Popliteal Cyst Aspiration and Injection: Does Location of the Corticosteroid Injection Matter?

Purpose or Learning Objective: Baker's cysts, also known as popliteal cysts, are common and can be treated with ultrasonography-guided aspiration and steroid injection via a posterior approach. In some cases, the referring physician may request the corticosteroid injection be done anteriorly into the knee joint, requiring repositioning, re-prepping, and an additional puncture site. Our study compared the efficacy of pain reduction between the single- and double-access techniques. We hypothesized no significant difference between the two approaches and would eliminate the need for a separate anterior injection and associated risks, such as increased possibility of infection and bleeding, greater anesthetic use, medical waste (sterile drapes, probe cover, etc.), and a longer appointment time.

Methods or Background: This case-control study approved by the institutional review board retrospectively examined patients who underwent either a single posterior aspiration and injection or a double-access approach aspiration/injection procedure between 2017 and 2022. All patients received 1 mL triamcinolone (40 mg/mL), but the anesthetic dose varied between the two groups. The primary outcome was self-reported pain levels before intervention, immediately after injection, and 14 days postinjection. Other variables evaluated were patient sex, age, calculated cyst volume, amount aspirated, fluid complexity, and Kellgren-Lawrence (KL) osteoarthritis grading.

Results or Findings: A total of 74 patients were included in the study. Group A consisted of 50 patients (38 women; mean age: 64.0 years) who underwent posterior cyst aspiration and injection. Group B consisted of 24 patients (12 women; mean age: 61.5 years) who received an anterior intra-articular knee joint injection after posterior cyst aspiration. Preinjection pain scores, as well as immediate postinjection and 2-week postinjection pain score changes, did not differ significantly between the two groups (Group A: 4.2, − 3.0, − 3.0; Group B: 5.0, − 3.2, − 3. 0; P = 0.09). Furthermore, no significant differences were observed between the two groups regarding age, sex, laterality, cyst size, aspiration volume, fluid complexity, or KL grade.

Conclusion: Our study found no difference in self-reported pain reduction immediately after injection and 14 days later between patients who underwent posterior popliteal cyst aspiration followed by corticosteroid injection and those who received a subsequent anterior knee joint corticosteroid injection. This discovery has implications for the percutaneous treatment of patients with popliteal cyst and knee pain because it suggests that posterior cyst aspiration followed by a direct steroid injection into the Baker's cyst is a reasonable approach, rather than performing a separate anterior access for intra-articular knee injection.

Publication History

Article published online:
26 May 2023