In previous studies, good results have been reported after arthroscopic treatment of popliteal cysts and concomitant intra-articular pathology. However, only a few studies have reported the associated factors with residual popliteal cysts. The aim of this study was to examine the clinical and radiographic outcomes and investigate the factors associated with the recurrence of popliteal cyst after arthroscopic cyst decompression and cyst wall resection.

The authors hypothesized that residual popliteal cyst after arthroscopic decompression and cystectomy would be associated with degenerative cartilage lesions.

From December 2010 to December 2018, 54 patients with popliteal cysts were treated with arthroscopic decompression and cyst wall resection through an additional posteromedial cystic portal. Magnetic resonance imaging (MRI) or ultrasonography was used to observe whether the popliteal cyst had disappeared or decreased. The maximum diameter of the popliteal cyst was measured after surgery. The patients were classified into the disappeared and reduced groups according to the treatment outcome. Age, sex, symptom duration, preoperative degenerative changes based on the Kellgren–Lawrence (K-L) grade, cartilage lesions according to the International Cartilage Repair Society (ICRS) grades, synovitis, functional outcomes, and associated intra-articular lesions were compared between the two groups. The functional outcome was evaluated on the basis of the Rauschning and Lindgren knee score. The study included 22 men and 32 women, with mean age of 49.6years (range: 5–82years). According to the ICRS grade system, 28 (51.8%) patients had grade 0 to II, 26 (48.2%) patients had grade III to IV.

Follow-up radiographic evaluation revealed that the cyst had completely disappeared in 20 patients (37%) and reduced in size in 34 (63%). The mean cyst size was decreased significantly from 5.7cm (range: 1.7–15cm) to 1.7cm (range: 0–6.4cm), and the Rauschning and Lindgren knee score showed improved clinical features in all the patients. Between the disappeared and reduced groups, the presence of degenerative cartilage lesions (p=0.022, odds ratio 8.702, 95% confidence interval: 1.368–55.362) showed a statistically significant differences.

Through the posteromedial cystic portal, cysts were completely removed in approximately 40% of patients, and the size was reduced in 60% of patients. Presence of degenerative cartilage lesion represents an associated risk factor for residual popliteal cyst. These findings could be helpful in ensuring explaining poor prognostic factors.

IIIb; retrospective cohort study.