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Abstract

Background:

Previous studies of concomitant meniscal injury in athletes with anterior cruciate ligament (ACL) injury have examined age, sex, body mass index (BMI), injury mechanism, and time from injury to surgery as potential risk factors.

Purpose:

To identify additional risk factors for concomitant meniscal injury, including preinjury joint laxity and lower extremity alignment, in athletes with sport-related ACL injury.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

This study included 180 participants aged 13 to 26 years who underwent ACL reconstruction (ACLR) after a first-time ACL injury sustained during participation in sport. Contralateral lower extremity alignment and joint laxity were used as surrogate measures for the injured knee before trauma. Concomitant meniscal tear patterns were identified at the time of ACLR. Sex-specific analyses were conducted.

Results:

Concomitant meniscal injury was observed in 60.6% of the subjects. The prevalence of concomitant injury was higher in male than female participants (69.9% vs 54.2%; P = .035) due to a higher prevalence of lateral meniscal injuries (56.2% vs 38.3%; P = .018). Among male patients, there was a significant difference in the prevalence of concomitant lateral meniscal tear according to sport participation (≥9 vs <9 h/week: 67.4% vs 35.7%; P = .032). Among male patients, the likelihood of concomitant injury to both the lateral and medial menisci increased by 28.8% for each 1-mm decrease in navicular drop. Among female patients, the likelihood of concomitant injury to the lateral meniscus increased by 15% per degree increase in genu recurvatum and 14% per degree decrease in standing quadriceps angle, with similar effects on the likelihood of concurrent injury to both the lateral and medial menisci.

Conclusion:

Measures of lower extremity alignment and genu recurvatum previously identified as risk factors for ACL injury were also associated with concomitant meniscal injury in female patients while other risk factors, including BMI and joint laxity, were not. Increased time spent participating in sport and navicular drop were associated with concomitant meniscal injury in male patients.

Keywords

anterior cruciate ligament knee meniscus risk factors trauma

The high incidence of anterior cruciate ligament (ACL) injuries among young athletes has been well documented across a wide range of sports, with rates for female patients generally being twice those of male patients after adjustment for age, the type of sport in which an athlete participates, and their level of play.^9,43 Not only are ACL injuries immediately debilitating, but young, active people who sustain this trauma also have a high risk of developing posttraumatic osteoarthritis of the affected knee within 15 years of injury.^1,29,33,50 With limited treatment options in young patients compared with older patients with idiopathic osteoarthritis, this becomes a serious problem. The risk of posttraumatic osteoarthritis after ACL injury is further elevated when there is concomitant injury to the menisci,^27,33 and evidence indicates that at least half of young people who sustain an ACL injury will also have a concomitant meniscal injury.^2,26,36

Given that young athletes are at higher risk not only for ACL injury but also for concomitant meniscal injury and subsequent development of posttraumatic osteoarthritis, identification of those at highest risk for a combined ACL and meniscal injury is of particular importance. Extensive epidemiologic research has been conducted to evaluate the demographic, anatomic, biomechanical, and joint geometry risk factors that predispose young athletes to a first-time ACL injury. These include the athlete’s sex,^9,20,39 sport,⁹ level of play,⁹ body mass index (BMI),^47,49 family history of an ACL injury¹⁸; a number of neuromuscular, lower extremity alignment, and joint laxity measures^47,49; and different features of knee joint geometry.^4,7,10,44,51 All of these studies included persons with and without concomitant meniscal injuries, but difficulty in obtaining and verifying surgical evidence of meniscal injury precluded the examination of isolated ACL injury and combined ACL and meniscal injury as distinct outcomes. The risk factors associated with the likelihood that an uninjured person will sustain a combined ACL and meniscal injury are therefore unclear.

To gain insight into potential risk factors for a combined ACL and meniscal injury, a number of investigators have compared patients with isolated ACL injury with those with ACL and concomitant meniscal injury at the time of ACL reconstruction (ACLR).^# The patient populations, variables examined, and types of meniscal injury have differed between studies, but the results indicate age below 30 years, male sex, higher BMI, and increased posterior slope of the tibial plateau may be associated with an increased prevalence of concomitant medial meniscal tears in those who sustain ACL injury.^42,52 Five of the studies focused on young patients undergoing ACLR, and they examined a select number of potential risk factors: age, sex, BMI, injury mechanism (contact vs noncontact), and time from injury to surgery.^{2,13,26,34,36} Although the results of these studies varied, they indicated that older teenagers and those with a higher BMI may be more likely to have a concomitant meniscal tear at the time of ACLR. Although the differences between ACL injured patients with and without a concomitant meniscal tear can help identify patient characteristics associated with the prevalence of meniscal injury in patients undergoing ACLR, they do not indicate the effect of those characteristics on the risk that an uninjured person will sustain a combined ACL and meniscal injury unless their association with risk of ACL injury is known.

A recent investigation assessed risk factors for first-time, noncontact ACL injury by monitoring high school and college sports teams to prospectively identify ACL injuries.^8,49 Potential risk factors were measured on each injured subject, and comparable measurements were obtained from randomly selected controls on the same team who had not sustained an ACL injury on or before the date the injured subject sustained trauma. Several demographic characteristics (increased weight, family history of ACL injury), increased joint laxity (knee and generalized), and lower extremity alignment measures (genu recurvatum, standing quadriceps angle, and navicular drop) were found to be significantly associated with increased risk of sustaining an ACL injury, and some of these risk factors differed between men and women.^8,49 In an ongoing prospective study of risk factors for contralateral ACL (CACL) injury in subjects 13 to 26 years of age, we obtain the same measurements on young people who sustained a first-time ACL injury and also obtain surgical information to identify concomitant meniscal injuries. This provided the opportunity for the current study, which assessed preinjury risk factors in terms of the odds of concomitant meniscal injury among patients with ACL injuries and combine the results with the odds of ACL injury from previous research to investigate their potential impact on the overall risk of a person sustaining a first-time ACL injury with concomitant meniscal injury.

The objective of the current study was to expand on previous reports of concomitant meniscal injury by evaluating whether knee laxity, generalized joint laxity, lower extremity alignment, age, sex, BMI, injury mechanism, and time spent participating in sport before injury are associated with concomitant meniscal injury in younger patients with sport-related ACL injuries.

Methods

Institutional review board approval was received for the study protocol, and all participants provided written informed consent. Data for this study were obtained as part of a prospective study designed to determine whether the risk factors for an injury to the CACL are similar to those associated with a first-time ACL injury. Recruitment for the CACL study is ongoing, and the analysis for this cross-sectional investigation included the baseline data from the initial 180 study participants, who were enrolled between February 1, 2019, and April 30, 2022 (Figure 1). Patients were eligible for the study if they were active, between the ages of 13 and 26 years, had sustained a first-time ACL injury, had undergone an ACLR, and were planning to return to participation in preinjury activities and sports.

Figure 1.

CONSORT flowchart of patient inclusion. ACL, anterior cruciate ligament; ACLR, ACL reconstruction; CONSORT, Consolidated Standards of Reporting Trials; IKDC, International Knee Documentation Committee.

After ACL injury and before surgery, all patients were counseled about limiting their activities and specifically instructed to discontinue sport participation. Subjects visited our laboratory to provide information about the time from injury to surgery (confirmed through the electronic medical records), and individual characteristics (age, sex, injury mechanism, and time spent participating in sport before injury) as well as to undergo measurement of body size (height, weight, and BMI), lower extremity alignment (passive and active genu recurvatum, hamstring extensibility, standing quadriceps angle, navicular drop, tibiofemoral angle, pelvic angle, tibial torsion, hip anteversion, tibia length, and femur length), and joint laxity (anterior-posterior [AP] knee displacement and generalized joint laxity). Lower extremity alignment and joint laxity measurements were obtained from the uninjured contralateral knee and used as a surrogate for the injured knee before trauma. Measurements were acquired using a handheld goniometer and linear caliper and can be made in a time-efficient manner in the clinic and all settings in the field. The approach used to make the measurements has been described,^8,49 and their inter- and intratester reliability have been reported.⁴⁰ Briefly, the same investigator acquired the demographic data, measurements of body size, lower extremity alignment using hand held calipers and goniometers, AP knee laxity using a KT-1000 arthrometer, and generalized joint laxity with the Beighton test on all subjects.

The presence of meniscal injury was determined at the time of ACLR by the surgeon, who also determined the pattern (longitudinal-vertical, horizontal, radial, vertical flap, complex, root tear, root avulsion, ramp lesion, or other) and location (circumferential and radial zones) of injury. Circumferential zones 1, 2, and 3 were the peripheral, middle, and inner one-thirds of the meniscal body, respectively, and the radial location was classified as posterior, anterior, or midbody of the meniscus (again divided into thirds).

Statistical Analysis

Potential risk factors were evaluated for their effects on any concomitant meniscal injury (≥1 tear in the medial and/or lateral meniscus), lateral meniscal injury (alone or with medial meniscal injury), medial meniscal injury (alone or with lateral meniscal injury), and injury to both menisci. Chi-square tests were used to assess differences in the prevalence of concomitant meniscal injury between age-groups, types of sport activity, injury mechanisms, years of sport participation, hours per week of sport participation, and weeks from ACL injury to surgery. Variables related to body size, lower extremity alignment, and knee joint and generalized laxity were compared between patients with versus without concomitant meniscal injury using t tests.

Logistic regression was used to assess the association of body size, lower extremity alignment, and knee joint and generalized laxity variables with concomitant injury to the lateral, medial, or both menisci. Odds ratios (ORs) and 95% confidence intervals (CIs) corresponding to a 1-unit increase of the variable considered in the analysis were calculated. To control for the influence of any meniscal injuries that may have occurred after the ACL injury, all logistic regressions were repeated with the number of weeks between ACL injury and surgery (when documentation of concomitant meniscal injury occurred; ≤5, 5.1-10, and >10 weeks) as a covariate. P≤.05 was considered statistically significant.

Results

Characteristics of Study Patients

A total of 180 patients with ACL injury (73 male and 107 female patients) were included in the study. All patients had undergone ACLR between 1 and 28 weeks after the index injury (median, 7 weeks), with 90.6% having surgery within 15 weeks of the index injury. At the time of surgery, 109 (60.6%) of the subjects were documented as having sustained 1 or more concomitant meniscal injuries via arthroscopic examination. The distribution of participants by time between injury and surgery is shown in Supplemental Table S1, available online. We found no relationship between the time from ACL injury to surgery and the prevalence of either lateral or medial meniscal injury (see Supplemental Table S2, available online), although the prevalence of meniscal injury was highest (78.6%) in the 14 patients (7.8%) who had surgery within 3 weeks of their ACL injury. A total of 35 subjects (19.4%) had multiple meniscal injuries, for a total of 156 tears.

Characteristics of Patients With Concomitant Meniscal Injury

Of the 109 subjects with concomitant meniscal injury, 82 sustained an injury of the lateral meniscus (52 with only lateral injury and 30 with concurrent injury to the medial meniscus) while 57 had a medial meniscal injury (27 with only medial meniscal injury). Male patients had a significantly higher prevalence of concomitant meniscal injury compared with female patients (69.9% vs 54.2%, P = .035) due to a significantly higher prevalence of lateral meniscal injury (56.2% vs 38.3%, P = .018). Male and female patients did not differ significantly in the prevalence of concomitant medial meniscal injury (29.9% vs 34.3%, P = .53) or concurrent injury to both lateral and medial menisci (14.0% vs 20.6%, P = .25).

Clinical features of the 156 meniscal injuries according to patient sex are shown in Table 1. A majority of the medial meniscal injuries occurred in zone 1 (70.0 % and 62.5% for female and male patients, respectively), and most of the medial meniscal injuries were located in the posterior horn (97.0% and 88.0% for female and male patients, respectively). Similarly, a majority of the lateral meniscal injuries were located in the posterior horn (76.6% and 67.4% for female and male patients, respectively) and fewer occurred in zone 2 (13.6% and 4.4% for male and female patients, respectively) than zones 1 and 3. In the medial meniscus, longitudinal vertical tears were the most common pattern for female (60.6%) and male (36.0%) patients, while lateral meniscal tears most frequently demonstrated longitudinal or radial patterns (female patients; 37.5% and 31.3%, and male patients; 32.6% and 39.1%, respectively).

Table 1

Characteristics of Patients with Concomitant Meniscal Injury by Sex (N = 109 Patients, 156 Tears)^a

	Male Patients (n = 51)		Female Patients (n = 58)
	Medial Meniscal Tear (n = 27)	Lateral Meniscal Tear (n = 47)	Medial Meniscal Tear (n = 34)	Lateral Meniscal Tear (n = 48)
Circumferential zone
Zone 1	15 (62.5)	11 (23.9)	21 (70.0)	16 (36.4)
Zone 2	0 (0)	2 (4.4%)	2 (6.7)	6 (13.6)
Zone 3	4 (16.7)	18 (39.1)	4 (13.3)	16 (36.4)
>1 zone	5 (20.8)	15 (32.6)	3 (10.0)	6 (13.6)
Missing	3	1	4	4
Radial location
Posterior	22 (88.0)	31 (67.4)	32 (97.0)	36 (76.6)
Anterior	1 (4.0)	2 (4.4)	0 (0)	2 (4.3)
Midbody	0 (0)	11 (23.9)	0 (0)	7 (14.9)
>1 location	2 (8.0)	2 (4.4)	1 (3.0)	2 (4.3)
Missing	2	1	1	1
Pattern
Longitudinal-vertical	9 (36.0)	15 (32.6)	20 (60.6)	18 (37.5)
Horizontal	1 (4.0)	0 (0)	3 (9.1)	1 (2.1)
Radial	1 (4.0)	18 (39.1)	1 (3.0)	15 (31.3)
Vertical flap	2 (8.0)	4 (8.7)	2 (6.1)	5 (10.4)
Complex	3 (12)	4 (8.7)	0 (0)	5 (10.4)
Root tear	0 (0)	4 (8.7)	2 (6.1)	2 (4.2)
Root avulsion	0 (0)	0 (0)	0 (0)	1 (2.1)
Other	4 (16.0)	1 (2.2)	1 (3.0)	1 (2.1)
Ramp lesion	5 (20.0)	0 (0)	4 (12.1)	0 (0)
Missing	2	1	1	0

Data are presented as No. of tears (%).

For both male and female patients, the highest prevalence of concomitant meniscal injury of any kind (medial, lateral, or combined medial and lateral) was observed for those who participated in indoor sports that involved plant, cut, and/or jump movements (62.5% and 77.4% for female and male patients, respectively). A high prevalence of concomitant meniscal injury of any kind was also observed among male patients participating in snow sports (72.0%) but not among female patients (44.0%). However, none of the observed differences associated with age, type of sport, injury mechanism, or hours per week and years of sport participation were statistically significant for either male or female patients (Table 2). Likewise, the prevalences of lateral and medial meniscal injury were not significantly associated with age, type of sport, injury mechanism, or years of sport participation for either male or female patients (data not shown). However, in male patients, those who participated in sport for at least 9 hours per week were almost twice as likely to have a concomitant lateral meniscal tear compared with those who participated for less than 9 hours per week (67.4% vs 35.7%, respectively; P = .032). A similar relationship did not exist for the female patients (44.1% vs 30.6%, P = .18).

Table 2

Prevalence of Concomitant Meniscal injury Based on Patient Characteristics and Sex (n = 180)^a

	Male Patients (n = 73)				Female Patients (n = 107)
	No Meniscal Injury (n = 22)	Meniscal Injury (n = 51)	Prevalence, %	P	No Meniscal Injury (n = 49)	Meniscal Injury (n = 58)	Prevalence, %	P
Age, y				.65				.969
12-14	3	3	50.0		8	10	55.6
15-17	5	15	75.0		21	27	56.3
18-21	10	21	67.7		14	15	51.7
>22	4	12	75.0		6	6	50.0
Type of sport				.201				.194
Indoor plant, cut, jump	7	24	77.4		21	35	62.5
Outdoor plant, cut, jump	8	9	52.9		14	12	46.2
Snow sports	7	18	72.0		14	11	44.0
Years participated in sport				.098				.990
0-5	8	6	42.9		8	10	55.6
6-10	5	17	77.3		19	23	54.8
11-15	3	13	81.3		16	18	52.9
>16	6	12	66.7		6	6	50.0
Hours/week participated in sport				.437				.246
0-4	6	8	57.1		7	13	65.0
5-8	5	9	64.3		10	6	37.5
>9	11	32	74.4		30	38	55.9
Injury mechanism				.859				.282
Noncontact	20	47	70.1		42	45	51.7
Contact	2	4	66.7		7	13	65.0

Data are reported as No. of injuries unless otherwise indicated.

Results of Logistic Regression Analysis

None of the variables for body size, lower extremity alignment, or joint laxity differed significantly between patients with versus without any concomitant meniscal injury (medial, lateral, or combined), for either male or female patients (Table 3). Similarly, body size and joint laxity were not associated with the likelihood of injury to either the lateral meniscus or medial meniscus or to injuries in both medial and lateral menisci for either male or female patients (Table 4). However, among female patients, the likelihood of concomitant injury to the lateral meniscus and concurrent injuries to both medial and lateral menisci was significantly associated with several measures of lower extremity alignment (Table 4). For female patients, a decrease in passive genu recurvatum (indicating a less negative angle or decreased hyperextension) was associated with decreased odds of concomitant lateral meniscal injury (OR per degree decrease, 0.87; 95% CI, 0.77-0.97) and decreased odds of concurrent injuries to both medial and lateral menisci (OR per degree decrease, 0.78; 95% CI, 0.66-0.92). Hence, the corresponding increase in the odds of a concomitant lateral meniscal injury per degree of increase in passive genu recurvatum (increased hyperextension) was 14.9%. A similar relationship was observed among female patients for decreased active genu recurvatum: lateral meniscal injury (OR per degree decrease, 0.88; 95% CI, 0.78-0.99, corresponding to a 13.7% increase in the odds of a lateral meniscal injury for each degree of increase in hyperextension) and injuries to both the lateral and medial menisci (OR per degree decrease, 0.73; 95% CI, 0.60-0.88). In addition, for the female patients, an increase in the standing quadriceps angle (Q angle) was associated with a significant decrease in the odds of concomitant lateral meniscal injury (OR per degree increase, 0.87; 95% CI, 0.78-0.98), corresponding to a 14.4% increase in the odds of lateral meniscal injury for each degree decrease in standing quadriceps angle). Associations were also observed between Q angle and the odds of a female patient sustaining concomitant ACL injury and injury to both lateral and medial menisci (OR per degree increase, 0.84; 95% CI, 0.72-0.98, corresponding to a 19% increase in odds of combined medial and lateral meniscal injury for each degree decrease in standing quadriceps angle).

Table 3

Body Size, Lower Extremity Alignment, and Joint Laxity Variables in Patients With and Without Concomitant Meniscal Injury^a

	Male Patients (n = 73)			Female Patients (n = 107)
	No Meniscal Injury (n = 22)	Meniscal Injury (n = 51)	P	No Meniscal Injury (n = 49)	Meniscal Injury (n = 58)	P
Body size
Height, cm	177.5 ± 7.1	178.8 ± 7.4	0.53	165.9 ± 6.4	166.1 ± 5.6	.83
Weight, kg	80.3 ± 12.6	84.9 ± 15.3	0.22	66.3 ± 12.5	65.5 ± 9.9	.69
BMI, kg/m²	25.4 ± 3.6	26.5 ± 4.4	0.30	23.9 ± 3.7	23.7 ± 3.4	.67
Lower extremity alignment
Genu recurvatum: passive, deg	-7.1 ± 3.7	-6.7 ± 3.4	0.66	-6.6 ± 3.5	-7.4 ± 3.6	.24
Genu recurvatum: active, deg	-5.4 ± 3.5	-4.9 ± 3.3	0.58	-5.2 ± 3.2	-5.7 ± 3.4	.43
Hamstring extensibility, deg	21.2 ± 11.8	15.8 ± 10.9	0.053	14.8 ± 10.3	14.7 ± 8.2	.97
Standing quadriceps angle, deg	6.5 ± 3.5	7.5 ± 2.9	0.23	9.6 ± 3.4	8.8 ± 3.9	.27
Navicular drop, mm	10.4 ± 3.9	10.2 ± 4.4	0.91	9.6 ± 3.5	9.2 ± 2.9	.57
Tibiofemoral angle, deg	4.5 ± 2.1	5.5 ± 2.1	0.60	7.6 ± 2.2	7.0 ± 2.6	.78
Pelvic angle, deg	9.3 ± 3.9	11.2 ± 4.0	0.055	12.3 ± 3.2	12.7 ± 3.1	.54
Tibial torsion, deg	18.6 ± 2.8	19.1 ± 6.9	0.75	18.7 ± 4.4	18.2 ± 4.9	.58
Hip anteversion, deg	1.3 ± 4.9	2.7 ± 5.4	0.31	0.4 ± 5.8	0.6 ± 5.0	.90
Tibia length, cm	40.6 ± 2.6	41.2 ± 2.2	0.37	37.8 ± 2.5	38.0 ± 1.8	.58
Femur length, cm	44.3 ± 2.8	44.1 ± 2.4	0.76	41.1 ± 2.2	41.6 ± 2.3	.24
Knee joint and generalized laxity
AP displacement, mm	15.0 ± 4.3	14.72 ± 2.8	0.74	15.9 ± 2.6	16.1 ± 2.9	.63
Posterior stiffness, N/mm	24.7 ± 5.6	23.34 ± 5.1	0.30	23.5 ± 5.2	22.6 ± 4.1	.34
Anterior stiffness, N/mm	16.9 ± 5.6	16.61 ± 4.6	0.80	14.9 ± 4.4	15.1 ± 3.8	.82
Generalized joint laxity^b	1.7 ± 1.9	1.92 ± 1.7	0.67	2.5 ± 1.9	2.6 ± 1.7	0.70

Data are reported as No. of injuries unless otherwise indicated.

Total Modified Beighton score.

Table 4

Association of Body Size, Lower Extremity Alignment, and Joint Laxity Variables With Concomitant Meniscal Injury by Patient Sex^a

	Male Patients			Female Patients
	Lateral Meniscal Injury	Medial Meniscal Injury	Injury to Both Menisci	Lateral Meniscal Injury	Medial Meniscal Injury	Injury to Both Menisci
Body size
Height	1.11 (0.94-1.32)	0.97 (0.82-1.15)	1.05 (0.86-1.29)	1.06 (0.89-1.26)	1.00 (0.84-1.20)	1.08 (0.86-1.37)
Weight	1.00 (0.99-1.02)	1.01 (0.99-1.03)	1.01 (0.99-1.02)	1.00 (0.99-1.02)	0.99 (0.97-1.01)	1.00 (0.97-1.02)
BMI	0.99 (0.89-1.11)	1.10 (0.98-1.24)	1.04 (0.91-1.19)	1.01 (0.91-1.13)	0.91 (0.80-1.04)	0.93 (0.78-1.11)
Lower extremity alignment
Genu recurvatum passive	0.97 (0.85-1.12)	1.11 (0.95-1.28)	1.06 (0.89-1.25)	0.87 (0.77-0.97)	0.94 (0.84-1.05)	0.78 (0.66-0.92)
Genu recurvatum active	0.99 (0.86-1.14)	1.10 (0.95-1.29)	1.07 (0.90-1.27)	0.88 (0.78-0.99)	0.92 (0.81-1.04)	0.73 (0.60-0.88)
Hamstring extensibility	0.99 (0.95-1.04)	0.95 (0.91-1.00)	0.99 (0.93-1.04)	1.00 (0.95-1.04)	0.99 (0.95-1.04)	0.98 (0.92-1.05)
Standing quadriceps angle	1.03 (0.88-1.20)	1.10 (0.94-1.29)	1.04 (0.86-1.25)	0.87 (0.78-0.98)	0.98 (0.87-1.10)	0.84 (0.72-0.98)
Navicular drop	0.94 (0.84-1.05)	0.93 (0.82-1.06)	0.78 (0.64-0.95)	0.94 (0.83-1.07)	1.00 (0.88-1.14)	0.95 (0.80-1.13)
Tibiofemoral angle	1.18 (0.94-1.49)	1.00 (0.79-1.25)	0.94 (0.72-1.24)	1.00 (0.85-1.18)	0.85 (0.70-1.02)	0.78 (0.61-1.00)
Pelvic angle	1.04 (0.93-1.17)	1.06 (0.94-1.20)	0.98 (0.85-1.13)	1.01 (0.90-1.15)	1.00 (0.87-1.14)	0.94 (0.79-1.12)
Tibial torsion	1.01 (0.93-1.09)	1.07 (0.96-1.20)	1.10 (0.95-1.27)	0.93 (0.85-1.01)	1.03 (0.94-1.13)	0.95 (0.85-1.06)
Hip anteversion	1.02 (0.90-1.12)	1.09 (0.99-1.20)	1.09 (0.97-1.22)	1.02 (0.95-1.10)	1.02 (0.95-1.10)	1.07 (0.97-1.18)
Tibia length	1.11 (0.90-1.36)	0.99 (0.80-1.22)	1.01 (0.79-1.30)	1.06 (0.88-1.28)	1.07 (0.88-1.30)	1.13 (0.88-1.46)
Femur length	1.06 (0.88-1.28)	0.91 (0.75-1.11)	1.00 (0.80-1.27)	1.09 (0.92-1.31)	1.12 (0.93-1.36)	1.17 (0.91-1.52)
Knee joint and generalized laxity
AP displacement	0.96 (0.83-1.11)	0.99 (0.85-1.15)	0.95 (0.79-1.14)	1.07 (0.92-1.23)	1.11 (0.95-1.29)	1.25 (1.02-1.53)
Posterior stiffness	0.97 (0.89-1.06)	1.00 (0.91-1.10)	1.02 (0.92-1.14)	0.97 (0.89-1.06)	0.99 (0.90-1.08)	1.00 (0.89-1.13)
Anterior stiffness	1.02 (0.93-1.13)	0.90 (0.80-1.00)	0.90 (0.79-1.03)	1.05 (0.95-1.16)	0.99 (0.89-1.10)	1.05 (0.92-1.19)
Generalized joint laxity^b	0.98 (0.75-1.27)	0.99 (0.75-1.30)	0.86 (0.60-1.24)	1.04 (0.83-1.29)	1.07 (0.85-1.34)	1.10 (0.82-1.47)

Comparison group: patients with ACL injury without concomitant meniscal injury. Data are presented as OR (95% CI) corresponding to a 1-unit increase of the variable considered in the analysis. Bolded text indicates statistical significance (P ≤ .05). AP, anterior-posterior; BMI, body mass index; CI, confidence interval; OR, odds ratio.

Total modified Beighton score.

Among male patients, there were no significant associations between lower extremity alignment of the knee and injury to either the lateral or medical meniscus. However, an increase in navicular drop was associated with decreased odds of sustaining concomitant injuries to the both lateral and medial menisci (OR per 1 mm increase, 0.78; 95% CI, 0.64-0.95), corresponding to a 28.8% increase in the likelihood of concomitant injury to both menisci for each 1 mm decrease in navicular drop). Adjustment for time between ACL injury and surgery had a negligible effect on OR (Supplemental Table S3, available separately).

Discussion

The majority (60.6%) of the young active participants in our study of first-time, acute ACL trauma had at least 1 concomitant meniscal injury identified via arthroscopic visualization. This finding is comparable with the 63.0% prevalence in a similar cohort of subjects reported by Kolin et al.²⁶ We found that there were more injuries to the lateral than the medial meniscus. In addition, we found that male patients were 36% (rate ratio, 1.36) more likely to sustain a concomitant meniscal injury and were 47% more likely to have a concomitant injury of their lateral meniscus than female patients.

These results are in contrast to a study of pediatric patients (age ≤18 years) by Perkins et al³⁶ that found no difference in the rates of meniscal injury between male and female patients, but are nearly the same as the 46% higher prevalence of lateral meniscal injury in male patients reported by Kolin et al.²⁶ Importantly, the overall risk of an ACL injury with a concomitant meniscal injury is higher for female patients because their incidence of ACL injury is nearly twice that of male patients after controlling for sport, age, and level of play.⁹ In addition, although body size is associated with the risk of sustaining an ACL injury, we did not find it to be associated with the prevalence of concomitant meniscal injury in those who sustain an ACL injury. Our results differ from those of Perkins et al,³⁶ who found BMI to be associated with increases in medial and lateral meniscal injuries. The difference in the findings between our investigation and that of Perkins et al³⁶ may be attributed to the fact that their analysis was based on combined data from male and female patients, while our investigation considered male and female patients separately.

Previous research has found that both increased AP knee laxity of the tibiofemoral joint and increased generalized joint laxity are associated with increased risk of sustaining ACL injury in male and female patients.^8,47,49 The current study revealed that the prevalence of concomitant injury to the meniscus among patients with ACL injury was not associated with these measures of joint laxity in either male or female patients. This observation may be explained by the fact that the ACL is the primary restraint to anterior translation and anterior-directed loading of the tibiofemoral joint (eg, a portion of the coupled motions between the tibia relative to the femur associated with ACL trauma) and that the posterior horns of the menisci contribute little to limiting anterior-directed displacement/loading of the tibia relative to the femur in the ACL-deficient knee.¹² There appears to be consensus in the literature that increased preinjury AP knee laxity is an established risk factor for ACL injury, and the current investigation suggests that increased preinjury laxity of the knee is not associated with additional risk of injury to the menisci.

We found that male athletes who participated in sport for 9 or more hours per week were almost twice as likely to sustain an ACL injury and concomitant tear to their lateral meniscus compared with those who participated fewer than 9 hours per week (67.4 % vs 35.7 %, P = .032). Previous studies reported by Kim et al,²² Chen et al,¹⁴ and Lipps et al²⁸ showed that accumulation of ACL fatigue damage, produced by repetitive submaximal loading cycles over time, reduces the structural properties and weakens the ACL. Future research needs to be done to determine whether an extended period spent participating in activities that strain the menisci also accumulates fatigue damage by repetitive submaximal loading over time, which may outpace the biologic capacity of the menisci to repair the fatigue damage, thereby reducing the biomechanical properties and predisposing them to an elevated risk of failure during high demand activities. If such a mechanism exists, the type of sport and a person’s level of competition could be linked to the time they spend participating and subsequently the risk of sustaining ACL and concomitant meniscal injury. We should point out, however, that, although the hours of sport participation was similar for male and female participants, there was no evidence of a relationship with concomitant meniscal injury for the female patients. This suggests that the relationship between combined ACL and meniscal injury and duration of time spent participating in sport may be dependent on patient sex.

Associations between select measures of lower extremity alignment and the likelihood of sustaining concomitant injury to the menisci differed between ACL-injured male and female athletes, suggesting that the mechanism of load and torque transmission across the knee that produces severe trauma involving both the ACL and meniscus differed between the sexes. For the ACL-injured male patients, the likelihood of concomitant injury involving both the medial and lateral menisci increased by 28.8% for each 1-mm decrease in navicular drop (ie, a more rigid arch of the midfoot). The results for injury to either the medial (OR, 0.93) or lateral (OR, 0.94) meniscus almost reached significance, further supporting an inverse association between navicular drop and risk of concomitant meniscal injury. This is in contrast to previous research in a similar cohort of subjects that found the likelihood of sustaining ACL injury increased by 12% for each 1 mm increase in navicular drop.⁸ Previous gait research by Eslami et al¹⁵ on a cohort of men with demographic characteristics similar to our subjects revealed that, during the stance phase of running, decreased navicular drop was associated with increased internal rotation of the tibia, whereas increased navicular drop was associated with increased peak adduction moment about the knee. Considered in relation to our results, this suggests that the magnitude of navicular drop, either increased or decreased, may have a direct effect on both the magnitude and direction of the impulsive intersegmental loads (ie, compression, internal torque, and adduction torque) that are transmitted across the tibiofemoral joint during a traumatic event. This, in turn, may have an effect on which structures of the knee are injured. For example, males with a decrease of navicular drop and increased coupled internal tibial rotation may be more likely to experience combined ACL and meniscal injury, while those with increased navicular drop and the increased coupled adduction torque that acts on the knee may be more likely to sustain an ACL injury in isolation. If these mechanisms exist, it will be important to also consider the effect of the articular surface geometry such as slope of the tibial plateau and height and location of the tibial spines as these structures also influence how loads and torques are transmitted across the knee, ACL, and menisci. It is important for us to point out that the work by Eslami et al¹⁵ focused on men, and it is unclear whether their findings are applicable to women; therefore, future research in this area is needed to clarify differences between male and female athletes.

Analysis of female athletes with ACL injuries revealed that increased genu recurvatum (measured both passively and actively) was associated with an increase in the likelihood of concomitant injury to the lateral meniscus, as well as injury involving both the lateral and medial menisci. Previous research on athletes of similar age and demographic characteristics revealed nearly the same relationships with the likelihood of ACL injury.^8,49 Taken together, current and previous studies suggest that female athletes with increased genu recurvatum of the knee have a particularly high risk of sustaining trauma that involves combined injury to both the ACL and meniscus. Owens³⁵ suggested that increased genu recurvatum may be an indirect measure of the quality, structure, and composition of the soft tissues around the knee, such as the ACL and menisci, and ultimately their biomechanical failure characteristics.

In addition to genu recurvatum, female patients with a decreased standing quadriceps angle were found to be associated with increased likelihood of ACL and lateral meniscal injury. This finding is important to consider in the context of previous work reporting that a decrease in standing quadriceps angle increases the medial tibiofemoral contact pressure by increasing tibiofemoral varus orientation.³² An increase in varus changes how the magnitude and direction of the intersegmental loads and torques transmitted across the medial and lateral compartments of the tibiofemoral joint and this, in turn, may have a direct effect on how the medial and lateral menisci are loaded during injury and subsequently the pattern and location of the injury. For example, an increase in varus torque would produce an increase and decrease of the compressive forces acting across the medial and lateral compartments, respectively. In turn, the increased compressive load acting across the congruent medial compartment of the tibiofemoral joint may act to provide added resistance to the intersegmental loads that challenge the ACL while a proportional decrease of the compressive loads may reduce the stability provided by articular congruence in the lateral compartment and expose the ACL and lateral menisci to increased magnitude of anterior-directed shear and internal torque of the tibia relative to the femur. If this relationship exists, loading of the ACL and meniscus during a traumatic event would also depend on geometry of the articular surfaces of the tibiofemoral joint such as the posterior-inferior–directed slope of the tibial plateau and height and location of the tibial spines.

Our study focused on young healthy athletes who sustained their first significant knee trauma involving the ACL and did not remain active in sport before ACLR by a board-certified, sports medicine fellowship trained orthopaedic surgeon. Initially, 50% of our study participants underwent ACLR (at which time the status of the meniscus was assessed) within 7 weeks after the index trauma and 90% underwent ACLR within 15 weeks. Although identification of concomitant meniscal injury closer to the time of the index ACL trauma is preferable, we did not find a relationship between prevalence of meniscal injury and the time from injury to ACLR (Supplemental Table S2). We also examined the potential impact of differences in time to surgery on our results by conducting additional logistic regressions analysis with categories of time to surgery included as a covariate, and there were negligible differences between the original ORs (Table 4) and ORs adjusted for the time between injury and surgery (Supplemental Table S3). Therefore, we are confident that most, if not all, of the meniscal injuries occurred at the same time as the index ACL trauma. Consequently, our findings may not apply to older people who sustain an ACL injury and may have a degenerative tear of their meniscus.

Our previous work demonstrated a high correlation in joint laxity and lower extremity alignment measurements made on right and left knees of subjects with normal knees and no history of injury.⁴⁹ This supports the use of measurements made on the contralateral knee as surrogates for the injured knee before the trauma. However, in this study, measurements were made on the normal, contralateral knee after ACLR, so it is possible that they were modified by the injury, surgery, and rehabilitation.

The intersegmental loads transmitted across the patellofemoral and tibiofemoral joints at the time of injury are not only complex but also the magnitude and directions of the loads may vary widely for each injury. Combined ACL and meniscal trauma may be associated with sagittal and coronal plane anatomic alignment and consequently how forces are transmitted across both joints at the time of injury. Our results indicate that anatomic alignment of both patellofemoral and tibiofemoral joints is associated with risk of ACL and concomitant meniscal injury in female patients, but not in male patients. For male patients, it may be that navicular drop, and therefore anatomic alignment of foot/ankle complex, has a more pronounced influence on how loads and torques are transmitted across the knee. Future work that includes geometric characteristics of the knee such as the posterior slope of the tibial plateau is needed to test this hypothesis, as an increase in plateau slope is associated with an increased risk of sustaining an ACL injury. It is possible that slope of the medial and lateral compartments of the plateau have an influence on the type and extent of concomitant meniscal injury associated with ACL disruption and may help explain some of the differences we observed between male and female patients.

The risk of sustaining an ACL disruption with concomitant meniscal injury depends on both the risk of ACL injury, as well as the likelihood that a person with an ACL injury will have concomitant meniscal injury. Combining our current results with those from previous studies of sex-specific ACL injury risk factors in similar subjects enabled us to draw inferences about how the risk factors influence the overall risk of sustaining a first-time ACL injury with concomitant meniscal injury. The findings provide an important first step in identifying which uninjured young athletes may be at increased risk of sustaining this serious injury and in subsequently developing interventions to mitigate that risk. These findings also provide insight into the mechanisms underlying combined ACL and meniscal injuries, which is important for improving the approaches used to surgically repair/reconstruct and rehabilitate patients who sustain these severe injuries.

Conclusion

For female athletes, risk factors that have been associated previously with ACL injury, such as lower extremity alignment and increased genu recurvatum, are also associated with concomitant meniscal injury while others, including BMI and joint laxity, were not. Among male athletes, increased time spent participating in sport and navicular drop were associated with concomitant meniscal injury. Risk assessment and injury prevention strategies for knee injury should therefore consider the sex-specific effects of risk factors on both ACL and concomitant meniscal injury.

Supplemental Material

sj-pdf-1-ojs-10.1177_23259671231196492 – Supplemental material for Risk Factors for Concomitant Meniscal Injury With Sport-Related Anterior Cruciate Ligament Injury

Supplemental material, sj-pdf-1-ojs-10.1177_23259671231196492 for Risk Factors for Concomitant Meniscal Injury With Sport-Related Anterior Cruciate Ligament Injury by Hailee Reist, Pamela M. Vacek, Nathan Endres, Timothy W. Tourville, Mathew Failla, Andrew Geeslin, Matthew Geeslin, Andy Borah, Mickey Krug, Rebecca Choquette, Mike Toth and Bruce D. Beynnon in Orthopaedic Journal of Sports Medicine

Footnotes

Acknowledgements

The authors thank the volunteers who dedicated their valuable time to this study.

Final revision submitted May 26, 2023; accepted June 7, 2023.

One or more of the authors has declared the following potential conflict of interest or source of funding: this investigation was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the United States National Institutes of Health (grant RO1 AR050421). A.G. has received education payments from Arthrex, consulting fees from Smith & Nephew, nonconsulting fees from Arthrex and Smith & Nephew, and hospitality payments from Stryker. 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 University of Vermont (No. 00000485).

Supplemental Material

Supplemental Material for this article is available at .

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