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Cystic Lesions About the Knee Workup

  • Author: David M Gonzalez, MD, FACS; Chief Editor: Thomas M DeBerardino, MD  more...
Updated: Nov 03, 2015

Laboratory Studies

Laboratory studies are dictated by the patient's general condition. If infection is suggested, record vital signs and obtain a complete blood count (CBC) with differential and an erythrocyte sedimentation rate. Any possible undiagnosed medical condition should be investigated using appropriate laboratory and radiographic studies.


Imaging Studies

Obtain plain radiographs, and consider sonograms or any other studies as indicated. MRI is especially useful when evaluating knee cysts.[14, 15, 10, 16] See Baker Cyst Imaging.

MRIs may have to include intravenous contrast enhancement because high signal intensity on T2-weighted images does not necessarily mean that a structure is fluid filled.

Necrotic tissue, nerve sheath or myxoid tissue, flowing blood, and pus can all resemble cysts on T2-weighted MRIs.[17] Ultrasonography can also be used to determine if the mass is fluid filled.

Authors of a retrospective study regarding the prevalence of Baker cysts in patients with knee pain recommended that an ultrasound exam of the knee be performed in patients with painful osteoarthritis or evidence of effusion. They assessed the correlation between BC and severity of osteophytes and joint effusion and found that Baker cysts were present in 25.8% (102 of 399) of patients who had ultrasound features of osteoarthritis and joint effusion.


Computed tomography scanning, knee arthrography, tomography, and bone scanning have also been used.


Other Tests

Aspiration of the cystic mass can be useful in some situations, although recurrence of the cyst is common. Bursal cysts that occur secondary to trauma often respond to aspiration and injection of corticosteroids.


Histologic Findings

The cysts are lined with an epithelium. Bursal sacs are lined with a membrane similar to synovium. A Baker cyst is the most common synovial cyst. Adventitial cysts do not have a true epithelial lining or synovial lining and usually have thickened walls. Many meniscal cysts have been shown to have a clear communication with the joint and appear to be lined with synovium.

Contributor Information and Disclosures

David M Gonzalez, MD, FACS Partner, Sports Medicine Surgery and General Orthopaedic Surgery, San Antonio Orthopaedic Group

David M Gonzalez, MD, FACS is a member of the following medical societies: American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, Texas Medical Association, Western Orthopaedic Association, Texas Orthopaedic Association, Society of Military Orthopaedic Surgeons

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Thomas M DeBerardino, MD Associate Professor, Department of Orthopedic Surgery, Consulting Surgeon, Sports Medicine, Arthroscopy and Reconstruction of the Knee, Hip and Shoulder, Team Physician, Orthopedic Consultant to UConn Department of Athletics, University of Connecticut Health Center

Thomas M DeBerardino, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Association, American Orthopaedic Society for Sports Medicine

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Arthrex, Inc.; Ivy Sports Medicine; MTF; Aesculap; The Foundry, Cotera; ABMT<br/>Received research grant from: Histogenics; Cotera; Arthrex.

Additional Contributors

Robert D Bronstein, MD Associate Professor, Department of Orthopedics, Division of Athletic Medicine, University of Rochester School of Medicine

Robert D Bronstein, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, Medical Society of the State of New York

Disclosure: Nothing to disclose.

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Popliteal cyst. Courtesy of James K. DeOrio, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD.
Ganglion in the Hoffa fat pad. Courtesy of James K. DeOrio, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD.
Ganglion of the anterior cruciate ligament. Courtesy of James K. DeOrio, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD.
Meniscal cyst. Courtesy of James K. DeOrio, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD.
Tibial subchondral cyst. Courtesy of James K. DeOrio, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD.
Baker cyst. Sagittal T2-weighted magnetic resonance image shows a large Baker cyst (arrow) posteromedial to the joint capsule and adjacent to the medial gastrocnemius muscle. Note the joint effusion and underlying complex tear of the medial meniscus (arrowhead). Courtesy of William B. Morrison, MD.
Meniscal cyst. Coronal T2-weighted magnetic resonance image shows a cyst (arrow) adjacent to the lateral meniscus (arrowhead) and also demonstrates a tear communicating with the cyst. Courtesy of William B. Morrison, MD.
Prepatellar bursitis. Sagittal T2-weighted magnetic resonance image shows a fluid collection (arrow) anterior to the patella. Courtesy of William B. Morrison, MD.
Cruciate ganglion. Sagittal T2-weighted magnetic resonance image shows a cyst (arrow) that slightly displaces the otherwise normal-appearing anterior cruciate ligament. Courtesy of William B. Morrison, MD.
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