Background: Due to its abnormal morphology and ultrastructure, discoid lateral meniscus (DLM) is prone to tear and degeneration, leading to clinical symptoms. Arthroscopy is the main treatment for symptomatic DLM; however, postoperative outcomes vary widely due to the effects of diverse factors. This research aims to explore the factors influencing postoperative outcomes of symptomatic DLM. Methods: Patients with DLM who underwent arthroscopic surgery at our hospital from 9/2008 to 9/2015 were enrolled according to the inclusion and exclusion criteria. Fourteen variables, including sex, body mass index (BMI) and other variables, were chosen as factors for study. Knee function was assessed using the International Knee Documentation Committee (IKDC) score. Univariate analyses (Mann-Whitney U test or Kruskall-Wallis rank sum test) and multivariate analyses (ordinal logistic regression) were used to identify the factors that influenced postoperative outcomes. P < 0.05 was considered statistically significant. Results: A total of 502 patients, including 353 females (70.3%) and 149 males (29.7%), were enrolled. The median IKDC score postoperatively (87.4; range, 41.4~97.7; IQR, 14.6) was higher than that preoperatively (57.6; range, 26.9 64.9; IQR, 9.7) (P < 0.001). Male sex was predictive of a higher IKDC score (P = 0.023, OR = 1.702). Compared with BMI ≥25 kg/m 2 , < 18.5 kg/m 2 was associated with better IKDC score (P = 0.026, OR = 3.016). Contrasting with age of onset ≥45 years, ≤14 years (P < 0.001, OR = 20.780) and 14~25 years (P < 0.001, OR = 8.516) were associated with better IKDC score. In comparison with symptoms duration> 24 months, IKDC scores for patients with symptoms duration ≤1 month (P = 0.001, OR = 3.511), 1~6 months (P < 0.001, OR = 3.463) and 6~24 months (P < 0.001, OR = 3.254) were significantly elevated. Compared to Outerbridge grade III~IV, no injury (P < 0.001, OR = 6.379) and grade I (P = 0.01, OR = 4.332) were associated with higher IKDC score. Conclusions: Arthroscopic treatment of symptomatic DLM is safe and effective, but its clinical efficacy is affected by many factors. Specifically, male sex, BMI < 18.5 kg/m 2 , age of onset < 25 years (especially < 14 years) and symptoms duration < 24 months are conducive to good postoperative outcomes. However, combined articular cartilage injury (Outbridge grade ≥ 2) reduces postoperative effect.

Background: Discoid lateral meniscus (DLM) have a higher rate of tear and degeneration for its abnormal shape and structure. Arthroscopy is the main treatment for symptomatic DLM, however, postoperative clinical outcomes vary widely resulting from effects of diverse factors. Therefore, the present research aims to explore the factors influencing postoperative clinical outcomes of symptomatic DLM . Methods: Patients with discoid meniscus who underwent arthroscopic surgery at our hospital from 9/2008 to 9/2015 were selected according to the inclusion and exclusion criteria. Gender, body mass index (BMI) ,and 18 other factors were selected as potential predictors that might affect postoperative outcomes . Knee function was assessed by the Lysholm, Tegner, International Knee Documentation Committee (IKDC) and Ikeuchi scales. Univariate analyses (rank-sum test and chi-squared test) and multivariate analyses (ordered logistic regression and logistic regression) were used to detect the risk factors bearing on postoperative outcomes. P<0.05 was considered statistically significant. Results: A total of 502 patients were enrolled. Female gender was an influencing factor for Lysholm (P=0.002, odds ratio (OR) =2.713), Tegner (P=0.001, OR=2.526) , IKDC (P=0.022, OR=1.735) and Ikeuchi scores (P=0.010, OR=2.164). BMI was negatively correlated with Lysholm (P=0.007, OR=1.119) and IKDC (P=0.029, OR=1.088) scores. Work intensity was negatively related to IKDC (P=0.038, OR=1.492) and Ikeuchi (P=0.014, OR=1.689) scores. Age of onset was inversely correlated with Tegner (P<0.001, OR=1.109) score.Symptoms duration and IKDC (P=0.002, OR=1.020) had an inverse correlation. Lack of cartilage lesions was a protective factor in terms of Tegner score (P<0.001, OR=0.261). Outerbridge grade was negatively correlated with Lysholm (P=0.016, OR=1.589) and Ikeuchi (P=0.017, OR=1.582) scores. Saucerization with repair was a risk factor for poor Ikeuchi scores (P=0.037, OR=4.328) in terms of subtotal/total meniscectomy. Conclusion: Arthroscopic treatment of symptomatic DLM is safe and effective . Female sex, cartilage lesions and saucerization with repair may be related to unfavourable postoperative outcomes. Clinical efficacy may worsen with increasingBMI, work intensity, symptomatic duration, age of onset and Outerbridge grade.