxity or extrusion in the supine and weight-bearing positions with US, even in the absence of meniscal tear on MRI. Mucoid degeneration and meniscal tears show a similar amount of extrusion. However, tears are more symptomatic.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
03 June 2021