Radiography
Findings
Imaging evaluation of a popliteal mass begins with conventional radiography to detect a soft-tissue mass, calcifications, and bony involvement. A Baker cyst appears as a soft-tissue mass in the posteromedial knee joint (see Image below and Image 2 in Multimedia).
Anteroposterior radiograph of the knee shows uniform joint-space loss in the medial and lateral knee compartments without osteophytosis. A Baker cyst is seen medially (arrowhead).
Occasionally, a Baker cyst is suggested by the presence of multiple, calcified, loose bodies in the cyst (see Images below and Image 8, Image 9 in Multimedia).
Anteroposterior radiograph of the knee shows calcifications (arrowhead) overlying the medial tibial plateau.
Lateral radiograph of the knee shows multiple calcified bodies (arrowhead) posterior to the knee, which is consistent with synovial osteochondromatosis.
Rarely, a solitary loose body in a Baker cyst may mimic a fabella on a lateral radiograph of the knee (see Image below and Image 10 in Multimedia).
Lateral radiograph of the knee shows a calcified body (arrowhead), which appears to be a large fabella, posterior to the knee.
However, on frontal radiograph (see Image below and Image 11 in Multimedia), the calcified body in the Baker cyst will be located behind the medial femoral condyle, whereas a fabella will be present behind the lateral femoral condyle.
Anteroposterior radiograph of the knee shows that a calcified body (arrowhead) is overlying the medial femoral condyle, making a fabella highly unlikely. The calcified, loose body is in a Baker cyst.
Computed Tomography
Contrast-enhanced, axial computed tomography (CT) scan of the knee shows multiple gaslike lucencies within a Baker cyst and synovial enhancement.
Findings
On a CT scan, a Baker cyst appears as a fluid-containing mass located behind the medial femoral condyle and between the tendons of the medial head of the gastrocnemius and semimembranosus muscles. A space-occupying lesion in the posteromedial knee suggests the diagnosis but is not always sufficient to exclude other etiologies, for which MRI or ultrasonography is more specific.
Degree of Confidence
CT scanning is not as sensitive as MRI in detecting an internal derangement, which may be the cause of a Baker cyst. In addition, the definitive diagnosis of a Baker cyst may not be made without the injection of air and/or iodinated contrast material into the knee joint.
Magnetic Resonance Imaging
Findings
On MRI, a Baker cyst appears as a homogeneous, high – signal intensity, cystic mass behind the medial femoral condyle; a thin, fluid-filled neck interdigitates between the tendons of the medial head of the gastrocnemius and semimembranosus muscles (see Image below and Image 7 in Multimedia).22
Axial, T2-weighted magnetic resonance image with fat saturation reveals a Baker cyst connected to the knee joint by way of a narrow neck between the tendons of the medial head of the gastrocnemius and semimembranosus muscles.
An uncomplicated Baker cyst should demonstrate homogeneous high signal intensity on all fluid-sensitive pulse sequences, including on the second echo of a conventional or fast/turbo spin-echo sequence, on short tau inversion recovery (STIR), or on gradient echo (GRE)/fast field echo (FFE) sequences employing a low flip angle (10-30 º). The axial plane (see Image above and Image 7 in Multimedia) allows the cyst, neck, and joint space to be seen in contiguity, although the cyst may be demonstrated in all 3 planes.
In addition, intravenously administered gadolinium can detect synovial enhancement (see Images below and Image 12, Image 13 in Multimedia) and pannus formation in RA in the cyst and in the joint space proper, prior to the radiographic detection of well-known signs of RA much later in the course of the disease (erosion, uniform joint space loss without marked osteophytosis, periarticular osteopenia, soft-tissue swelling).
Axial, T2-weighted magnetic resonance image of the knee shows effusion, synovial proliferation (white arrowhead), and a Baker cyst that contains debris (black arrowhead).
Axial, T1-weighted magnetic resonance image of the knee after the intravenous administration of gadolinium shows synovial enhancement (arrowhead).
Off-label usage of intra-articular gadolinium in magnetic resonance arthrography, now common in establishing the presence of a meniscal retear, is perhaps the most vivid way to display a Baker cyst. MRI also can detect underlying internal derangements of the knee (see Images below and Image 14, Image 15 in Multimedia), which may be etiologic in the formation of a Baker cyst.
Sagittal, T2-weighted magnetic resonance image with fat saturation of the knee shows a large knee effusion and a Baker cyst.
Sagittal, T2-weighted magnetic resonance image with fat saturation of the knee, lateral to the view in Image above, shows a complete rupture of the anterior cruciate ligament.
In a complex Baker cyst, calcified, loose bodies can be detected; these appear on fluid-sensitive images as low – signal intensity, rounded foci within high – signal intensity, cystic fluid (see Images below and Image 17, Image 18 in Multimedia) .
Sagittal, T2-weighted magnetic resonance image shows a Baker cyst containing hypointense, loose bodies.
Axial, T2-weighted magnetic resonance image with fat saturation shows a Baker cyst containing hypointense, loose bodies.
Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography (MRA) scans.
NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
Ultrasonography
Findings
Ultrasonography is a very helpful imaging technique in the evaluation of a popliteal mass.23,24,25 The modality can be used to determine whether the popliteal mass is a cyst or a solid mass. A simple Baker cyst appears as an anechoic mass with posterior acoustic enhancement that communicates with the knee joint. Findings on an ultrasonogram relate to the criteria of a simple cyst, which include an anechoic mass, a sharply defined posterior wall, and posterior acoustic enhancement. A complex Baker cyst has internal echoes within the hypoechoic mass (see Images below and Image 3, Image 4 in Multimedia). Calcified, loose bodies within a Baker cyst appear as mobile, intraluminal, echogenic foci with distal acoustic shadowing, an appearance similar to that of cholelithiasis in a gallbladder. An additional advantage of ultrasonography is that it can exclude a coexisting DVT.
Transverse ultrasonographic image of the knee in a patient who had recent arthroscopy shows a complex, cystic mass (arrow) in the medial aspect of popliteal fossa. The mass communicates with the knee joint (arrowhead), which is consistent with a Baker cyst.
Longitudinal ultrasonographic image of a Baker cyst in a patient who underwent recent knee arthroscopy.
Color Doppler ultrasonography can detect vascular flow within the mass to exclude a popliteal artery aneurysm. In cystic adventitial degeneration of the popliteal artery, ultrasonographic examination reveals multiple cystic structures surrounding a normal-sized artery (see Images below and Image 5, Image 6 in Multimedia).
Transverse ultrasonographic image of the popliteal fossa shows a complex, cystic mass (arrowhead).
Transverse color Doppler ultrasonographic image of the popliteal fossa shows multiple cysts surrounding a normal-sized popliteal artery (A), which is consistent with cystic adventitial degeneration.
Degree of Confidence
This is the fastest, most cost-effective manner in which to diagnose a Baker cyst.
False Positives/Negatives
A cyst that is too large or complex may obscure visualization of the fluid-filled connection to the joint space proper, leading to a false-positive diagnosis.
More on Baker Cyst |
| Overview: Baker Cyst |
 Imaging: Baker Cyst |
| Follow-up: Baker Cyst |
| Multimedia: Baker Cyst |
| References |
| Further Reading |
| « Previous Page | Next Page » |
References
Baker WM. On the formation of synovial cysts in the leg in connection with disease of the knee-joint. 1877. Clin Orthop Relat Res. Feb 1994;(299):2-10. [Medline].
Pinnamaneni S, Thomas PS. Anatomy, imaging, treatment options for Baker's Cyst. Pain Physician. May-Jun 2008;11(3):376-7; author reply 377-8. [Medline].
Corten K, Vandenneucker H, Reynders P, Nijs S, Pittevils T, Bellemans J. A pyogenic, ruptured Baker's cyst induced by arthroscopic pressure pump irrigation. Knee Surg Sports Traumatol Arthrosc. Dec 16 2008;[Medline].
Fritschy D, Fasel J, Imbert JC, et al. The popliteal cyst. Knee Surg Sports Traumatol Arthrosc. Jul 2006;14(7):623-8. [Medline].
Jayson MI, Dixon AS. Valvular mechanisms in juxta-articular cysts. Ann Rheum Dis. Jul 1970;29(4):415-20. [Medline]. [Full Text].
Rauschning W, Lindgren PG. The clinical significance of the valve mechanism in communicating popliteal cysts. Arch Orthop Trauma Surg. 1979;95(4):251-6. [Medline].
Bryan RS, DiMichele JD, Ford GL Jr. Popliteal cysts. Arthrography as an aid to diagnosis and treatment. Clin Orthop Relat Res. Jan-Feb 1967;50:203-8. [Medline].
Chatzopoulos D, Moralidis E, Markou P, Makris V, Arsos G. Baker's cysts in knees with chronic osteoarthritic pain: a clinical, ultrasonographic, radiographic and scintigraphic evaluation. Rheumatol Int. Dec 2008;29(2):141-6. [Medline].
Fam AG, Wilson SR, Holmberg S. Ultrasound evaluation of popliteal cysts on osteoarthritis of the knee. J Rheumatol. May-Jun 1982;9(3):428-34. [Medline].
Andonopoulos AP, Yarmenitis S, Sfountouris H, et al. Baker's cyst in rheumatoid arthritis: an ultrasonographic study with a high resolution technique. Clin Exp Rheumatol. Sep-Oct 1995;13(5):633-6. [Medline].
Szer IS, Klein-Gitelman M, DeNardo BA. Ultrasonography in the study of prevalence and clinical evolution of popliteal cysts in children with knee effusions. J Rheumatol. Mar 1992;19(3):458-62. [Medline].
Guerra J Jr, Newell JD, Resnick D. Pictorial essay: gastrocnemio-semimembranosus bursal region of the knee. AJR Am J Roentgenol. Mar 1981;136(3):593-6. [Medline]. [Full Text].
Johnson LL, van Dyk GE, Johnson CA, et al. The popliteal bursa (Baker's cyst): an arthroscopic perspective and the epidemiology. Arthroscopy. Feb 1997;13(1):66-72. [Medline].
Fielding JR, Franklin PD, Kustan J. Popliteal cysts: a reassessment using magnetic resonance imaging. Skeletal Radiol. 1991;20(6):433-5. [Medline].
Stone KR, Stoller D, De Carli A, et al. The frequency of Baker's cysts associated with meniscal tears. Am J Sports Med. Sep-Oct 1996;24(5):670-1. [Medline].
Miller TT, Staron RB, Koenigsberg T. MR imaging of Baker cysts: association with internal derangement, effusion, and degenerative arthropathy. Radiology. Oct 1996;201(1):247-50. [Medline]. [Full Text].
Sansone V, de Ponti A, Paluello GM. Popliteal cysts and associated disorders of the knee. Critical review with MR imaging. Int Orthop. 1995;19(5):275-9. [Medline].
Ahn JH, Yoo JC, Lee SH, et al. Arthroscopic cystectomy for popliteal cysts through the posteromedial cystic portal. Arthroscopy. May 2007;23(5):559.e1-4. [Medline].
Linetsky F. Sclerotherapy for Baker's Cyst. Pain Physician. May-Jun 2008;11(3):375-6. [Medline].
Centeno CJ, Schultz J, Freeman M. Sclerotherapy of Baker's cyst with imaging confirmation of resolution. Pain Physician. Mar-Apr 2008;11(2):257-61. [Medline].
Taurino M, Rizzo L, Stella N, Mastroddi M, Conteduca F, Maggiore C, et al. Doppler ultrasonography and exercise testing in diagnosing a popliteal artery adventitial cyst. Cardiovasc Ultrasound. May 27 2009;7:23. [Medline].
Marra MD, Crema MD, Chung M, Roemer FW, Hunter DJ, Zaim S, et al. MRI features of cystic lesions around the knee. Knee. Dec 2008;15(6):423-38. [Medline].
Acebes JC, Sánchez-Pernaute O, Díaz-Oca A, et al. Ultrasonographic assessment of Baker's cysts after intra-articular corticosteroid injection in knee osteoarthritis. J Clin Ultrasound. Mar-Apr 2006;34(3):113-7. [Medline].
Barisic I, Ljutic D, Vlak T, et al. Laboratory and sonographic findings in dialyzed patients with bilateral chronic knee pain versus dialyzed asymptomatic patients. Coll Antropol. Jun 2007;31(2):489-94. [Medline].
Gompels BM, Darlington LG. Grey scale ultrasonography and arthrography in evaluation of popliteal cysts. Clin Radiol. Sep 1979;30(5):539-45. [Medline].
Corten K, Vandenneucker H, Reynders P, Nijs S, Pittevils T, Bellemans J. A pyogenic, ruptured Baker's cyst induced by arthroscopic pressure pump irrigation. Knee Surg Sports Traumatol Arthrosc. Mar 2009;17(3):266-9. [Medline].
Anderson CJ, Cannon GW, Andrews JM. Gouty tophus presenting as "pseudo-Baker's cyst". J Rheumatol. Sep 1989;16(9):1281-2. [Medline].
Chaudhuri R, Salari R. Baker's cyst simulating deep vein thrombosis. Clin Radiol. Jun 1990;41(6):400-4. [Medline].
Cuende E, Barbadillo C, E-Mazzucchelli R. Candida arthritis in adult patients who are not intravenous drug addicts: report of three cases and review of the literature. Semin Arthritis Rheum. Feb 1993;22(4):224-41. [Medline].
De Greef I, Molenaers G, Fabry G. Popliteal cysts in children: a retrospective study of 62 cases. Acta Orthop Belg. Jun 1998;64(2):180-3. [Medline].
De Maeseneer M, Debaere C, Desprechins B. Popliteal cysts in children: prevalence, appearance and associated findings at MR imaging. Pediatr Radiol. Aug 1999;29(8):605-9. [Medline].
Dunlop D, Parker PJ, Keating JF. Ruptured Baker's cyst causing posterior compartment syndrome. Injury. Oct 1997;28(8):561-2. [Medline].
Fergusson C, Burge P. An unusual loose body in the knee. Clin Orthop Relat Res. May 1986;(206):233-5. [Medline].
Goldberg RP, Genant HK. Calcified bodies in popliteal cysts: a characteristic radiographic appearance. AJR Am J Roentgenol. Nov 1978;131(5):857-9. [Medline].
Gompels BM, Darlington LG. Evaluation of popliteal cysts and painful calves with ultrasonography: comparison with arthrography. Ann Rheum Dis. Aug 1982;41(4):355-9. [Medline]. [Full Text].
Ha TV, Kleinman PK, Fraire A. MR imaging of benign fatty tumors in children: report of four cases and review of the literature. Skeletal Radiol. Jul 1994;23(5):361-7. [Medline].
Hammoudeh M, Siam AR, Khanjar I. Anterior dissection of popliteal cyst causing anterior compartment syndrome. J Rheumatol. Jul 1995;22(7):1377-9. [Medline].
Houston CS. Pitfalls to avoid. When is a fabella not a fabella?. J Can Assoc Radiol. Sep 1978;29(3):193. [Medline].
Kattapuram SV. Case report 181: calcified popliteal cyst (Baker cyst). Skeletal Radiol. Jan 1982;7(4):279-81. [Medline].
Krome J, de Araujo W, Webb LX. Acute compartment syndrome in ruptured Baker's cyst. J South Orthop Assoc. 1997;6(2):110-4. [Medline].
Langsfeld M, Matteson B, Johnson W, et al. Baker's cysts mimicking the symptoms of deep vein thrombosis: diagnosis with venous duplex scanning. J Vasc Surg. Apr 1997;25(4):658-62. [Medline].
Lepore L, Rabusin M, Pennesi M, et al. Bilateral Baker's cyst in a patient with psoriatic arthritis of pediatric onset. Clin Exp Rheumatol. Jan-Feb 1996;14(1):109-10. [Medline].
Mangiafico RA, Santonocito M, Mandalà ML, et al. [Pseudothrombophlebitis due to an expansive popliteal cyst associated with Reiter's syndrome]. Minerva Med. Sep 1995;86(9):391-4. [Medline].
Marques Filho J. [Pseudothrombophlebitis syndrome in Reiter's syndrome]. Rev Assoc Med Bras. May-Jun 1995;41(3):252-4. [Medline].
McLeod BC, Charters JR, Straus AK. Gas-like radiolucencies in a popliteal cyst. Rheumatol Int. 1983;3(3):143-4. [Medline].
Molpus WM, Shah HR, Nicholas RW, et al. Case report 731. Complicated Baker's cyst. Skeletal Radiol. 1992;21(4):266-8. [Medline].
Munk PL, Vellet AD, Levin MF. Leaking Baker's cyst detected by magnetic resonance imaging. Can Assoc Radiol J. Apr 1993;44(2):125-8. [Medline].
Onetti CM, Gutiérrez E, Hliba E, et al. Synoviorthesis with 32P-colloidal chromic phosphate in rheumatoid arthritis--clinical, histopathologic and arthrographic changes. J Rheumatol. Mar-Apr 1982;9(2):229-38. [Medline].
Petros DP, Hanley JF, Gilbreath P, et al. Posterior compartment syndrome following ruptured Baker's cyst. Ann Rheum Dis. Nov 1990;49(11):944-5. [Medline]. [Full Text].
Reilly PA, Maddison PJ. Painful, swollen calf in a patient with SLE. Br J Rheumatol. Aug 1987;26(4):319-20. [Medline].
Rennebohm RM, Towbin RB, Crowe WE. Popliteal cysts in juvenile rheumatoid arthritis. AJR Am J Roentgenol. Jan 1983;140(1):123-5. [Medline]. [Full Text].
Rubin BR, Gupta VP, Levy RS. Anaerobic abscess of a popliteal cyst in a patient with rheumatoid arthritis. J Rheumatol. Sep-Oct 1982;9(5):733-4. [Medline].
Schultz E, Rosenblatt R, Mitsudo S. Detection of a deep lipoblastoma by MRI and ultrasound. Pediatr Radiol. 1993;23(5):409-10. [Medline].
Scott WN, Jacobs B, Lockshin MD. Posterior compartment syndrome resulting from a dissecting popliteal cyst. Case report. Clin Orthop Relat Res. Jan-Feb 1977;(122):189-92. [Medline].
Seil R, Rupp S, Jochum P. Prevalence of popliteal cysts in children. A sonographic study and review of the literature. Arch Orthop Trauma Surg. 1999;119(1-2):73-5. [Medline].
Siegel HJ, Luck JV Jr, Siegel ME. Hemarthrosis and synovitis associated with hemophilia: clinical use of P-32 chromic phosphate synoviorthesis for treatment. Radiology. Jan 1994;190(1):257-61. [Medline]. [Full Text].
Simpson FG, Robinson PJ, Bark M. Prospective study of thrombophlebitis and "pseudothrombophlebitis". Lancet. Feb 16 1980;1(8164):331-3. [Medline].
Sung MS, Kang HS, Suh JS. Myxoid liposarcoma: appearance at MR imaging with histologic correlation. Radiographics. Jul-Aug 2000;20(4):1007-19. [Medline]. [Full Text].
Takano Y, Oida K, Kohri Y, et al. Is Baker's cyst a risk factor for pulmonary embolism?. Intern Med. Nov 1996;35(11):886-9. [Medline]. [Full Text].
Toolanen G, Lorentzon R, Friberg S. Sonography of popliteal masses. Acta Orthop Scand. Jun 1988;59(3):294-6. [Medline].
Volteas SK, Labropoulos N, Leon M, et al. Incidence of ruptured Baker's cyst among patients with symptoms of deep vein thrombosis. Br J Surg. Mar 1997;84(3):342. [Medline].
Wallner RJ, Dadparvar S, Croll MN, et al. Demonstration of an infected popliteal (Baker's) cyst with three-phase skeletal scintigraphy. Clin Nucl Med. Mar 1985;10(3):153-5. [Medline].
Wilson AJ, Ford LT, Gilula LA. Migrating mouse: a sign of dissecting popliteal cyst. AJR Am J Roentgenol. Apr 1988;150(4):867-8. [Medline]. [Full Text].
Further Reading
Related eMedicine topics
Osteoarthritis
Neuropathic Arthropathy (Charcot Joint)
Arthrocentesis, Knee
The Approach to the Painful Joint
Patellofemoral Joint Syndromes
Cystic Lesions About the Knee
Knee Injury, Soft Tissue
Clinical guideline
Ultrasonographic examinations: indications and preparation of the patient.
Finnish Medical Society Duodecim - Professional Association. 2000 Apr 18 (revised 2007 Jan 11). Various pagings. NGC:005501
Keywords
Baker cyst, Baker's cyst, popliteal cyst, popliteal bursa, gastrocnemio-semimembranosus bursa, gastrocnemio-semimembranous bursa, gastrocnemiosemimembranosus bursa, gastrocnemiosemimembranous bursa
