Preoperative Moderate Pivot-Shift Phenomenon: A Risk Factor for Ramp Lesions in Patients Undergoing Anterior Cruciate Ligament Reconstruction?

Abstract

Background:

While various risk factors for ramp lesions have been reported, few studies have used multivariate and categorical analyses to quantify their specific impact.

Hypothesis:

Multivariate and categorical analyses would reveal a smaller pivot-shift phenomenon, along with previously reported factors, as independent factors for ramp lesions.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

The records of consecutive patients who underwent primary anterior cruciate ligament reconstruction between January 2017 and August 2023 were retrospectively reviewed. Patients with past ligamentous injuries in the affected knee or accompanying grade 2 or 3 ligament injuries were excluded. Logistic regression analysis was performed to identify preoperative factors associated with ramp lesions by comparing groups with and without ramp lesions. The factors extracted from the multivariate analysis were also categorically analyzed.

Results:

A total of 262 patients were included in this study. Ramp lesions were identified in 58 patients (22.1%). Multivariate logistic regression analysis revealed that the pivot-shift test grade (OR, 1.560; 95% CI, 1.210-2.020; P < .01), age (OR, 0.966; 95% CI, 0.939-0.995; P = .02), and male sex (OR, 2.170; 95% CI, 1.120-4.190; P = .02) were independently associated with the ramp lesions. The categorical analysis revealed that the odds ratios for ramp lesions were 2.8-fold higher for those with pivot grade ≥4 than for those with grade <4, 2.0-fold higher for those aged <20 years than those aged ≥20 years, and 2.0-fold higher for males than females.

Conclusion:

Even a moderate pivot shift is a preoperative risk factor for ramp lesions, alongside younger age and male sex. Paying attention to these factors may reduce the chances of overlooking these lesions.

Keywords

meniscus anterior cruciate ligament risk factors

A meniscal ramp lesion is defined as a tear or disruption of the peripheral meniscocapsular attachments of the posterior horn of the medial meniscus and presents as a superior meniscocapsular ligament tear, an inferior meniscotibial ligament tear, or both.^3,15,25 Ramp lesions are typically associated with anterior cruciate ligament (ACL)–deficient knees and have a reported occurrence in 9.3% to 30.9% of all ACL tears.^1,2,15,23,25 The precise effects of ramp lesions are not fully understood; however, there is evidence to suggest they have significant biomechanical implications.¹⁷ A recent biomechanical study showed that a pivot shift was not always eliminated with ACL reconstruction (ACLR) alone but was restored when ACLR was performed simultaneously with a ramp lesion repair.³ Another study revealed increased external rotation and anterior translation in an ACL-deficient knee with concomitant ramp lesions and that only the repair of both injuries achieved normal knee kinetics.²⁶

Ramp lesions can be diagnosed using magnetic resonance imaging (MRI), but MRI shows only moderate sensitivity (although excellent specificity) for this diagnosis.^2,4,13,15 Ramp lesions are sometimes referred to as “hidden lesions” because they cannot be reliably diagnosed using classic anterior arthroscopy. Indeed, 40% of ramp lesions can be missed arthroscopically using the standard anterior views. Therefore, routine arthroscopic assessment through a transcondylar view or a posteromedial portal is necessary to confirm the absence or presence, extension, and type of ramp lesion.^{2,15,21,23,25}

Understanding the factors associated with ramp lesions, in combination with preoperative MRI findings, can reduce intraoperative oversights associated with these lesions. To date, various risk factors for ramp lesions have been reported, but few studies have used multivariate analysis to determine which factors influence ramp lesions and to what extent. In addition, there is a lack of studies that have more rigorously evaluated the relationship between ramp lesions and the pivot-shift phenomenon, although some reports have suggested an association between anterolateral rotatory instability and ramp lesions.^3,9 This study aimed to identify key preoperative factors associated with ramp lesions in ACL-injured knees, particularly examining the relationship between ramp lesions and the pivot-shift phenomenon. This relationship was assessed using the modified International Knee Documentation Committee (IKDC) criteria⁵ (grade 0 = negative; grade 1 = subtle glide, but not negative; grade 2 = glide; grade 3 = between grades 2 and 4; grade 4 = clunk [moderate]; grade 5 = between grades 4 and 6; grade 6 = gross) for a more rigorous evaluation.^10-12,19,30 While a gross pivot shift is a known risk factor for ramp lesions, no study has yet examined whether a clunk (moderate) pivot shift is also predictive of these lesions. We hypothesized that multivariate and categorical analyses would reveal a moderate pivot-shift phenomenon, along with previously reported factors, as independent factors for ramp lesions.

Methods

Patients

The records of consecutive patients who underwent primary ACLR between January 2017 and August 2023 at Tokyo Medical and Dental University Hospital were retrospectively reviewed. Patients with past ligamentous injuries in the affected knee or concomitant grade 2 or 3 injuries of the posterior cruciate ligament, lateral collateral ligament, or medial collateral ligament were excluded. This study was approved by the Institutional Review Board of the Tokyo Medical and Dental University (research protocol identification No. M2000-2054-01).

Clinical Evaluations and Arthroscopic Evaluations

Anterior knee laxity was measured with an arthrometer (KT-1000; MEDmetric) at the manual maximum pull and was expressed as the difference between the injured and uninjured knees in 0.5-mm increments. Anterolateral rotatory instability was evaluated using the pivot-shift test. We performed the pivot-shift test, incorporating both the traditional pivot shift and the N test as a series of maneuvers, enabling a more detailed evaluation.^6,18 Specifically, with the patient under anesthesia lying supine on the operating table, the examined extremity is lifted from the table. The extended leg is passively internally rotated and flexed while a valgus force and axial load are applied. Then, the leg is extended from 90° of flexion to full extension while maintaining a valgus force and internal rotation moment. For this test, the modified IKDC criteria⁵ were used as the grading system to provide a more rigorous evaluation of the pivot-shift phenomenon.^10-12,19,30 Evaluation of the pivot-shift test using these criteria was performed by 2 orthopaedic surgeons (H.K. and N.O.). These modified criteria have been shown to have high interrater reliability, with an intraclass correlation coefficient of 0.97 (95% CI, 0.94-0.98).¹⁰

Patient demographic data, including age, sex, time to surgery, frequency of giving way, and continuing to play sport after the initial injury, were recorded preoperatively. All physical examination results were recorded preoperatively at the time of surgery under anesthesia.

Arthroscopic findings, including the status of the meniscus and articular cartilage, were recorded at the time of surgery. Arthroscopy was performed by multiple surgeons (H.K., T.N., Y.N., T.H., M.A., A.Y. and N.O.) but always with 1 surgeon with >20 years of experience in knee surgery. A standard arthroscopic inspection was performed via anterolateral and anteromedial portals. A ruptured ACL was confirmed arthroscopically, and meniscal injury was managed according to the injury status. A complete or partial inferior tear, including a tear of the meniscotibial ligament, was classified as an unstable ramp lesion and was repaired using either all-inside sutures or inside-out sutures.^22,27 Transcondylar viewing of the posterior horn of the medial meniscus was routinely performed to identify ramp lesions. If a ramp lesion was suspected preoperatively but not visualized on the transcondylar view, a posteromedial portal was created for better visualization of the posterior medial meniscus.

Statistical Analysis

All statistical analyses were performed using EZR Version 1.61 (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing).⁷

The group with and the group without ramp lesions were compared using the chi-square test for categorical variables and the Mann-Whitney U test for continuous variables without a normal distribution. First, a univariate logistic regression analysis was performed to identify the factors that influenced ramp lesions. The dependent variable was ramp lesions, while the independent variables were age, sex, time to surgery, frequency of giving way, continuing to play sport after the initial injury, pivot-shift grade, side-to-side KT-1000 measurements using the manual maximal test, and lateral meniscus (LM) lesion. A multivariate logistic regression analysis was then performed on any variable with a P value <.2. A categorical analysis of factors extracted from the multivariate analysis was also performed. P values <.05 were considered statistically significant. Variables were selected based on previous literature.^14,25 To determine the sample size for the logistic regression analysis, the number of explanatory variables in the predictive model was considered. The number of events per predictive variable was 11.6.²⁰ Because there was minimal missing data, we included all patients in the analysis, using the available data without imputation.

Results

Based on the eligibility criteria, 262 patients were included in this study (Figure 1).

Figure 1.

Patient flow diagram. ACLR, anterior cruciate ligament reconstruction.

The patients’ demographic and intraoperative data are shown in Table 1. Ramp lesions were identified in 58 patients (22.1%). The group with ramp lesions showed significantly higher pivot-shift grade and younger age than the group without ramp lesions.

Table 1

Patients’ Demographic and Intraoperative Data ^a

	All (n = 262)	With Ramp Lesions (n = 58)	Without Ramp Lesions (n = 204)	P Value
Demographic, preoperative, and intraoperative evaluation
Age, y	28.9 ± 12.0	25.6 ± 9.8	29.9 ± 12.4	.02
Male sex	141 (53.8)	38 (65.5)	103 (50.5)	.06
Anterior knee laxity SSD, mm	4.8 ± 4.0	5.0 ± 2.8	4.7 ± 4.4	.22
Pivot-shift test				<.01
Grade 0	15 (5.7)	2 (3.4)	13 (6.4)
Grade 1	13 (5.0)	1 (1.7)	12 (5.9)
Grade 2	83 (31.7)	10 (17.2)	73 (35.8)
Grade 3	35 (13.4)	8 (13.8)	27 (13.2)
Grade 4	95 (36.3)	27 (46.6)	68 (33.3)
Grade 5	16 (6.1)	8 (13.8)	8 (3.9)
Grade 6	5 (1.9)	2 (3.4)	3 (1.5)
LM lesion	179 (68.8)	41 (70.7)	138 (68.3)	.85
Time to surgery, mo	3.1 (0.4-338.5)	3.3 (0.6-338.5)	3.0 (0.4-336.1)	.42
Giving way ^b				.06
0	159 (61.2)	28 (49.1)	131 (64.5)
1	82 (31.5)	25 (43.9)	57 (28.1)
2	19 (7.3)	4 (7.0)	15 (7.4)
Continuing sports after ACL tear	84 (32.3)	23 (40.4)	61 (30.0)	.19

Continuous variables are shown as mean ± SD, nominal variables are shown as n (%), ordinal variables are shown as median (range), and the pivot-shift test and frequency of giving way are shown as n (%) for each grade and category. The number of patients with missing data are as follows: anterior knee laxity SSD (n = 15), LM lesion (n = 2), time to surgery (n = 1), giving way (n = 2), and continuing sports after ACL tear (n = 2). Bold P values indicate statistical significance (P < .05). ACL, anterior cruciate ligament; LM, lateral meniscus; SSD, side-to-side difference.

The frequency of giving way from injury to surgery was categorized as 0 (never), 1 (1-5 times), or 2 (≥6 times).

Univariate logistic regression analysis revealed significant differences in the pivot-shift grade, age, and sex between the 2 groups (Table 2). A subsequent multivariate logistic regression analysis was performed, including the frequency of giving way and continuing sports after ACL tear (P < .2), along with the 3 variables.

Table 2

Results of the Univariate Logistic Regression Analysis ^a

	OR	95% CI	P Value
Age	0.967	0.941-0.994	.02
Male sex	1.860	1.020-3.420	.04
Anterior knee laxity SSD	1.020	0.952-1.090	.63
Pivot-shift test grade	1.580	1.230-2.020	<.01
LM lesion	1.120	0.591-2.120	.73
Time to surgery	1.000	0.997-1.010	.38
Giving way	1.430	0.918-2.240	.11
Continuing sports after ACL tear	1.570	0.86-2.89	.14

Bold P values indicate statistical significance (P < .05). ACL, anterior cruciate ligament; LM, lateral meniscus; SSD, side-to-side difference.

Multivariate logistic regression analysis revealed that the pivot-shift grade (OR, 1.560; 95% CI, 1.210-2.020; P < .01), age (OR, 0.966; 95% CI, 0.939-0.995; P = .02), and male sex (OR, 2.170; 95% CI, 1.120-4.190; P = .02) were independently associated with the ramp lesions (Table 3).

Table 3

Results of the Multivariate Logistic Regression Analysis ^a

	OR	95% CI	P Value
Pivot-shift test grade	1.560	1.210-2.020	<.01
Age	0.966	0.939-0.995	.02
Male sex	2.170	1.120-4.190	.02
Giving way	1.530	0.874-2.670	.14
Continuing sports after ACL tear	0.916	0.428-1.960	.82

Bold P values indicate statistical significance (P < .05). ACL, anterior cruciate ligament.

Categorical analyses of these 3 variables resulted in classification of the pivot-shift grade into 2 categories (grade <4 vs grade ≥4), and the odds ratio was calculated for ramp lesions of grade ≥4 and for lesions of grade <4. Grade 4 is defined as corresponding to a moderate pivot-shift phenomenon (see above for details on the grading system). The risk of ramp lesions was 2.8-fold higher in patients with grade ≥4 than in with those grade <4 (Table 4). A similar analysis revealed a 2.0-fold higher risk of ramp lesions in patients <20 years of age than in patients aged ≥20 years. The risk of ramp lesions was also 2.0-fold higher in males than in females.

Table 4

Results of the Categorical Analysis ^a

	OR (95% CI)	P Value
Pivot-shift test
Grade <4 (n = 146)	1.000 (reference)
Grade ≥4 (n = 116)	2.790 (1.520-5.110)	<.01
Age
>20 y (n = 199)	1.000 (reference)
≤20 y (n = 63)	1.970 (1.040-3.730)	.04
Sex
Female (n = 121)	1.000 (reference)
Male (n = 141)	2.030 (1.080-3.820)	.03

Bold P values indicate statistical significance (P < .05).

Discussion

The most important finding of this study was that even a moderate pivot-shift phenomenon was significantly associated with ramp lesions, along with younger age and male sex. Categorical analyses revealed that the risk of ramp lesions was 2.8-fold higher for a pivot grade ≥4 than for a grade <4, 2.0-fold higher for patients <20 years than those ≥20 years, and 2.0-fold higher for males than females.

Various risk factors for ramp lesions have been reported previously. For example, a risk factor analysis performed by Sonnery-Cottet et al²⁵ identified 769 patients with ramp lesions out of 3214 patients with ACL injury using the SANTI Study Group database. They reported that male sex, patients aged <30 years, revision ACLR, chronic injuries, preoperative side-to-side laxity >6 mm, and concomitant LM tears were risk factors for ramp lesions. Similarly, Tashiro et al²⁸ reported significantly longer delays in the time to surgery and larger anterior knee laxity in their patients with ramp lesions than in their patients with an intact medial meniscus. Comparing these results with our present results, anterolateral rotational instability, which has been reported to be linked to ramp lesions in some studies, was not included as a variable in these other studies.

Conversely, Thaunat et al²⁹ classified ramp lesions based on the location of the rupture and reported a significant association between gross pivot shift and complete ramp lesions according to their multivariate logistic regression analysis. These results align with previous studies indicating that ramp lesions are associated with anterolateral rotational instability.^3,17,26 While a gross pivot shift has been associated with ramp lesions in prior reports, there has been no report indicating that a moderate pivot shift is a preoperative risk factor for ramp lesions.

Kim et al⁸ reported that radiological findings, including deep posterior lateral femoral condyle, varus alignment, and steep medial tibial slope, were factors associated with ramp lesions. They suggested that the mechanism causing ramp lesions could be the increased rotational pivot-shift injury that initially occurs due to the deep lateral femoral condyle. A subsequent injury then occurs due to excessive anterior sliding of the medial tibial plateau, leading to a steep medial tibial slope and varus alignment. The result is an increase in the total range of the rotational arc, which then imposes higher stress on the posterior horn of the medial meniscus and meniscocapsular junction during knee injury, thereby causing a ramp lesion. Their radiological findings support our finding that a greater pivot shift is the factor most associated with ramp lesions.

A previous study identified LM lesions as having a significant association with ramp lesions.²³ However, this association was not observed in the present study. One possible explanation for this discrepancy is that our study did not differentiate LM tears by type (shape and size), which could influence their contribution to ramp lesions.

Univariate analysis revealed that the frequency of giving way and continuing sports after ACL tear, while not significant in the subsequent multivariate analysis, met the inclusion criterion (P < .2). The significant association between younger age and male sex with ramp lesions in the multivariate analysis might reflect the higher likelihood of younger men continuing sports and experiencing recurrent giving-way episodes after injury.

Ramp lesions can be routinely assessed transcondylarly in addition to standard arthroscopic evaluation of the cartilage, meniscus, and ligaments. However, if a ramp lesion is suspected preoperatively based on physical examination or MRI findings but not visualized transcondylarly, a posteromedial portal can provide better visualization of the relevant portion of the medial meniscus. Such a systematic approach minimizes the risk of overlooking these lesions.

The best procedure for repairing ramp lesions remains controversial. Previous studies have demonstrated that ramp lesions are longitudinal tears with little instability in the medial meniscus blood circulation field and that they may heal spontaneously without repair or when treated with abrasion and trephination alone.^16,24 However, ramp lesions do not resolve spontaneously in all cases. Our study demonstrates an association between ramp lesions and moderate pivot shifts, a finding not previously established. This suggests that treating ramp lesions may be beneficial for a wider range of patients with anterolateral instability, potentially including those with moderate pivot shifts, to help reduce residual instability and improve outcomes. Further research is warranted to confirm this.

Limitations

This study has several limitations. First, it was a retrospective study, which may introduce selection bias and confounding bias. Second, revision cases and cases with multiple ligament injuries were excluded from this study. However, we believe that our objective of identifying risk factors for ramp lesions in the setting of primary ACLR has been achieved. Third, this retrospective study lacks interrater reliability data for the 7-point pivot-shift grading scale, which could potentially affect the precision of the assessment. However, previous studies using this scale have demonstrated high reliability, and the same examiners and methodology were used in this study, suggesting a comparable level of reliability is likely.¹⁰ Fourth, the diagnostic nature of the study means it does not directly provide recommendations regarding treatment. Finally, the progression of ramp lesions over time was not investigated. However, we believe that paying attention to the factors identified in this study will reduce the likelihood of overlooking ramp lesions, thereby contributing to its clinical significance.

Conclusion

Even a moderate pivot shift is a preoperative risk factor for ramp lesions, alongside younger age and male sex, in patients undergoing ACLR. Paying attention to these factors may reduce the chances of overlooking ramp lesions.

Footnotes

Acknowledgements

The authors thank Toshitaka Yoshii, MD, PhD, for continuous support and Miyoko Ojima and Masayo Tsukamoto for organizing the data.

Final revision submitted January 12, 2025; accepted February 17, 2025.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was obtained from Tokyo Medical and Dental University (M2000-2054-01).

ORCID iD

Takashi Hoshino

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