Arthroscopic surgery for meniscal tears is one of the most common procedures performed annually in the United States.1 In general, meniscal tears are less common in females than in males2; however, information regarding isolated tears of the meniscus in stable knees (ie, without cruciate ligament tears), specifically in a younger population, is scarce. Terzidis et al3 reported 81 (21.4%) of 378 young female athletes with isolated meniscal tears at arthroscopy, with most of the tears involving the medial meniscus. Metcalf and Barrett4 studied 1485 meniscal tear patterns in stable knees; in a group of patients younger than 40 years, 20% were females, and 62% of the tears involved the medial meniscus.
In young and active patients, meniscal tears are usually related to trauma or overuse injuries. Surgical treatment is preferred for these patients to gain quick recovery with early return to work and sports. However, at this age, the diagnosis of meniscal tear may be misled by other sources of knee pain, such as patellofemoral pain,5 or by anatomical variants or imaging artifacts that may appear as meniscal tears on magnetic resonance imaging (MRI).6 Common examples of increased intrameniscal signal that are not actual meniscus tears can be found in asymptomatic children that presumed to reflect normal vascularity and also in a meniscal contusion after acute trauma. Therefore, it may be that some of the patients referred to arthroscopy actually have unremarkable menisci.
The goal of this study was to report the prevalence and sex variance of isolated meniscal tears in a younger population based on arthroscopic findings. The hypothesis was that the prevalence of isolated tears of the meniscus in young females is low.
Materials and Methods
Institutional review board approval was obtained before beginning this study. To report the prevalence of meniscal tears in stable knees, the study included young patients who had undergone knee arthroscopy with intact cruciate ligaments at surgery. Patients who had concurrent osteotomy, patellar realignment, surgery for synovial disease (eg, rheumatoid arthritis, pigmented villonodular synovitis), or ipsilateral knee surgery were excluded. Information was retrieved from patients’ charts and surgical reports.
All preoperative evaluations and operations were undertaken and reported by 3 senior orthopedic surgeons (B.H., S.B., R.T.) who are experienced in knee arthroscopy and who work together at the same unit. The unit is a regional referral center for arthroscopic knee surgery. In the case of diagnosed meniscal tear, the indication for knee arthroscopy was an active patient with unresolved knee pain and activity limitation for at least 6 weeks. Arthroscopy for the treatment of painful knee with no meniscal tear that was suspected for chondral lesion was performed if a long period of activity limitation and physical therapy had failed (at least 6 months). All candidates underwent plain radiography and MRI of the knee preoperatively.
A total of 2425 arthroscopic and arthroscopic-assisted knee surgeries were performed at the authors’ institution between January 2007 and January 2013. Of these, 1146 were performed in patients younger than 40 years. Of these, 443 were excluded because of ligamentous injuries, 64 because of previous knee surgery, 20 because of patellar realignment, 3 because of osteotomy, and 25 because of synovial disease. Overall, 591 patients (480 males and 111 females) were included in this study. Mean patient age was 28.1 years (range, 13.1–39.9 years). Males and females were each divided into 5 age groups: 20 years or younger, 21 to 25 years, 26 to 30 years, 31 to 35 years, and 36 to 40 years.
Each age group was subdivided according to the following types of surgical findings: medial meniscal tear, lateral meniscus tear, both menisci tears, and no meniscal tear.
Measures included the prevalence of meniscal tears according to sex and age groups from the database of knee arthroscopies. Odds ratios were calculated to compare the presence of meniscal tears between sexes.
Of the 591 young patients with stable knees (ie, without ligamental injury) who underwent arthroscopic surgery, 445 (75.3%) had meniscal tears and 147 (24.7%) had none (Table 1). There were 383 (64.8%) meniscal tears observed in males and 62 (10.5%) observed in females. There were 254 (43%) tears of the medial meniscus, 175 (29.6%) tears of the lateral meniscus, and 16 (2.7%) tears of both menisci.
Prevalence of Meniscal Tears in Stable Knees
In males, the number of medial meniscal tears increased with age (Table 1). The number of lateral meniscal tears was higher than that of medial meniscal tears in patients younger than 25 years (84 lateral vs 51 medial) and decreased thereafter.
In females, the number of meniscal tears was low in all age groups. Specifically, a low prevalence of isolated medial meniscal tears (6 of 591; 1.0%) was found in females younger than 30 years compared with males (87 of 591; 14.7%).
Noteworthy is the relatively high number of stable knees without meniscal tear at arthroscopy in all age groups. The pathologies documented in knees without meniscal tear were low-grade chondral lesions (International Cartilage Repair Society classification 1 to 27; n=90), medial plica (n=10), and osteochondral defects (n=30). There were 16 knee arthroscopies with no remarkable pathology.
The odds ratio for having a meniscal tear, particularly of the medial meniscus, was significantly higher in males compared with females (Table 2).
Odds Ratios for Meniscal Tears in Young Patients With Stable Knees
The most clinically significant finding of the current study is the low prevalence of isolated medial meniscal tears among females younger than 30 years. Of 2425 arthroscopic and arthroscopic-assisted knee surgeries performed over a period of 6 years, only 6 females (compared with 87 males) younger than 30 years had an isolated medial meniscal tear. The odds ratio for having a medial meniscal tear in this young population was significantly higher in males vs females. The results suggest a protective mechanism for isolated medial meniscal tears in younger females as opposed to other injuries of the knee, such as anterior cruciate ligament (ACL) tears. The prevalence of medial meniscal tears increased with age.
Studies that analyzed the outcome of partial meniscectomies showed a low prevalence of meniscal tears in females compared with males,2 but few have shown the overall prevalence of isolated medial meniscal tears, specifically in younger patients with stable knees.3,4
Studies on male and female athletes have highlighted sex differences in activity level,8 anatomy,9,10 neuromuscular control,11 and hormonal effects.12,13 These sex-based disparities were focused on noncontact ACL tears10,14,15 and anterior knee pain,16 with females sustaining these injuries more frequently than males. The same concepts behind the etiology of ACL tear and anterior knee pain in females may support the scarcity of medial meniscal tears. Theories on ACL injuries that compare females with males include baseline level of conditioning, lower extremity alignment, physiological laxity, pelvis width, tibial rotation, and foot alignment.17 It has been demonstrated that female patients landing from a drop jump have increased knee valgus and ankle pronation18,19; therefore, the extreme forces that act on the knee during an acute injury in a young female are more likely to cause ligamental failure prior to medial meniscal tear. Many researchers believe that females have a higher prevalence of patellofemoral pain because they display biomechanical risk factors such as increased static measures of Q-angle and increased dynamic measures of knee valgus angle, hip internal rotation angle, hip adduction moment, and knee valgus moment.20–23 In addition, females’ strength has been reported to be significantly weaker than males’ on measures of quadriceps, hip external rotation, hip extension, and hip abductor strength.24,25
Another important observation from the current study of knee arthroscopies was a considerable number of patients with no apparent cruciate ligament or meniscal tear at surgery (146 of 591) in whom at least 6 months of nonoperative treatment failed. Most of these patients were diagnosed with different grades of chondral lesions at arthroscopy, and 16 were unremarkable. Thus, the pain mechanism is not completely understood and may sometimes be attributed to extra-articular sources. Specifically in young patients with mild arthroscopic findings, it is possible that the pathophysiology of pain is somewhat analogous to that of patellofemoral syndrome, which is ascribed to misalignment and hyperlaxity together with overload or overuse as a triggering factor26; it may also be explained by a neural model.27
There are several limitations to this study. First is its retrospective design. Second is its heterogenic population. The authors’ aim was to evaluate the prevalence of isolated meniscal tears in young females from a general database, but results may differ in specific populations, such as professional athletes. Although this study lacks long-term follow-up outcome measures, it highlights some important observations that the authors believe are useful for clinical decision making. Future investigations should assess the source of chronic knee pain in young females.
Isolated medial meniscal tears in stable knees are uncommon in females younger than 30 years; thus, young females with suspected tears should be reevaluated and treated conservatively before considering surgical solutions.
- Garrett WE Jr, Swiontkowski MF, Weinstein JN, et al. American Board of Orthopaedic Surgery Practice of the Orthopaedic Surgeon: Part II. Certification examination case mix. J Bone Joint Surg Am. 2006; 88:660–667. doi:10.2106/JBJS.E.01208 [CrossRef]
- Salata MJ, Gibbs AE, Sekiya JK. A systematic review of clinical outcomes in patients undergoing meniscectomy. Am J Sports Med. 2010; 38:1907–1916. doi:10.1177/0363546510370196 [CrossRef]
- Terzidis IP, Christodoulou A, Ploumis A, Givissis P, Natsis K, Koimtzis M. Meniscal tear characteristics in young athletes with a stable knee: arthroscopic evaluation. Am J Sports Med. 2006; 34:1170–1175. doi:10.1177/0363546506287939 [CrossRef]
- Metcalf MH, Barrett GR. Prospective evaluation of 1485 meniscal tear patterns in patients with stable knees. Am J Sports Med. 2004; 32(3):675–680. doi:10.1177/0095399703258743 [CrossRef]
- Lankhorst NE, Bierma-Zeinstra SM, van Middelkoop M. Factors associated with patellofemoral pain syndrome: a systematic review. Br J Sports Med. 2013; 47:193–206. doi:10.1136/bjsports-2011-090369 [CrossRef]
- Van Dyck P, Gielen J, D’Anvers J, et al. MR diagnosis of meniscal tears of the knee: analysis of error patterns. Arch Orthop Trauma Surg. 2007; 127:849–854. doi:10.1007/s00402-007-0318-7 [CrossRef]
- Brittberg M, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Joint Surg Am. 2003; 85:58–69.
- Dugan SA. Sports-related knee injuries in female athletes: what gives?Am J Phys Med Rehabil. 2005; 84(2):122–130. doi:10.1097/01.PHM.0000154183.40640.93 [CrossRef]
- Conley S, Rosenberg A, Crowninshield R. The female knee: anatomic variations. J Am Acad Orthop Surg. 2007; 15(suppl 1):S31–S36.
- McLean SG, Lucey SM, Rohrer S, Brandon C. Knee joint anatomy predicts high-risk in vivo dynamic landing knee biomechanics. Clin Biomech (Bristol, Avon). 2010; 25(8):781–788. doi:10.1016/j.clinbiomech.2010.06.002 [CrossRef]
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- Slauterbeck JR, Hardy DM. Sex hormones and knee ligament injuries in female athletes. Am J Med Sci. 2001; 322(4):196–199. doi:10.1097/00000441-200110000-00008 [CrossRef]
- Park SK, Stefanyshyn DJ, Loitz-Ramage B, Hart DA, Ronsky JL. Changing hormone levels during the menstrual cycle affect knee laxity and stiffness in healthy female subjects. Am J Sports Med. 2009; 37(3):588–598. doi:10.1177/0363546508326713 [CrossRef]
- Hewett TE, Myer GD, Ford KR. Reducing knee and anterior cruciate ligament injuries among female athletes: a systematic review of neuromuscular training interventions. J Knee Surg. 2005; 18(1):82–88.
- Imwalle LE, Myer GD, Ford KR, Hewett TE. Relationship between hip and knee kinematics in athletic women during cutting maneuvers: a possible link to noncontact anterior cruciate ligament injury and prevention. J Strength Cond Res. 2009; 23(8):2223–2230. doi:10.1519/JSC.0b013e3181bc1a02 [CrossRef]
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- Joseph M, Tiberio D, Baird JL, et al. Knee valgus during drop jumps in National Collegiate Athletic Association Division I female athletes: the effect of a medial post. Am J Sports Med. 2008; 36(2):285–289. doi:10.1177/0363546507308362 [CrossRef]
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- Malinzak RA, Colby SM, Kirkendall DT, Yu B, Garrett WE. A comparison of knee joint motion patterns between men and women in selected athletic tasks. Clin Biomech. 2001; 16:438–445. doi:10.1016/S0268-0033(01)00019-5 [CrossRef]
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- Boling M, Padua D, Marshall S, et al. Gender differences in the incidence and prevalence of patellofemoral pain syndrome. Scand J Med Sci Sports. 2010; 20(5):725–730. doi:10.1111/j.1600-0838.2009.00996.x [CrossRef]
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Prevalence of Meniscal Tears in Stable Knees
|Age, y||No. (%)|
|≤20||15 (2.5)||2 (0.3)||37 (6.3)||9 (1.5)||1 (0.2)||1 (0.2)||21 (3.6)||12 (2)||98 (16.6)|
|21–25||36 (6.1)||2 (0.3)||47 (8)||5 (0.8)||1 (0.2)||0 (0)||26 (4.4)||13 (2.2)||130 (22)|
|26–30||36 (6.1)||2 (0.3)||33 (5.6)||3 (0.5)||3 (0.5)||0 (0)||18 (3)||8 (1.4)||103 (17.4)|
|31–35||54 (9.1)||7 (1.2)||20 (3.4)||9 (1.5)||4 (0.7)||0 (0)||22 (3.7)||8 (1.4)||124 (21)|
|36–40||85 (14.4)||15 (2.5)||6 (1)||6 (1)||5 (0.8)||1 (0.2)||10 (1.7)||8 (1.4)||136 (23)|
|Total||226 (38.2)||28 (4.7)||143 (24.2)||32 (5.4)||14 (2.4)||2 (0.3)||97 (16.4)||49 (8.3)||591 (100)|
Odds Ratios for Meniscal Tears in Young Patients With Stable Knees
|Sex||OR (95% CI)|
|Male||3.95 (1.63–9.56)||1.75 (0.95–3.25)||0.22 (0.12–0.41)|
|Female||0.25 (0.1–0.61)||0.57 (0.31–1.05)||4.42 (2.44–8.01)|