Accuracy of modified Akmese’s test for diagnosis of posterior horn medial meniscus root tear

INTRODUCTION

Posterior horn medial meniscus root tears (PHMMRTs) account for 10–21% of meniscal injuries and are often termed a “silent epidemic” due to their diagnostic challenges and high prevalence.^[1] If undetected or untreated, these tears can lead to accelerated cartilage damage, mimicking the effects of a total medial meniscectomy.^[2,3] Early diagnosis and treatment are therefore critical to prevent rapid joint degeneration.^[4]

Although magnetic resonance imaging (MRI) is highly sensitive for diagnosing PHMMRT lesions, its use in low-and middle-income countries (LMIC) is limited by its availability and high costs.^[5] Furthermore, its sensitivity and specificity vary depending on various factors.^[6] Although there are limited publications from LMIC about the sensitivity and specificity of MRI, we presume that, because of the lack of musculoskeletal radiologists in these countries, the sensitivity of MRI in detecting PHMMRT will be low. Hence, MRI in these regions cannot be used as a screening tool to detect PHMMRT. Akmese’s et al.^[7] described the Akmese’s sign to diagnose PHMMRT, which is based on the tenderness in the posteromedial joint line, which is less severe at higher knee flexion angles (120°) than extension or lower flexion angles (20°). We modified the original Akmese’s test by adding an additional step to confirm the change in tenderness severity. We hypothesized that the Modified Akmese’s test is sensitive and specific and can be used as a screening tool to determine the need for MRI.

Thus, this study aims to evaluate the diagnostic accuracy of the modified Akmese’s test and determine its usefulness as a screening tool to guide the need for MRI in patients with suspected PHMMRT. The secondary objective was to evaluate the diagnostic value of MRI in diagnosing PHMMRT.

MATERIALS AND METHODS

Study design

This was a single-center, prospective observational study conducted at the AKB center for arthroscopy, sports injuries, and regenerative medicine from January 2024 to January 2025. Ethical approval was obtained from the B&B Institutional Review Committee (approval number: IRC No B&BIRC-23-70), and all participants provided written informed consent. The Standards for Reporting Diagnostic Accuracy Studies guidelines were followed during the study (STARD-2015) [Figure 1].^[8]

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Figure 1:

Flow chart of methodology.

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Modified Akmese’s test

The classic Akmese’s test is performed in two steps, and the change in the intensity of tenderness is assessed only once. In this original description, palpation reveals that tenderness is significantly less when the knee is flexed to 120° than at 20°. However, this change in pain intensity relies on the patient’s subjective perception, which introduces a risk of misinterpretation.

To minimize this risk, we introduced an additional step to reconfirm the change in pain intensity. In our modification of the original “Akmese’s sign,” the test is performed in three steps, with the third step specifically added to verify the change in the intensity of tenderness [Figure 2].

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Figure 2:

(A) Key anatomical landmarks such as the joint line, medial collateral ligament (MCL), and the palpation point (posteromedial joint line) are shown. (B) (Step 1) The test begins by flexing the patient’s knee to about 20° and palpating the posteromedial joint line to assess tenderness levels. The tenderness is maximum at this point. (C) (Step 2) Maintaining thumb at the same spot, the knee is then flexed to 120°, and tenderness is evaluated. The intensity of tenderness would decrease significantly. (D) (Step 3) Finally, the knee is returned to the initial 20° of flexion, and the increase in tenderness is reconfirmed.

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• Step 1: The patient was positioned supine with the hip externally rotated and the knee flexed to 20° [Figure 2a]. The examiner palpated the posteromedial joint line using the thumb and assessed tenderness at this angle. The Visual Analog Scale (VAS) was recorded on a 10-point scale [Figure 2b].

• Step 2: Maintaining the thumb at the same location, the knee was gradually hyperflexed to 120°, and tenderness was re-evaluated in terms of VAS [Figure 2c]

• Step 3: Finally, the knee was again returned to 20° of flexion, keeping the thumb at the same location, and tenderness was again elicited to confirm the pain in extension [Figure 2d].

RESULTS

The final cohort comprised 82 patients who met the inclusion criteria and underwent complete evaluation. The mean age of participants was 45.46 ± 11.74 years, with a slight predominance of females (n = 47, 57.4%) compared to males (n = 35, 42.6%). The affected side was nearly evenly distributed, with 40 left knees (48.7%) and 42 right knees (51.3%). The average duration of symptoms before evaluation was 10.09 ± 7.07 months. These demographic and baseline characteristics are summarized in Table 1.

Table 2 summarizes the modified Akmese’s sign’s diagnostic performance compared to arthroscopy as the gold standard. There were 35 true positives, three false positives, two false negatives, and 42 true negatives. Similarly, the diagnostic performance of MRI compared to arthroscopy as the gold standard was 28 true positives, one false positive, nine false negatives, and 44 true negatives [Table 2].

The overall accuracy of the modified Akmese’s test was 93.9% (95% confidence interval [CI]: 86.3–97.7%). Sensitivity was 94.6% (95% CI: 81.8–99.3%), indicating a high ability to detect true PHMMRT cases. Specificity was 93.3% (95% CI: 81.7–98.6%), demonstrating strong performance in ruling out the condition in unaffected patients. The PPV was 92.1% (95% CI: 78.6–98.3%), and the NPV was 95.5% (95% CI: 84.5–99.4%). The positive LR+ was 14.19 (95% CI: 4.67–43.12), suggesting that a positive test result substantially increases the likelihood of PHMMRT. The negative LR was 0.06 (95% CI: 0.01–0.22), indicating that a negative result effectively decreases the probability of the condition.

ROC analysis yielded an AUC of 0.939 (95% CI: 0.888– 0.991; p < 0.001), confirming excellent discriminatory ability of the modified Akmese’s test for PHMMRT diagnosis. No significant differences were observed in test performance across subgroups based on age or sex (p > 0.05).

The overall accuracy of MRI was 87.8% (95% CI: 79.0–93.2%). Sensitivity was 75.7% (95% CI: 59.9–86.6%), indicating a moderate ability to detect true PHMMRT cases. Specificity was 97.8% (95% CI: 88.4–99.6%), demonstrating excellent performance in ruling out the condition in unaffected patients. The PPV was 96.6% (95% CI: 82.8–99.4%), and the NPV was 83.0% (95% CI: 70.8– 90.8%). The positive LR+ was 34.05 (95% CI: 28.22–41.09), suggesting that a positive MRI result substantially increases the likelihood of PHMMRT. The negative LR was 0.25 (95% CI: 0.14–0.44), indicating that a negative result moderately decreases the probability of the condition.

ROC analysis yielded an AUC of 0.867 (95% CI: 0.785– 0.950; p < 0.001), confirming good discriminatory ability of MRI for PHMMRT diagnosis. No significant differences were observed in test performance across subgroups based on age or sex (p > 0.05).

DISCUSSION

This study elaborated the performance metrics of the modified Akmese’s test for diagnosing PHMMRT, reporting a sensitivity of 94.5%, specificity of 93.3%, PPV of 92.1%, NPV of 95.4%, overall accuracy of 93.9%, and an area under the ROC curve AUC of 0.935. These values indicate a highly effective diagnostic tool, particularly for screening purposes, as the high sensitivity minimizes false negatives (missed cases), which is critical for a condition like PHMMRT that can lead to rapid knee osteoarthritis progression if undetected. The AUC of 0.935 reflects excellent discriminatory power, suggesting the test reliably distinguishes between those with and without the tear across various thresholds, outperforming many clinical tests where AUC values above 0.9 are considered outstanding. In addition, the balanced PPV and NPV imply that positive results are likely true positives in about 92% of cases, while negative results correctly rule out the condition in over 95%, providing strong clinical utility in resource-limited settings where confirmatory tests like MRI or arthroscopy may not be readily available. The diagnostic performance of the modified Akmese’s test was significantly better than the traditional meniscal tests, such as pain with full knee flexion (66.7% sensitive), joint line tenderness (61.9% sensitive), and the McMurray test (57.1% sensitive), demonstrating limited sensitivity for diagnosing PHMMRT.^[9-11]

Compared to the original Akmese’s et al.^[7] study, the modified test shows higher sensitivity (94.5% vs. 86.1%) but lower specificity (93.3% vs. 99.1%). This enhancement in sensitivity could stem from the added confirmation step in the modification, which likely reduces subjectivity in assessing tenderness changes at different knee flexion angles, thereby capturing more true cases that the original might miss due to patient variability in pain perception or examiner interpretation. However, the drop in specificity introduces a higher risk of false positives, potentially leading to overdiagnosis. The original study’s near-perfect specificity (99.1%) made it exceptionally strong for confirmatory testing, where minimizing false positives is prioritized. Still, its lower sensitivity risked missing up to 14% of cases. In contrast, the modified version’s metrics align better with screening criteria, where high sensitivity (>90%) is essential to identify at-risk patients early, even if specificity is moderately compromised.

Strengths of the modified test’s performance include its overall high accuracy (93.9%), which surpasses many physical examination maneuvers for meniscal pathologies, and the excellent AUC, which was not reported in the original study but would likely be lower given the Youden’s index of 0.85 (a proxy for balanced sensitivity and specificity).^[7] The NPV of 95.4% is particularly valuable, offering reassurance in ruling out PHMMRT and avoiding invasive procedures like arthroscopy in negative cases. However, weaknesses are evident in the comparison: The original study’s PPV (93.9%) and NPV (97.9%) were slightly higher, suggesting the modification may dilute predictive reliability due to increased false positives. Population differences, such as exclusion criteria (e.g., age 18–55 years and isolated medial lesions in both, but potentially varying comorbidities), and blinding protocols could also explain discrepancies.

Clinically, these values position the modified Akmese’s test as a superior screening tool over the original, especially in low-resource environments where MRI sensitivity for PHMMRT is variable (often 77–90%) and costly. Overall, the modification represents a meaningful advancement for early detection, but its lower specificity warrants cautious interpretation in high-prevalence settings to avoid diagnostic inflation.

In contrast, MRI’s lower sensitivity (75.6%) and moderate NPV (83.1%) limit its utility as a standalone screening tool, as it risks missing up to 24% of cases (higher false negatives, LR- = 0.25). However, its exceptional specificity and PPV, coupled with a high LR+ (34.05), position it strongly for confirmation: A positive MRI substantially increases the likelihood of true PHMMRT, justifying invasive procedures like arthroscopy. The accuracy (87.8%) and ROC AUC (0.867) reflect good overall performance, consistent with recent literature. Guimarães et al.,^[12] reported MRI sensitivity of 86–90% and specificity of 94–95% for medial posterior root tears, while Jhonatan et al.,^[6] in a meta-analysis cited that the sensitivity ranged between 90–96.7% and 96.7–100% specificity, placing this study’s values on the lower end for sensitivity but aligned for specificity. Tomsan et al.,^[13] noted that isolated MRI signs for root tears have high specificity (88–95%) but variable sensitivity (23–66%), reinforcing MRI’s confirmatory role when preceded by clinical screening. Thus, integrating the modified Akmese’s test for initial screening followed by MRI for positives optimizes diagnostic pathways, enhancing efficiency and patient outcomes in knee PHMMRT management.

The post hoc analysis suggests that the study was sufficiently powered (83%) to affirm the modified Akmese’s sign’s high sensitivity and specificity for screening purposes. In contrast, MRI’s excellent specificity was robustly demonstrated for confirmatory diagnosis. However, the low power for MRI’s sensitivity highlights potential under-detection risks and the need for larger samples in future validations. This also emphasized the role of the modified Akmese’s test as a screening tool and MRI as a confirmatory tool before suggesting invasive surgery.

CONCLUSION

The modified Akmese’s test is a highly accurate, sensitive, and specific clinical tool for diagnosing PHMMRTs. It has an overall accuracy of 93.9%, sensitivity of 94.5%, specificity of 93.3%, and an AUC of 0.939. By incorporating an additional confirmation step to assess tenderness variations at different knee flexion angles, the modification enhances the original Akmese’s sign’s utility, making it particularly effective for screening purposes.