Sonomorphologic variants of popliteal cysts

Association of complicated Baker's cysts with knee pathologies as compared to simple Baker's cysts

Baker's cysts (BCs) are known to be associated with intra-articular pathologies. BCs can be classified into 2 types: simple and complicated. Although some studies have focused on BC using magnetic resonance imaging (MRI), which is the gold standard examination, no study has compared knee MRI features in patients with simple and complicated BCs. To assess the relationship between the type of BC (simple vs complicated) and other knee pathologies using MRI. Seventy patients who underwent knee MRI examination due to symptomatic knee were retrospectively recruited from April 2011 to April 2021 at a single hospital. In the knee MRI images, the following were assessed: type (simple or complicated), morphology, volume of BCs, thickness of the suprapatellar recess, presence of synovial proliferation of the suprapatellar recess, grade of knee joint effusion, presence of meniscal tear, and extent of meniscal extrusion. The patients were classified into 2 groups according to the type of BC: simple BC and complicated BC. The differences between the 2 groups were evaluated for all variables. Finally, 52 patients were included in this study, 15 were classified as "simple BC" group and 37 as "complicated BC" group. The volume of complicated BC (median: 4.6, interquartile range - IQR: 1.6-12.4) was significantly greater than that of simple BC (median: 0.7, IQR: 0.3-3.7; P = .007). The presence of synovial proliferation in the suprapatellar recess was significantly higher in complicated BC (91.9%) than that in simple BC (46.7%; P = .001). The thickness of the suprapatellar recess was significantly greater in complicated BC (median: 7.5, IQR: 5.8-10.7) than that in simple BC (median: 4.3, IQR: 2.3-7.6; P = .020). The medial meniscus extrusion was greater in complicated BC (median: 4.1, IQR: 2.8-5.1) than that in simple BC (median: 2.5, IQR: 1.8-4.4; P = .037). After adjusting these P-values using the Holm method, only the presence of synovial proliferation in the suprapatellar recess remained significant (P = .010). Using knee MRI images, we demonstrated that complicated BCs are more associated with intra-articular pathologies than simple BCs; such as cyst volume, amount of the knee joint effusion, synovial proliferation and medial meniscal extrusion. Among them, the presence of synovial proliferation was the most significant factor associated with complicated BCs.

Clinical, Radiographic, and Ultrasound Findings Between Simple and Complicated Baker's Cysts

PURPOSE

The aim of the study was to compare the clinical, radiographic, and ultrasound findings between simple and complicated Baker's cysts.

METHODS

Forty-seven knees with Baker's cysts in 45 patients with knee pain were identified from a chart review. Baker's cysts were classified as simple or complicated according to ultrasound findings. Clinical data, including duration of knee pain, visual analog scale score, Kellgren-Lawrence grade, ultrasound findings, including the size and sonomorphology of the BC, severity of osteophytosis, thickness of joint effusion, meniscal tear, and synovial proliferation of the two types of BC, were compared.

RESULTS

There were 22 knees with a simple cyst and 25 knees with a complicated cyst. The thickness of the suprapatellar effusion in complicated Baker's cysts (5.7 ± 3.0 mm) was significantly greater than that in simple Baker's cysts (3.8 ± 3.2 mm), and the presence of synovial proliferation in the suprapatellar recess was significantly higher in complicated Baker's cysts (22 knees, 88.0%) than in the simple Baker's cysts (12 knees, 54.5%). However, there were no significant differences in demographic, radiographic, and other ultrasound parameters between the two types of BC.

CONCLUSIONS

Synovial proliferation with larger effusion in the suprapatellar recess was more associated with complicated BC than simple BC.

The Sonographic Spectrum of Baker Cysts

Baker cysts are the most common pathologic finding in the sonography of the popliteal fossa. They have a wide range of sonographic appearances. Some of them may need to be recognized and differentiated from other popliteal lesions. Therefore, familiarity with their different imaging appearances is useful for clinical practice. This review summarized different presentations of Baker cysts. They are described in several categories, organized according to their shape and formation: typical Baker cysts and their mild variations, atypical small Baker cysts, ʎ-shaped Baker cysts and their related variations, Baker cysts with extension into nearby muscles, and Baker cysts with complications. The related differentiations are included in each category. The pathogenesis of Baker cysts is also discussed.

Popliteal cysts in paediatric patients: clinical characteristics and imaging features on ultrasound and MRI

Popliteal cysts, or Baker cysts, are considered rare in children and may exhibit particular features, as compared with adults. We studied data from 80 paediatric patients with 55 Baker cysts, examined over a period of 7 years, and correlated clinical presentation with findings on ultrasonography and MRI. Prevalence of popliteal cysts was 57% in arthritic knees, 58% with hypermobility syndrome, and 28% without risk factors. Only one patient had a trauma history and showed an ipsilateral cyst. Mean cyst volume was 3.4 mL; cysts were larger in boys. Patients with arthritis had echogenic cysts in 53%. Cyst communication with the joint space was seen in 64% on ultrasonography and 86% on MRI. In conclusion, Baker cysts are a common finding in a clinically preselected paediatric population. Children with Baker cysts should be assessed for underlying arthritis and inherited joint hypermobility, while sporadic Baker cysts appear to be common, as well.

Sonography of the knee joint()

The aim of this article is to review the sonographic appearances of common disorders involving the knee joint. Ultrasound is a sensitive method for diagnosis of tendon injuries. Injured ligaments appear swollen with mixed echogenicity. Meniscal injuries and muscle tears can be easily diagnosed. Ultrasound shows synovial thickening and effusion in inflammatory arthropathy and erosions of the articular surface in degenerative arthritis. It can be used effectively in the detection of rheumatoid arthritic activity and for grading degenerative arthritis lesions. Cystic lesions, as well as benign and malignant soft-tissue masses, are clearly delineated. Ultrasound is a safe noninvasive imaging modality that can be used for diagnosis of different disorders involving the knee joint.

Giant synovial cyst of knee treated arthroscopically through a cystic portal

Synovial cysts are well-defined fluid filled cysts that can extend for a variable distance outside the joint space. These cysts can sometimes grow to a large size making its treatment challenging especially when associated with intra-articular pathologies. We describe a case of giant synovial cyst arising from the left knee and extending to the medial proximal calf in a 77-year old female who presented with knee joint pain, episodes of locking and calf mass occurring within 2 months of onset. Imaging studies also showed associated medial and lateral meniscal tears with medial compartment and patellofemoral osteoarthritis. The cyst was treated by disrupting the valvular mechanism using a standard posteromedial portal and complete excision of the cyst wall via a posteromedial cystic portal. The meniscal lesions were dealt with through the standard anterior portals. At 25-month follow up there were no signs of recurrence of the cyst clinically or with MRI. The cystic portal technique is effective in treating a giant synovial cyst of the knee even in the presence of meniscal tears and high grade chondral lesions.

Ultrasonography of the lower extremity

Ultrasonography is a useful imaging tool for various soft tissue and joint pathologies affecting the lower extremity. This article reviews the normal sonographic appearance of muscles, tendons, ligaments, nerves, bone, and cartilage. The ultrasound imaging appearance of various pathologic conditions affecting the hip, thigh, knee, lower leg, ankle,and foot are illustrated. The advantages of ultrasonography are highlighted.

Uncommon synovial cysts in children

Popliteal synovial cysts (Baker's cysts) are a common occurrence in children and adults. Synovial cysts in other locations and/or with atypical extension are less common and may be confounded with tumors or other medical conditions. In this article we describe the underlying disease, clinical presentation and clinical course in six children with a sudden onset of paraarticular soft tissue masses or non-specific chronic pain. Ultrasound was the initial imaging method used in all cases; this was supplemented by MRI in three patients. Four children were diagnosed to be suffering from juvenile idiopathic arthritis (JIA), one child from Lyme Arthritis, whereas in one child no underlying disease was identified. Well-demarcated hypoechogenic lesions without signs of perfusion extending from the shoulder (two patients), elbow (one patient), hip (one patient), knee (1) or ankle (one patient) far into the adjacent musculature were detected on ultrasonography. A direct connection to the joint was demonstrated in all cases. All synovial cysts in the five arthritic patients resolved rapidly with medical treatment for arthritis, whereas the cyst persisted in the non-JIA patient.

CONCLUSION

Uncommon synovial cysts occur in particular as a complication of arthritis. Ultrasonography is the initial and follow-up imaging method of choice, which can be supplemented by MRI in unusual cases. Apart from treatment for arthritis, no specific therapeutic interventions were required in the present cases.

Prevalence and size of meniscal cysts, ganglionic cysts, synovial cysts of the popliteal space, fluid-filled bursae, and other fluid collections in asymptomatic knees on MR imaging

OBJECTIVE

The purposes of this study were to evaluate the prevalence and determine the size of meniscal cysts, ganglionic cysts, synovial cysts of the popliteal space, fluid-filled bursae, and other fluid collections on MR images of asymptomatic knees.

MATERIALS AND METHODS

MR images of 102 asymptomatic knees were evaluated with regard to the prevalence of meniscal cysts, ganglionic cysts, synovial cysts of the popliteal space, fluid-filled bursae, and other fluid collections. The MR examinations were performed in patients (mean age, 42.8 years; age range, 18-73 years) with clinically suspected meniscal lesions in the contralateral knee. The craniocaudal, anteroposterior, and mediolateral diameters of detectable abnormal fluid collections were measured.

RESULTS

Medial meniscal cysts (mean size [craniocaudal x anteroposterior x mediolateral], 9 x 6 x 13 mm) were found in four asymptomatic knees. Neither lateral meniscal cysts nor ganglionic cysts of the cruciate ligaments were identified. Twenty-six synovial cysts of the popliteal space (Baker's cyst)-consisting of 11 gastrocnemius portions (mean size, 19 x 8 x 10 mm) and 15 semimembranosus portions (mean size, 20 x 7 x 9 mm)-were found in 19 knees. Twenty-four (92%) of these cysts had a maximal diameter of 30 mm or less. Fluid-filled bursae were found in 49 knees. The deep infrapatellar bursa was most commonly involved (42 knees; mean size, 6 x 3 x 5 mm). Fluid-filled anserine bursae (mean size, 27 x 12 x 10 mm) were detected in five knees.

CONCLUSION

Meniscal cysts may be present in asymptomatic knees, at least on the medial side. Synovial cysts of the popliteal space can be found in approximately one fifth of asymptomatic knees. Their maximal diameter is usually smaller than 30 mm.

Imaging of soft-tissue myxoma with emphasis on CT and MR and comparison of radiologic and pathologic findings

PURPOSE

To determine the imaging characteristics of soft-tissue myxoma, with emphasis on computed tomographic (CT) and magnetic resonance (MR) imaging findings and pathologic comparison.

MATERIALS AND METHODS

Records of 45 pathologically confirmed soft-tissue myxomas in 44 patients were retrospectively reviewed. Patient demographics and radiographs (n = 20), bone scintigrams (n = 2), angiograms (n = 3), and ultrasonographic (US) (n = 6), CT (n = 14), and MR images (n = 33) were evaluated by two musculoskeletal radiologists with agreement by consensus for lesion location, lesion size, and intrinsic characteristics.

RESULTS

Soft-tissue myxoma more commonly affected women (59%; average age 52 years) and manifested as a slowly enlarging (64%) painful (51%) mass. Lesions were most frequently intramuscular (82%) and involved the thigh (51%). An appearance similar to that of a cyst was seen at CT (at which the lesions demonstrated low attenuation) and at MR imaging (at which the lesions demonstrated markedly high signal intensity on T2-weighted images) in all cases because of the high water content of mucin that was seen histologically. The true solid architecture of these lesions was best depicted in all cases at US (at which the lesions were hypoechoic, not anechoic) and on MR images obtained with contrast material (at which the lesions demonstrated internal enhancement). A small amount of tissue similar to fat surrounding these intramuscular myxomas (71% at MR imaging) corresponded histologically (70%) to atrophy of surrounding muscle.

CONCLUSION

Soft-tissue myxoma often demonstrates characteristic US, CT, and MR imaging findings, including intramuscular location, intrinsic high water content, and a surrounding rim of fat.

Popliteal cysts in adults. Prevalence, associated intraarticular lesions, and results after arthroscopic treatment

The objective of this prospective study was to determine the prevalence of popliteal cysts and the associated intraarticular lesions in a group of 100 patients scheduled for arthroscopic surgery of the knee and to evaluate the results of arthroscopic treatment for these intraarticular lesions without removal of the cyst. One hundred patients without any knee complaints served as a control group. The diagnosis of a popliteal cyst was made on the basis of ultrasonography. The prevalence of popliteal cysts was 20% in the study group and 0% in the control group. Patients with a popliteal cyst had a significantly higher prevalence of medial meniscal tears (70% versus 19%) and of chondral lesions (85% versus 28%). Tears of the lateral meniscus, however, were more evenly distributed (20% versus 36%). Sixteen of 20 patients with a popliteal cyst were available for a follow-up examination 1 to 3 years after the arthroscopic procedure. Eleven popliteal cysts had persisted. Chondral lesions were the most relevant prognostic factor; all patients with persisting cysts had grade III or grade IV lesions. We conclude that the popliteal cyst is a secondary phenomenon and that treatment should address the underlying intraarticular lesions. In cases of osteoarthritis it may be impossible to treat the chondral lesion successfully in terms of eliminating the effusion.

Popliteal cysts in adults: a review

OBJECTIVE

To review the epidemiology, clinical presentation, pathogenesis, imaging, differential diagnosis, complications, and treatment of popliteal cysts.

METHODS

References were taken from MEDLINE from 1985 to 1998 under the subject "Popliteal Cyst" with subheadings of Radiography, Ultrasonography, and Radionuclide Imaging. Other pertinent references were used. Childhood cysts were excluded.

RESULTS

Depending on the studied population and the imaging technique, 5% to 32% of knee problems may have these cysts, with 2 age-incidence peaks of 4 to 7 years and 35 to 70 years. In older patients there is usually coexistent joint pathology. Symptoms may arise in the popliteal fossa from the cyst itself or be dominated by knee pain from coexisting knee pathology. Many cysts are asymptomatic. Physical examination will miss one half of these cysts. Pathogenesis depends on the connection between the joint and bursa, with a valvelike effect allowing passage of fluid from the joint into the bursa with subsequent distention producing these cysts. Some bursae have no such joint-bursal communication, and the cysts arise primarily as bursitis of the gastrocnemio-semimembranosus bursa. Imaging is performed by plain x-ray, ultrasound, arthrography, computerized axial tomography, magnetic resonance imaging, or nuclear scan; sonography is the method of choice. Complicated cysts with extension or rupture into the calf mimic phlebitis, an important differential diagnosis. Asymptomatic cysts found incidentally need no treatment; most symptomatic cysts respond to intra-articular corticosteroid injections. Surgical excision is rarely necessary.

CONCLUSIONS AND RELEVANCE

Popliteal cysts are fairly common, may not be found on physical examination, require imaging (preferably sonography) to be identified, mimic phlebitis when extending into the calf, and often respond to intra-articular steroid or, rarely, surgical resection.

Sonographic detection of Baker's cysts: comparison with MR imaging

OBJECTIVE

The objective of this study was to assess the ability of sonography to reveal Baker's cysts using MR imaging as a gold standard.

MATERIALS AND METHODS

The study group consisted of 36 consecutive knees in 36 patients evaluated with both MR imaging and sonography. Inclusion criteria included axial proton density-weighted or T2-weighted MR images, a sonography report that documented the evaluation of the popliteal region of the knee, and sonographic and MR images that were available for review. The MR images were retrospectively reviewed for the presence of Baker's cyst (fluid signal between the semimembranosus and medial gastrocnemius tendons). Sonography reports were compared with the MR imaging results. The sonographic images were also retrospectively reviewed to determine whether any characteristic findings on sonography were significantly associated with the presence of Baker's cyst on MR imaging.

RESULTS

Retrospective review of MR images revealed 21 Baker's cysts, one myxoid liposarcoma, one meniscal cyst, and 13 examinations with normal findings. The sonography reports revealed that the 21 Baker's cysts were correctly diagnosed, whereas the meniscal cyst and myxoid liposarcoma were misdiagnosed as Baker's cysts. Retrospective review of sonographic images showed a 100% sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in the diagnosis of Baker's cyst when hypoechoic or anechoic fluid was present between the semimembranosus and medial gastrocnemius tendons. No other sonographic characteristics were significant.

CONCLUSION

Identification of fluid between the semimembranosus and medial gastrocnemius tendons in communication with a posterior knee cyst indicates Baker's cyst with 100% accuracy.

Ultrasound in inflammatory disease

US may be used effectively to diagnose and treat a wide range of musculoskeletal inflammatory conditions. It is likely that its usage will increase with regards to such conditions especially in the management of rheumatology clinic patients.