Summary

The perception of a "pop" during a knee injury is a moderately predictive clinical indicator of a medial meniscal root tear and should be routinely inquired about while taking patient history.

Abstract

Purpose

Meniscal root tears change the biomechanics and kinematics of the knee leading to accelerated joint degeneration. Surgical intervention is indicated to repair these tears and restore biomechanics leading to better clinical and radiological outcomes. Accurate clinical diagnostic criteria for the presence of a meniscal root tear (MMRT) are not well established. This study aimed to evaluate the accuracy, sensitivity, specificity, and predictive values of hearing or feeling a “pop” for identifying isolated meniscal root tears.

Methods

This was a retrospective analysis of medical records of consecutive patients who underwent meniscal repair for isolated meniscal tears at our institution between January 2017 and July 2024. Exclusion criteria were previous ipsilateral knee surgery, fracture, or tumor, concomitant ligament injuries and presence of loose bodies during arthroscopy. Age, sex, and body mass index (BMI), report of a “pop” and type of tear as visualized during knee arthroscopy were extracted.
Accuracy, sensitivity, specificity, positive predictive value (ppv) and negative predictive value (npv) of perceiving a pop for a posterior root tear of the medial meniscus were calculated. Logistic regression analysis was performed to assess the impact of “pop” sensation on type of tear (MMRT, isolated root tear, and combined root tears) when adjusted for age, sex, and BMI. Cohort characteristics were reported using frequencies and mean±sd. When stratified by sex, differences were tested for significance between male and female subsets using chi-squared tests and t-tests. All analysis was done in python 3.10.0 with statsmodel 0.14.2 and scipy.stats 1.12.0.

Results

This analysis included 719 who underwent an isolated meniscus repair. 270 of these patients reported hearing or feeling a pop at the time of injury. 273 patients had medial meniscal root tears. The positive predictive value of having an isolated medial meniscus root tear after a perceived pop at injury was 44%, the negative predictive value was 73.1%, the sensitivity was 49.6%, the specificity was 68.5% and the diagnostic accuracy was 62.2%. There was a significant difference in the positive predictive value of a "pop" to indicate isolated MMRT in females (59%) vs males (29%) (p<0.001). Adjusted for age, BMI, and sex, the perception of a "pop" was significantly associated with isolated MMRTs, any isolated root tear, and combined root tears compared to other types of tears at a 2.7x, 2.3x and 2.3x greater risk respectively. Age, female sex and report of a “pop” were significantly associated with the presence of a root tear, while BMI was not.

Conclusion

This study found that the perception of a "pop" during a knee injury is a moderately predictive clinical indicator of a medial meniscal root tear in women and should be routinely inquired about while taking patient history.