Ultrasound guided percutaneous treatment and follow-up of Baker's cyst in knee osteoarthritis.

OBJECTIVE Purpose of this study is to assess sonographic changes and clinical response in different subgroups of Baker's cyst patients with knee osteoarthritis after a single session of ultrasound-guided percutaneous aspiration and corticosteroid injection. MATERIALS AND METHODS Thirty-two knee osteoarthritis patients (46-85 years, mean 58.97±9.88) with symptomatic Baker's cyst diagnosed at ultrasonography were included in the study. To determine the grade of the symptoms, Visual Analogue Scale was applied. The patients were grouped in two, as simple (n=24) and complex (n=8) Baker's cyst. Thirty-two ultrasound-guided cyst aspirations concomitant 1 ml betamethasone injection (24 simple, 8 complex subgroups) were performed. Patients were followed clinically as well as via ultrasonography for 6 months after procedures. RESULTS A significant decrease in volume of the Baker's cysts after percutaneous treatment was accompanied by a significant clinical improvement. Moreover, the volume reduction of Baker's cyst after the treatment was significantly correlated with the clinical improvement (Pearson correlation coefficient=0.542, p=0.001). All 6 Baker's cysts relapsed at ultrasonography were complex type. Furthermore, a comparison of patients with simple Baker's cysts and those with complex Baker's cysts demonstrated no significant change in Visual Analogue Scale scores between two groups (p=0.061, Mann-Whitney U). No complications (minor or major) occurred secondary to percutaneous treatment. CONCLUSION Baker's cysts can be grouped as simple and complex groups via ultrasonography prior to the treatment. Cyst aspiration with ultrasound-guided corticosteroid injection yields clinical improvement and cyst volume reduction in all subgroups of patients with Baker's cyst secondary to knee osteoarthritis.