Discoid lateral meniscus (DLM) is not a rare morphologic. Results of Subtotal/Total or Partial Meniscectomy for Discoid Lateral Meniscus in Children

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1 Results of Subtotal/Total or Partial Meniscectomy for Discoid Lateral Meniscus in Children Dae-Hee Lee, M.D., Tae-Ho Kim, M.D., Jong-Min Kim, M.D., and Seong-Il Bin, M.D. Purpose: The purpose of this study was to compare the midterm outcomes of subtotal/total meniscectomy with those of partial meniscectomy for symptomatic torn discoid lateral meniscus (DLM) in children and evaluate the correlation of chondral wear in the lateral compartment at index surgery with arthritic changes at final follow-up. Methods: We reviewed 43 knees in 36 patients aged less than 15 years who underwent arthroscopic procedures for torn DLMs between 1999 and The mean patient age at the time of surgery was 9.5 years (range, 5 to 14 years), and the mean follow-up period was 4.3 years (range, 2.1 to 9.4 years). Of the 43 knees, 23 underwent partial meniscectomy and 20 underwent subtotal/total meniscectomy. The status of the articular cartilage at the time of surgery was analyzed with the Outerbridge grading system, and radiologic arthritic changes of the lateral compartment at final follow-up were evaluated by use of the classification of Tapper and Hoover. Results: Clinically excellent or good results at final follow-up were observed in 36 of 43 knees (83.7%). There was no difference between the partial and subtotal/total meniscectomy groups in terms of the presence of chondromalacia of the lateral compartment at the time of surgery. Radiologic arthritic changes at final follow-up were significantly more severe in the subtotal/total meniscectomy group than in the partial meniscectomy group (P.001). We observed a positive linear association between the degree of chondral wear of the lateral tibial plateau at the time of surgery and subsequent development of radiologic signs of arthritic change at last follow-up (.628, P.027). We also found a correlation between symptom duration and chondromalacia of the lateral tibial plateau (.684, P.021). Conclusions: Although there were no differences in clinical results between the partial and subtotal/total meniscectomy groups, partial meniscectomy yielded better radiologic results than subtotal/total meniscectomy for torn DLMs in children. Our findings suggest the need for early diagnosis and greater caution in the treatment of torn DLMs in children. Level of Evidence: Level IV, therapeutic case series. Key Words: Discoid meniscus Meniscectomy Children Cartilage damage Osteoarthritis. Discoid lateral meniscus (DLM) is not a rare morphologic anomaly in Asia. 1-4 Caution is required when treating children with torn DLMs because of From the Department of Orthopaedic Surgery, Korea University School of Medicine, Anam Hospital (D.-H.L.); Department of Orthopaedic Surgery, Cheong-ju St Mary s Hospital, College of Medicine, Catholic University (T.-H.K.); and Department of Orthopedic Surgery, University of Ulsan, College of Medicine, Asan Medical Center (J.-M.K., S.-I.B.), Seoul, South Korea. Supported by the Korean Science and Engineering Foundation grant funded by the Korean government (MESt) (No. R ). The authors report no conflict of interest. Received July 24, 2008; accepted October 26, Address correspondence and reprint requests to Seong-Il Bin, M.D., Department of Orthopedic Surgery, University of Ulsan, College of Medicine, Asan Medical Center, 388-1, Poongnap-2dong, Songpa-gu, Seoul, , South Korea. sibin@amc.seoul.kr 2009 by the Arthroscopy Association of North America /09/ $36.00/0 doi: /j.arthro unavoidable further arthritic changes caused by poor vascularity, 5 lack of normal collagen arrangement, 6,7 and the effects of the meniscal tear. Premature arthritis is common in patients who undergo total meniscectomy during childhood, so meniscus-preserving procedures such as partial meniscectomy are preferred in children with torn DLMs Nevertheless, some menisci require total resection because of the tear pattern, delays in treatment, or neglected severe tears. Contrary to general expectations, satisfactory long-term results after total meniscectomy have been reported in children with torn DLMs with or without associated arthritic changes. 12,13 Thus the ideal treatment for torn DLMs in children has not been determined. Most previous investigations in children with torn DLMs did not compare one treatment option (e.g., partial meniscectomy) directly with another (e.g., total meniscectomy); rather, most of these studies assessed 496 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 5 (May), 2009: pp

2 TORN DISCOID LATERAL MENISCUS IN CHILDREN 497 outcomes from one treatment option and compared their results with those of other studies. 4,12,14-16 Moreover, most have reported relatively good results with respect to further arthritic changes, even after longterm follow-up periods. 17 In addition, studies comparing the outcomes of total and partial meniscectomy in adults did not assess chondral wear status at the time of surgery. 18 On the basis of our experience, chondral wear at the time of surgery is severe, relative to patient age, especially in patients undergoing subtotal/total meniscectomy. Moreover, these patients showed aggravated arthritic changes on radiographs at midterm followup. The purpose of this study was to compare the clinico-radiologic results of subtotal/total and partial meniscectomy for symptomatic torn DLMs in children and evaluate the correlation between chondral wear of the lateral compartment at the time of surgery with arthritic changes at final follow-up. The hypotheses of this study were that the arthritic changes at last follow-up after subtotal or total meniscectomy could be more severe than those after partial meniscectomy and that chondral wear of the lateral compartment at the time of surgery might be a predictor of further arthritic changes after arthroscopic partial or subtotal/total meniscectomy. The inclusion criteria for this study were as follows: Patients must have undergone arthroscopic subtotal/ total or partial meniscectomy for torn DLMs, they must be aged less than 15 years, and they must have been followed up for more than 2 years. Those patients who did have more than 2 years of follow-up or who had previous operations or concomitant knee surgery, such as ligament reconstruction, medial meniscectomy, or lateral meniscectomy with repair of the affected knee, were excluded. Of the total of 1,586 arthroscopic knee procedures performed at our institution by the senior author between April 1999 and December 2004, 54 (1.9%) were performed on torn DLMs in children aged less than 15 years. Of these children, 5 were excluded because of previous or concomitant surgery (3 partial meniscectomies with repair, 1 anterior cruciate ligament reconstruction, and 1 partial meniscectomy for medial meniscus tear). Six patients were lost to follow-up, three immediately after surgery and three who had emigrated to other countries. Therefore the medical records and radiographs of the remaining 43 knees in 36 patients were retrospectively reviewed. Data assessed included gender, age at the time of surgery, type and duration of preoperative symptoms and signs, and duration of follow-up. Arthroscopic findings were recorded consistently by use of a preformatted electronic document (knee documentation system) (Fig 1A). On the basis of the remnant width of the meniscus after meniscectomy (Fig 1B) and the knee documentation system, we classified 23 knees as having undergone partial meniscectomy and 20 as having undergone subtotal/total meniscectomy. Subtotal meniscectomy was defined as meniscectomy with 3 mm of the peripheral meniscus (25% of the total meniscus width) remaining. Resec- METHODS. FIGURE 1. (A) Sample of preformatted electronic medical records for arthroscopic evaluation (knee documentation system). (B) Sample showing arthroscopic findings of meniscus and surgical contents (tear pattern, remaining rim according to location after meniscectomy) by use of electronic drawing system.

3 498 D-H. LEE ET AL. tion to a greater degree was considered to be a total meniscectomy, and other resections were defined as partial meniscectomies. Each DLM was classified as complete, incomplete, or Wrisberg type based on the classification of Watanabe et al. 19 DLM tear patterns were categorized as horizontal (simple or complicated), longitudinal (including bucket-handle tear), radial, or complex. 20 The severity of associated cartilage damage in the lateral compartment at the time of surgery was graded according to the Outerbridge classification. 21 Arthroscopic surgery was indicated for symptomatic patients with recurrent locking (snapping or clicking), persistent pain, limitation of knee motion, or limping gait. In contrast, asymptomatic DLMs, usually found incidentally on magnetic resonance imaging, were not treated. Before the operation, we made an effort to decide whether subtotal/total or partial meniscectomy was appropriate, considering the tear pattern (e.g., intrasubstance tear) and degeneration of the remaining meniscus (as inferred from intrameniscal signal intensity on magnetic resonance imaging). Surgery for DLM tears included preservation of intact meniscal tissue, when possible; removal of only the unstable part of the meniscus causing symptoms; saucerization to create a normal configuration; and careful trimming of the remaining rim without damaging the adjacent articular cartilage to prevent further tearing. 22 All procedures were performed with a pneumatic tourniquet with the patient under general anesthesia. Routine arthroscopic examination of the joint began with the 30 oblique arthroscope in the anterolateral portal and the probe in the anteromedial portals. In making an anteromedial working portal, the spinal needle was inserted toward the lateral joint space, targeting the DLM tear site, while consistent varus stress was applied to the joint with the leg in a figure-4 position. This technique effectively anticipated and increased the available working space that could be reached by the punch to debride the tear site for meniscectomy and to visualize the lateral compartment more easily. The meniscus was carefully visualized and probed to detect the tear pattern. After the decision of whether to perform a partial or subtotal/ total meniscectomy was made based on the tear pattern and degenerative changes of the tear margin, the meniscectomy was performed in a piecemeal or morcellation manner by use of arthroscopic instruments such as a basket punch, rotary scissors, or a motorized meniscal shaver while changing the portal from anteromedial to anterolateral or sometimes to another portal. In case of partial meniscectomy, arthroscopic saucerization was done to debride the discoid meniscus to a peripheral rim of 7 to 8 mm, because resection to a width in excess of 8 mm was thought to increase the risk of recurrent tear. 9 Finally, the thick discoid meniscus tissue was reshaped into a thinner, normallooking meniscus. Postoperative clinical outcomes were analyzed by use of the Ikeuchi grading system 23 and classified as excellent (full range of motion, no knee snapping, and no pain), good (infrequent pain with exertion and full range of motion), fair (slight pain, knee snapping on motion, and full range of knee motion), or poor (constant pain and/or recurrent locking of knee). In cases of bilateral discoid menisci, patients were asked to identify the more painful knee. If the patient complained of similar pain in both knees, symptoms were correlated with physical examination data (effusion, joint line tenderness) to minimize the bias effect, whereby only 1 symptomatic knee of both knees may artifactually result in a negative clinical score for both knees. Standing anteroposterior radiographs, posteroanterior radiographs with 45 of flexion, and lateral radiographs of the knee joint were taken at the last follow-up. Arthritic changes of the lateral compartment were evaluated based on the classification of Tapper and Hoover 24 : grade 0, normal; grade I, squaring of the tibial margin; grade II, flattening of the femoral condyle and squaring and sclerosis of the tibial plateau; grade III, narrowing of the joint space and/or hypertrophic change; and grade IV, a combination of grade I, II, and III changes to a more severe degree. When considering narrowing of the joint space, we usually evaluated this parameter on the standing posteroanterior view with 45 of flexion, including comparison with the opposite side in unilateral cases, but we compared medial joint spaces in 7 bilateral cases. Because we evaluated radiography findings using both preoperative and latest follow-up data as controls, any error introduced as a result of magnification would be the same for both the involved and uninvolved knee or compartment. All the radiologic evaluations were performed by an orthopaedic surgeon blinded to the type of surgery the patients underwent. Statistical analysis was performed with SPSS software for Windows, version 12.0 (SPSS, Chicago, IL). Clinical outcomes, arthroscopic findings, and radiologic data in the 2 groups were compared by use of the Fisher exact test. Correlation between arthritic changes at final follow-up and chondral wear of the lateral compartment at the time of surgery was assessed by use of the Spearman 2-sided test. Correlation of symptom duration with chondral wear of the lateral compartment was also as-

4 TORN DISCOID LATERAL MENISCUS IN CHILDREN 499 TABLE 1. Demographic Data of Total and Partial Meniscectomy Groups Total Meniscectomy Partial Meniscectomy Method of Statistical Analysis P Value Mean age (yr) Student t test.693 Male/female 12/8 8/15 2 Test.131 Left/right 8/12 10/13 2 Test.818 Complete/incomplete 16/4 20/3 2 Test.687 Duration of symptoms (mo) Student t test.693 Duration of follow-up (mo) Student t test.067 sessed by use of the Spearman 2-sided test. P.05 was considered statistically significant. RESULTS Overall Demographic Data, Type, Tear Pattern, and Preoperative Symptoms TABLE 2. Clinical Results of DLM According to Ikeuchi Grading Scale Ikeuchi Grade Poor Fair Good Excellent Total Subtotal/total meniscectomy Partial meniscectomy Total The 43 knees in the 36 children showed no gender preponderance (20 male and 23 female patients). Of the 36 patients, 7 (19.4%) had bilateral torn DLMs. The mean patient age at the time of surgery was 9.5 years (range, 5 to 14 years), and the mean follow-up period was 4.3 years (range, 2.1 to 9.4 years). The mean duration of symptoms before arthroscopic surgery was 9.4 months (range, 2 to 55 months). The most frequent preoperative symptom was limitation of motion (28 knees [65.1%]), followed by pain (9 knees [20.9%]), clicking or snapping (4 knees [9.3%]), and limping gait (2 knees [4.7%]). On the basis of the classification of Watanabe et al., knees (83.7%) had complete DLMs and 7 (16.3%) had incomplete DLMs; none of the knees had Wrisberg-type DLMs. One patient had a medial incomplete discoid meniscus without tear and a torn lateral complete discoid meniscus in the same knee. Of the knees, 17 showed longitudinal tear patterns, including bucket-handle tears; 14 showed complex patterns; 4 showed complicated horizontal patterns; 6 showed simple horizontal patterns; and 2 showed radial tears. The demographic data, type of DLM, postoperative follow-up period, and duration of symptoms before surgery did not differ significantly between the subtotal/ total and partial meniscectomy groups (Table 1). Clinical Outcomes According to the scale of Ikeuchi, 36 of the 43 knees (83.7%) showed clinically excellent or good results at final follow-up, 20 of 23 (86.9%) in the partial meniscectomy group and 16 of 20 (80%) in the subtotal/total meniscectomy group (P.166 by Fisher exact test) (Table 2). Articular Change at Time of Surgery and at Last Follow-up At the time of surgery, 14 of 23 knees (61%) in the partial meniscectomy group and 9 of 20 (45%) in the subtotal/total meniscectomy group had grade 0 chondromalacia of the lateral femoral condyle; 8 (35%) and 10 TABLE 3. Scoring of Knees in Subtotal/Total and Partial Groups According to Outerbridge Grade and Tapper and Hoover Grade Grade 0 I II III IV P Value OBG of lateral femoral condyle at time of operation.671 Subtotal/total Partial Total OBG of lateral tibia plateau at time of operation.926 Subtotal/total Partial Total THG on radiograph at last follow-up.001 Subtotal/total Partial Total Abbreviations: OBG, Outerbridge grade; THG, Tapper and Hoover grade.

5 500 D-H. LEE ET AL. (50%), respectively, had grade I chondromalacia; and 1 (4.3%) and 1 (5%), respectively, had grade II chondromalacia (P.671 by Fisher exact test). Grade 0 (normal) chondromalacia of the lateral tibial plateau was observed in 8 knees (35%) and 6 knees (30%) in the partial and subtotal/total meniscectomy groups, respectively; grade I or II chondromalacia was found in 14 (61%) and 13 (65%), respectively; and grade III chondromalacia was found in 1 (4%) and 1 (5%), respectively (Table 3). At final follow-up, grade 0 arthritic changes were observed in 7 of 43 knees (16%), 5 of 23 (22%) in the partial meniscectomy group and 2 of 20 (10%) in the subtotal/total meniscectomy group. Grade I was observed in 18 knees (42%), 15 (65%) in the partial meniscectomy group and 3 (15%) in the subtotal/total meniscectomy group. Grade II was observed in 11 knees (26%), 3 (13%) in the partial meniscectomy group and 8 (40%) in the subtotal/total meniscectomy group. Grade III was observed in 7 knees (16%), all of which (35%) were in the subtotal/total meniscectomy group. In other words, only 16% of patients had grade 0 arthritic changes on follow-up radiography. Therefore the remaining 84% of patients showed arthritic changes higher than grade I. The difference between the 2 groups was significant, indicating that more serious arthritic changes at latest follow-up occurred in the subtotal/total meniscectomy group than in the partial meniscectomy group (P.001). Correlations We observed a positive linear association between chondromalacia of the lateral tibial plateau at the time FIGURE 2. (A) Arthroscopic findings during total meniscectomy in 8-year-old female patient with torn DLM, showing cartilage erosion on lateral tibial plateau. (B) Preoperative radiograph showing intact knee joint. (C) Standing posteroanterior radiograph with 45 of flexion at 6 years follow-up, showing severe joint space narrowing (arrow) in lateral compartment. FIGURE 3. (A) Arthroscopic findings during partial meniscectomy in 9-year-old female patient with torn DLM, showing no chondral wear on lateral tibial plateau. (B) The preoperative radiograph also shows a normal knee joint. (C) At follow-up 4 years later, the standing posteroanterior radiograph with 45 of flexion shows a relatively preserved joint space.

6 TORN DISCOID LATERAL MENISCUS IN CHILDREN 501 of surgery and radiographically observed arthritic changes at last follow-up (Spearman 2-sided test,.628; P.027) (Figs 2 and 3). In addition, the duration of clinical symptoms was associated with cartilage wear of the lateral tibia plateau seen at the time of surgery (.684, P.021). No association, however, was found between chondromalacia of the lateral femoral condyle at the time of surgery and arthritic grade at last follow-up (.281, P.078) or between chondromalacia and duration of clinical symptoms (.183, P.284). There was also no correlation between Ikeuchi scale and articular grade at last follow-up (.342, P.633). The association between Outerbridge grade of the lateral femoral condyle and lateral tibial plateau and arthritic changes at last follow-up is shown in Table 4. The numbers of patients grouped by Outerbridge grade of the lateral compartment at the time of surgery, as assessed by the criteria of Tapper and Hoover, 24 are shown in Fig 4. DISCUSSION DLM is a common variation of the meniscus in Korea and Japan, with a reported incidence of 15% to 17%. 20,23,25 DLM is the most common reason for arthroscopic operations performed on children, 26 and early arthritic changes are inevitable, especially with tears, so it is important to determine the accurate clinical and radiologic long-term outcomes for DLMs in children. Although total meniscectomy had been the procedure of choice, meniscus-preserving procedures (partial meniscectomy) are now favored. Nevertheless, several recent studies have reported that the clinical and radiologic outcomes of total meniscectomy were superior or equal to those of partial meniscectomy. 12,13 Open total meniscectomy yielded excellent to good long-term clinical results (mean follow-up, 17 years), as determined by the scale of Ikeuchi, in 13 of 18 knees (76%) in children and adolescents (mean age, 10.5 years) with discoid menisci. 16 Similarly, 10 of 11 knees (90.9%) in children and adolescents (mean age, 14.6 years) showed excellent or good long-term results (mean follow-up, 13.4 years) after arthroscopic total meniscectomy. 12 We found that 16 of 20 knees (80%) in children (mean age, 10.5 years) who underwent subtotal/total meniscectomy were rated as excellent or good based on the scale of Ikeuchi, with a mean follow-up of 5.6 years. Late arthritic changes have been reported after total meniscectomy of DLMs in children. For example, 3 of 9 evaluable knees (33%) showed slight narrowing of the joint space and flattening of the lateral femoral condyle, 16 and 11 knees (100%) were rated radiographically as having grade I osteoarthritis without moderate or advanced degenerative changes. 12 In contrast, after open total meniscectomy in patients with a mean age of 9 years, 5 of 11 knees (45%) were grade 0 or I and 6 (45%) were grade III or IV after a mean TABLE 4. OBG at Time of Operation Correlation Between Outerbridge Grade at Time of Surgery and Arthritic Changes at Last Follow-up THG on Radiograph at Last Follow-up 0 I II III IV Total Correlation LFC.281,* P I II III IV Total LTP.628, P I II III IV Total Abbreviations: OBG, Outerbridge grade; THG, Tapper and Hoover grade; LFC, lateral femoral condyle; LTP, lateral tibial plateau. *Correlation coefficient of OBG of LFC at time of surgery with THG at last follow-up. Correlation coefficient of OBG of LTP at time of surgery with THG at last follow-up.

7 502 D-H. LEE ET AL. FIGURE 4. Numbers of patients with each Outerbridge (OB) grade of lateral femoral condyle (LFC) (A) and lateral tibial plateau (LTP) (B), based on criteria of Tapper and Hoover (TH). follow-up of 19.8 years. 15 We found that, of the 20 knees in the subtotal/total meniscectomy group, 6 (30%) were grade 0 or I, 8 (40%) were grade II, and 6 (30%) were grade III. Our results appear, at first glance, to be similar to those of previously reported studies. However, considering the shorter follow-up period of this study (5 years), we believe that worse outcomes in terms of radiographic degenerative changes may become evident after longer-term follow-up. Even though it is difficult to directly compare our results with previously reported data, it is very likely that our patients will present even more serious outcomes if we observe them for up to 20 years, as was done in previous case series. Regarding the results of partial meniscectomy in a recent study, of 11 knees in children (mean age, 11.5 years) who underwent arthroscopic partial meniscectomy, all were rated as excellent or good according to the scale of Ikeuchi, and no pathology was found radiographically, with a mean follow-up of 4.5 years. 14 We observed similar clinical outcomes, in that 20 of the 23 knees (86.9%) that underwent partial meniscectomy were graded as excellent or good on the scale of Ikeuchi. At last follow-up, however, only 5 knees (22%) had grade 0 osteoarthritis radiographically, whereas 15 (65%) were grade II and 3 (13%) were grade III in our study, indicating that our radiologic outcomes were poorer. As mentioned previously, considering the relatively short-term follow-up period of our study, these outcomes seem to be more severe than previously noted in the subtotal/total meniscectomy group if longer follow-up will be performed on our patients. The more serious results at follow-up may be related to chondral wear of the lateral compartment at the time of operation. None of the previous studies of the results of meniscectomy in children has described the preoperative status of chondral wear. Of the 43 knees assessed in this study, 20 (46.5%) had grade I or II chondromalacia of the lateral femoral condyle according to the Outerbridge classification and 29 (67.4%) had grade I, III, or III chondromalacia of the lateral tibial plateau, regardless of the extent of meniscectomy. Our findings indicate that chondromalacia of the lateral tibial plateau at the time of surgery correlated with more serious progression of osteoarthritic changes in children with torn DLMs who underwent subtotal/total or partial meniscectomy. Although 1 recent study reported a lower incidence and severity of chondromalacia at the time of surgery, all but 2 of these knees were treated with partial meniscectomy. 27 The more severe follow-up results we observed may be a result of selection bias, in that all of the knees had torn DLMs, which may have had delays in treatment or may have been missed by general physicians. In this study children in both groups had symptoms for more than 1 year (mean, 16.4 months in subtotal/total

8 TORN DISCOID LATERAL MENISCUS IN CHILDREN 503 meniscectomy group and 14.6 months in partial meniscectomy group). Our hospital is a tertiary referral center, and almost all patients are referred from local clinics for further management. The delay in diagnosis of the torn DLM allowed the meniscal tear to become more extensive, involving the peripheral capsule, and allowed aggravated degenerative changes of the tear margin and the lateral compartment to occur. In these patients total meniscectomy was unavoidable. Therefore the early diagnosis of torn DLMs in children can avoid much of the damage to the articular cartilage and may thus offer an additional benefit to the overall postoperative outcome. In addition, the importance of early diagnosis is supported by our data showing a correlation between symptom duration and chondral wear of the lateral tibial plateau at the time of surgery. This study had several limitations, including the absence of a control group, consisting of a group of comparable children who had DLMs without tears. We could therefore not determine whether the more serious results we observed were because of inherent abnormalities (e.g., poor vascularity, different collagen arrangements, or abnormal configuration and positioning) or DLM tears. Other limitations include the small number of patients, the retrospective design of the study, and the relatively short-term follow-up compared with previous long-term follow-up studies. However, this study is the first to compare the results of arthroscopic subtotal/total meniscectomy and partial meniscectomy performed by a single surgeon for torn DLMs in children. In addition, although this study was retrospective in design, arthroscopic findings were recorded prospectively. CONCLUSIONS Although there were no differences in clinical results between the partial and subtotal/total meniscectomy groups, partial meniscectomy yielded better radiologic results than subtotal/total meniscectomy for torn DLMs in children. Our findings suggest the need for early diagnosis and greater caution in the treatment of torn DLMs in children. REFERENCES 1. Hamada M, Shino K, Kawano K, Araki Y, Matsui Y, Doi T. Usefulness of magnetic resonance imaging for detecting intrasubstance tear and/or degeneration of lateral discoid meniscus. Arthroscopy 1994;10: Kim JM, Bin SI. Meniscal allograft transplantation after total meniscectomy of torn discoid lateral meniscus. Arthroscopy 2006;22: e1. Available online at 3. Nawata K, Teshima R, Ohno M, Takita T, Otuki K. Discoid lateral menisci in older patients. A radiographic study of 21 cases. Int Orthop 1999;23: Rao SK, Sripathi Rao P. Clinical, radiologic and arthroscopic assessment and treatment of bilateral discoid lateral meniscus. 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