"The Importance of Adding Fenestration to Ultrasound-Guided Baker's Cyst Aspiration"

Overview

This study aims to evaluate whether adding a fenestration procedure to standard ultrasound-guided aspiration and corticosteroid-lidocaine injection provides additional clinical benefits for patients with symptomatic Baker's cyst associated with knee osteoarthritis. Baker's cyst is a fluid-filled swelling located behind the knee that may cause pain, stiffness, swelling, and limited mobility. Although aspiration with medication injection is commonly used to relieve symptoms, recurrence of the cyst is frequent. Fenestration is a minimally invasive technique in which small controlled openings are created in the cyst wall under ultrasound guidance to improve internal drainage and potentially reduce recurrence. In this prospective, randomized, double-blind, controlled study, participants will be assigned to one of two groups: 1. aspiration with corticosteroid and lidocaine injection, or 2. aspiration with corticosteroid and lidocaine injection plus fenestration. Pain, functional scores, cyst measurements, and recurrence will be assessed at follow-up visits at 2 weeks, 1 month, and 3 months. The purpose of this study is to determine whether the addition of fenestration results in better symptom improvement and lower rates of recurrence compared with standard aspiration alone.

Detailed description

Baker's cyst, also known as a popliteal cyst, is frequently observed in patients with knee osteoarthritis and is typically associated with intra-articular pathology that increases synovial fluid production. Ultrasound-guided aspiration combined with corticosteroid-lidocaine injection is a widely used minimally invasive treatment; however, recurrence remains a significant limitation of this method.

Fenestration involves creating multiple small perforations in the cyst wall using a needle under real-time ultrasound guidance. This technique is expected to enhance communication between the cyst and surrounding tissues, promote better fluid redistribution, and reduce the likelihood of reaccumulation.

This prospective, randomized, double-blind, controlled clinical trial will enroll adult patients meeting the 2010 ACR criteria for knee osteoarthritis and demonstrating a symptomatic Baker's cyst on ultrasound. Participants will be randomized in a 1:1 ratio into two groups:

Group 1: aspiration + corticosteroid-lidocaine injection

Group 2: aspiration + corticosteroid-lidocaine injection + fenestration

All procedures will be performed by a trained physiatrist using sterile technique and real-time ultrasonography. Outcome measures include VAS pain scores, KOOS, WOMAC, Rauschning-Lindgren classification, ultrasonographic cyst dimensions, and aspirated fluid volume. Assessments will be conducted at baseline and at 2-week, 1-month, and 3-month follow-up visits.

The primary objective is to investigate whether fenestration, when added to aspiration, enhances clinical outcomes and reduces recurrence rates. Secondary objectives include evaluating functional improvements, changes in cyst size, and patient-reported symptoms. The study duration for each participant is 3 months, and the overall study is planned to be completed within 5 months.

Interventions

• Procedure Baker's Cyst Aspiration
  With the patient in the prone position, the ultrasound probe is placed transversely over the gastrocnemius-semimembranosus bursa. Under real-time ultrasound guidance, the needle is advanced while visualizing neurovascular structures to avoid injury. Aspiration of the cyst content is performed in all participants.
• Drug Steroid-Lidocaine Injection
  Following aspiration, an injection mixture consisting of 1 mL betamethasone, 1 mL of 2% lidocaine, and 1 mL of 0.9% isotonic sodium chloride is administered into the decompressed cyst cavity under ultrasound guidance.
• Procedure Ultrasound-Guided Fenestration
  After aspiration, fenestration of the cyst wall is performed under ultrasound guidance. The cyst wall is punctured at a minimum of six different points using a needle to create communication with surrounding tissues and reduce recurrence. Following fenestration, the same steroid and local anesthetic mixture is administered.

Primary outcome measures

• Change in Baker's Cyst Volume [Time frame: Baseline, 2 weeks, 1 month, and 3 months after the intervention]

Secondary outcome measures (9)

• Change in Pain Severity (NRS Score) [Time frame: Baseline, 1 hour post-procedure, 2 weeks, 1 month, 3 months.]
• Change in Rauschning-Lindgren Classification (RLC) [Time frame: Baseline, 2 weeks, 1 month, 3 months.]
• Change in Knee Injury and Osteoarthritis Outcome Score (KOOS) [Time frame: Baseline, 2 weeks, 1 month, 3 months.]
• Change in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [Time frame: Baseline, 2 weeks, 1 month, 3 months.]
• Baseline OMERACT Ultrasound Score [Time frame: Baseline]
• Change in Kellgren-Lawrence (K-L) Grade [Time frame: Baseline only]
• Change in Cyst Characteristics on Ultrasound [Time frame: Baseline, 2 weeks, 1 month, 3 months.]
• Aspirated Fluid Volume [Time frame: During the procedure (single time point).]
• Change in Ultrasound Effusion Grade (OMERACT) [Time frame: Baseline, 2 weeks, 1 month, and 3 months]

Eligibility criteria

Inclusion criteria

• Adults aged 40 to 75 years
• Diagnosis of knee osteoarthritis according to the 2010 American College of Rheumatology (ACR) criteria
• Presence of a symptomatic Baker's cyst confirmed by ultrasonography
• Ability to understand study procedures and provide written informed consent
• Sufficient intellectual and social capacity to comply with study visits and follow-up requirements

Exclusion criteria

• Presence of inflammatory arthritis, septic arthritis, crystal arthropathy, or secondary causes of knee osteoarthritis
• Kellgren-Lawrence grade 4 knee osteoarthritis
• Active systemic infection
• History of malignancy
• Intra-articular knee injection within the past 3 months
• Knee trauma within the past 3 months
• History of knee surgery
• Contraindications to aspiration or corticosteroid injection (e.g., local infection, bleeding disorders, uncontrolled diabetes mellitus)
• Requirement to continue medications for inflammatory arthritis
• Diagnosed psychiatric disorder that may impair study participation
• Use of nonsteroidal anti-inflammatory drugs (NSAIDs) within the past 1 week
• Physical therapy applied to the knee region within the past 1 month

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Triple blind

Primary purpose

Treatment

Study locations

Turkey (Türkiye) · 1 center

• Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Physical Med — Istanbul

Publications

• Kim JM, Kang S, Yoon JS. Association of complicated Baker's cysts with knee pathologies as compared to simple Baker's cysts. Medicine (Baltimore). 2024 Jun 7;103(23):e38407. doi: 10.1097/MD.0000000000038407. PMID 38847688
• Mortada M, Amer YA, Zaghlol RS. Efficacy and Safety of Musculoskeletal Ultrasound Guided Aspiration and Intra-Lesional Corticosteroids Injection of Ruptured Baker's Cyst: A Retrospective Observational Study. Clin Med Insights Arthritis Musculoskelet Disord. 2020 Nov 10;13:1179544120967383. doi: 10.1177/1179544120967383. eCollection 2020. PMID 33223862
• Collins NJ, Misra D, Felson DT, Crossley KM, Roos EM. Measures of knee function: International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Injury and Osteoarthritis Outcome Score Physical Function Short Form (KOOS-PS), Knee Outcome Survey Activities of Daily Living Scale (KOS-ADL), Lysholm Knee Scoring Scale, Oxford PMID 22588746
• Ferdousi A, Islam MA, Begum M, Debnath MR, Shapla SP, Saha T, Biswas R, Ferdouse F, Rahman MA. Diagnostic Value of Ultrasonography in Determination of Knee Joint Pathologies with Comparison to MRI. Mymensingh Med J. 2024 Oct;33(4):989-995. PMID 39351715
• Bandinelli F, Fedi R, Generini S, Porta F, Candelieri A, Mannoni A, Innocenti M, Matucci Cerinic M. Longitudinal ultrasound and clinical follow-up of Baker's cysts injection with steroids in knee osteoarthritis. Clin Rheumatol. 2012 Apr;31(4):727-31. doi: 10.1007/s10067-011-1909-9. Epub 2011 Dec 27. PMID 22200813
• Chen CK, Lew HL, Liao RI. Ultrasound-guided diagnosis and aspiration of Baker's cyst. Am J Phys Med Rehabil. 2012 Nov;91(11):1002-4. doi: 10.1097/PHM.0b013e318269d95b. No abstract available. PMID 22955026
• Oo WM, Linklater JM, Bennell KL, Pryke D, Yu S, Fu K, Wang X, Duong V, Hunter DJ. Are OMERACT Knee Osteoarthritis Ultrasound Scores Associated With Pain Severity, Other Symptoms, and Radiographic and Magnetic Resonance Imaging Findings? J Rheumatol. 2021 Feb;48(2):270-278. doi: 10.3899/jrheum.191291. Epub 2020 May 15. PMID 32414954
• Acebes JC, Sanchez-Pernaute O, Diaz-Oca A, Herrero-Beaumont G. Ultrasonographic assessment of Baker's cysts after intra-articular corticosteroid injection in knee osteoarthritis. J Clin Ultrasound. 2006 Mar-Apr;34(3):113-7. doi: 10.1002/jcu.20210. PMID 16547992

Identifiers

NCT: NCT07385560 · E-24687290-604.01-1407310 · E-24687290-604.01-1407310

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗