Clinical and MRI outcomes after arthroscopic decompression for meniscal cysts according to cyst removal status

Meniscal cysts are commonly associated with horizontal meniscal tears, but their distribution, clinical significance, and postoperative changes remain unclear. This study aimed to evaluate clinical outcomes and postoperative magnetic resonance imaging (MRI) findings after arthroscopic treatment and to identify factors associated with incomplete cyst removal. A total of 73 meniscal cysts (73 patients, mean age 38.67 ± 13.98 years) were treated with arthroscopic meniscal surgery between June 2011 and August 2021, with a mean follow-up of 45.66 ± 23.31 months. Postoperative MRI was performed at a mean follow-up period of 17.53 ± 17.20 months. Associations between patient- and cyst-related factors and complete cyst removal were evaluated. A parsimonious multivariable logistic regression model including preoperative large cyst size (≥ 17 mm) and body mass index (BMI) was used to evaluate factors associated with incomplete cyst removal. Clinical outcomes, including Tegner activity, Lysholm knee, and Hospital for special surgery (HSS) scores, were evaluated. Postoperative MRI was available in 40 patients, of whom 33 patients (82.5%) showed complete cyst removal. Cyst size significantly decreased after surgery, with strong correlations between coronal and sagittal measurements on both preoperative and postoperative MRI ( p < 0.001). In univariate analysis, higher BMI was significantly associated with incomplete cyst removal ( p = 0.013). In the parsimonious multivariable logistic regression model, large preoperative cyst size (≥ 17 mm) and higher BMI were associated with a lower likelihood of complete cyst removal ( p = 0.020 and p = 0.015, respectively). Clinical outcomes improved significantly after surgery, with Lysholm and HSS scores showing significant increases in both the complete and incomplete cyst removal groups ( p < 0.05). However, no significant differences were observed between the two groups in clinical improvement. Arthroscopic decompression combined with meniscal surgery resulted in significant clinical improvement and marked improvement in MRI findings in patients with meniscal cysts. Although larger cyst size and higher BMI were associated with incomplete cyst removal, no significant differences in clinical outcomes were observed according to cyst removal status.