The Trapped Medial Meniscus Tear
An Examination Maneuver Helps Predict Arthroscopic Findings
Thomas A. Herschmiller, MBBS, Joh A. Anderson, MD, MSc, William E. Garrett, MD, PhD, and Dean C. Taylor, MD
Investigation performed at Duke University Medical Center Durham, North Carolina, USA
JACO Editorial Reviewer: Clark Labrum DC, DABCO
Journal of the Academy of Chiropractic Orthopedists
December 2016, Volume 13, Issue 2
The original article copyright belongs to the original publisher. This review is available from: http://www.dcorthoacademy.com ©
2016 Labrum and the Academy of Chiropractic Orthopedists. This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Numerous clinical examination maneuvers have been developed to identify meniscus tears of the knee. While meniscus injuries vary significantly in type and severity, no maneuvers have been developed that help to distinguish particular tear characteristics.
Purpose: This nonconsecutive case series highlights a distinctive clinical finding that correlates with inferiorly displaced flap tears of the medial meniscus that become trapped in the medial gutter of the knee, as identified through magnetic resonance imaging (MRI) and arthroscopy.
Study Design: Cohort study (diagnosis); Level of evidence, 3.
Methods: Eight patients with trapped medial meniscus tears were identified from a single surgeon’s academic orthopaedic sports medicine practice between January 2009 and January 2012. Each patient underwent clinical evaluation, MRI, and arthroscopic treatment for meniscus injury. Clinical notes, MRI images, radiology reports, and operative findings were reviewed and compared in a descriptive fashion.
Results: Each patient displayed a positive clinical examination finding of medial knee pain inferior to the joint line with flexion and the application of valgus stress in the setting of a torn medial meniscus and intact medial collateral ligament (MCL). Preoperative MRI revealed a distinctive flap tear of the medial meniscus flipped inferiorly to lay trapped between the tibia and deep fibers of the MCL. On arthroscopy, flap tears were found displaced inferiorly and trapped in the medial gutter in 6 of the 8 patients. Displaced meniscal fragments in the remaining 2 patients were found within the medial compartment.
Conclusions: Inferiorly displaced flap tears of the meniscus that have been displaced to the medial gutter can be localized through a careful examination technique.
Clinical Relevance: Early identification of this injury pattern may help reduce the likelihood that the trapped fragment will be missed during arthroscopy.
JACO Editorial Summary:
- Knee arthroscopy for a meniscus tear is one of the most commonly performed surgical procedures in the United States, with medial tears reported more commonly than lateral tears.
- Horizontal tears can produce fragments that become inverted and subsequently “trapped” between the medial aspect of the tibial plateau and the deep fibers of the medial collateral ligament (MCL) this particular type of medial meniscal tear may be more difficult to recognize during arthroscopy and if missed, results in ongoing knee pain postsurgery.
- The aim of this case series was to highlight that the finding of medial-sided pain with knee flexion and the application of a valgus stress, in the setting of an intact MCL, may indicate an inferiorly displaced flap tear of the medial meniscus.
- This maneuver was performed with the patient supine while the knee was flexed between 30 and 120 degrees by applying a valgus stress to the lateral aspect of the knee with the examiner’s free hand. In a positive test, the patient would experience a new or significant increase in pain directly adjacent and inferior to the joint line on the medial side of the tibia.
- Weaknesses of the study include the lack of prospective design and control group, the small sample size, and the fact that the examiner was not blinded to MRI findings.
As MRI accuracy improves, so does the risk of overreliance on this technology. One research study found that sole reliance on MRI without application of clinical judgment would have led to inappropriate treatment in 35% of knees studied. Other studies suggest experienced examiners are superior to MRI in identifying surgically treatable meniscal lesions. As fiscal constraints placed on medical management increase, MRI may be reserved for situations in which an experienced clinician requires further information before arriving at a diagnosis.
The clinical diagnosis of meniscal tears has been found to be more accurate when combinations of tests are use. Traditional maneuvers such as the McMurray test and the Apley compression test have low diagnostic accuracy when performed in isolation. However, by combining joint line tenderness and the McMurray test, researchers were able to lift sensitivity and specificity to over 90% for detection of a medial meniscus tear, and sensitivity to 75% and specificity to 99% for a lateral tear.
One proposal in 2006 included a history of mechanical symptoms combined with 4 examination maneuvers, however, a consensus does not exist regarding a composite evaluation for meniscal injury.
When the patient reported a positive history and experienced pain with hyperextension, maximum flexion, pain or click with the McMurray test, and joint line tenderness to palpation, there was a 92.3% positive predictive value of finding a meniscal tear.
Testing for medial-sided knee pain with flexion and application of valgus stress should be considered in patients for whom there is a concern of medial meniscal injury to avoid missing trapped inferiorly displaced flap tears on arthroscopy.