Popliteal cysts in adults: a review

Atypical Calf Cyst Treated With Doxycycline Sclerotherapy: A Case Report

ABSTRACT

There are many types of cysts in the leg; the most common is a popliteal (Baker's) cyst. This occurs when synovial fluid fills the tissue plane between the medial head of the gastrocnemius and the semimembranosus muscle and is often associated with intraarticular knee pathology. Treatment for various types of cysts includes aspiration with or without fenestration, injections with corticosteroids, dextrose, or various sclerosing agents, and surgical excision. This case describes a 58-yr-old man with a large cyst measuring 14.7 × 2.7 × 3.1 cm in size in the lateral calf, within the lateral gastrocnemius, with atypical size and location for a calf cyst. Computed tomography arthrogram showed intraarticular communication with the knee. The cyst recurred after two aspirations and injections with 25% dextrose/lidocaine. Aspiration and injection with doxycycline resulted in temporary relief followed by recurrence. Complete cyst resolution occurred after final aspiration without injectate. The cyst was likely synovial based on location, intraarticular communication, and fluid analysis. We suspect that complete resolution may have been due to repeated aspiration and injection, essentially performing longitudinal cyst fenestration, with possible contribution from doxycycline injection. Further study of intracyst doxycycline injection with reaspiration after 10 mins for treatment of refractory cysts may be warranted.

Clinical Evidence Regarding the Dynamic of Baker Cyst Dimensions after Intermittent Vacuum Therapy as Rehabilitation Treatment in Patients with Knee Osteoarthritis

The Baker cyst (BC), also known as the popliteal cyst or parameniscal cyst, is a fluid-filled sac that normally develops in the back of the knee, between the semimembranosus and medial head of the gastrocnemius. We aimed to evaluate the effectiveness of physiotherapy (10 days of treatment) that associates intermittent vacuum therapy (IVT) on the lower limbs in the treatment of the BC, respectively, in its size reduction. Sixty-five patients with knee osteoarthritis using Kellgren-Lawrence criteria and the presence of BC (ultrasonography evaluation), were divided into the Control and Vacuum groups. We collected the following features: sex, age, level of education, occupation, environment, body mass index, Knee Injury and Osteoarthritis Outcome Score, Western Ontario, and McMaster Universities Osteoarthritis Index, the Functional Independence Measurement, the Fall Risk Score, and the Visual Analog Scale were recorded at baseline and after 10 days. Both groups are similar in terms of demographic features. Regarding the clinical functional parameters, the results elicit a statistically significant change in all parameters between admission and discharge, including the echo volume at BC. Physical medicine and rehabilitation increase the autonomy of patients with BC. Clinical-functional improvement begins in the first 10 days of complex rehabilitation treatment; it is statistically significant and is not different between the two groups, which brings an additional argument for the effectiveness of conservative therapy in the treatment of BC. Although IVT has not demonstrated its superiority over classical balneo-physical therapy, additional research, and long-term monitoring are needed to provide additional arguments regarding this aspect.

Diagnostic accuracy of ultrasound for the assessment of Baker's cysts: a meta-analysis

BACKGROUND

Baker's cyst is the most common cystic disease of the knee, and a fast and accurate diagnosis of Baker's cyst is essential for a better management. Ultrasound is a rapid, portable, widely available, inexpensive and noninvasive imaging modality. However, the diagnostic accuracy of ultrasound on Baker's cyst still remains undetermined. We conducted the first meta-analysis to comprehensively assess the accuracy of ultrasound for the detection of Baker's cyst.

METHODS

PubMed, Embase and Web of Science were searched from inception to July 14, 2022, without language restrictions. Studies providing cross-tabulations of ultrasound versus pathology (gold standard) or MRI (standard imaging technique) for diagnosis of Baker's cyst were included. Indicators for the diagnostic accuracy of ultrasound, including sensitivity, specificity and area under the curve, were calculated using a bivariate model. Sensitivity analysis was conducted to evaluate the heterogeneity and robustness of the results.

RESULTS

A total of 13 studies with 1,011 subjects (mean age 32.2 years; men 53.5%) met the inclusion criteria. The pooled sensitivity, specificity and area under the curve of ultrasound for diagnosis of Baker's cyst, compared with pathology, were 0.97 (95% confidence intervals: 0.73-1.00), 1.00 (0.98-1.00) and 1.00 (0.99-1.00), respectively. The pooled estimates of ultrasound versus MRI were 0.94 (0.87-0.98) for sensitivity, 1.00 (0.83-1.00) for specificity and 0.97 (0.95-0.98) for area under the curve. Sensitivity analysis did not change the results materially.

CONCLUSION

Ultrasound shows excellent diagnostic accuracy for the assessment of Baker's cyst and provides similar diagnostic information (absent or present) compared to MRI. Because of its advantages of low cost, portability and accessibility, ultrasound is likely to be a choice of imaging technique for screening Baker's cyst in clinical and population settings as well as in follow-ups.

Popliteal cysts are not a risk factor for lower extremity deep vein thrombosis

BACKGROUND

Popliteal cysts (PC) result from distension of the gastrocnemio-semimembranosous bursa. Published reports indicate coincident PC and deep vein thrombosis (DVT). Whether the presence of PC increase the risk of deep vein thrombosis (DVT) remains unclear.

METHODS

Lower extremity venous Duplex ultrasound (DUS) reports were evaluated across the Mayo Clinic Enterprise (Rochester, Minnesota, Jacksonville, Florida, Scottsdale, Arizona, and the Mayo Clinic Health System) in patients ≥ 18 years of age. Natural language processing (NLP) algorithms were created and validated to identify acute lower extremity DVT and PC from these reports. To determine whether there is a link between PC and lower extremity DVT, the frequency of PC among cases (ultrasounds with acute DVT) were compared to controls (ultrasounds without acute DVT).

RESULTS

A total of 357,703 lower extremities venous DUS were performed in 237,052 patients (mean age 63.3 ± 16.6, 54.4% were female) between 1992 and 2021. Acute DVT was identified in 32,572 (9.1%) DUS, and PC in 32,448 (9.1%). PC were seen in a lower frequency (8.0%) of ultrasounds with acute DVT than those without (9.2%) acute DVT (OR: 0.85, 95% CI: 0.82 to 0.89, p < 0.001). In a multivariate logistic regression model after adjusting for age, sex, and race, PCs were not positively associated with acute DVT (adjusted OR: 0.84, 95% CI: 0.81 to 0.88).

CONCLUSIONS

PC are an incidental finding or an alternative diagnosis on lower extremity venous DUS, a finding that increases significantly with age. PC were not a risk factor in the development of lower extremity DVT.

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound - Part I: Extraarticular Pathologies

The first part of the guidelines and recommendations for musculoskeletal ultrasound, produced under the auspices of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), provides information about the use of musculoskeletal ultrasound for assessing extraarticular structures (muscles, tendons, entheses, ligaments, bones, bursae, fasciae, nerves, skin, subcutaneous tissues, and nails) and their pathologies. Clinical applications, practical points, limitations, and artifacts are described and discussed for every structure. After an extensive literature review, the recommendations have been developed according to the Oxford Centre for Evidence-based Medicine and GRADE criteria and the consensus level was established through a Delphi process. The document is intended to guide clinical users in their daily practice.

Arthroscopic Internal Drainage with Cyst Wall Resection and Arthroscopic Internal Drainage with Cyst Wall Preservation to Treat Unicameral Popliteal Cysts: A Retrospective Case-Control Study

Objective

To compare the clinical efficacy and safety of arthroscopic internal drainage for the treatment of unicameral popliteal cysts with or without cyst wall resection.

Methods

This was a retrospective case–control study of 73 patients diagnosed with unicameral popliteal cysts from January 2012 to January 2019 who received arthroscopic treatment. The study included 38 cases with cyst wall resection (CWR group) and 35 cases with cyst wall preservation (CWP group). The CWR group consisted of 14 men and 24 women with an average age of 51.8 years, while the CWP group consisted of 13 men and 22 women with an average age of 52.0 years. All patients were examined for intra‐articular lesions and communicating ports by magnetic resonance imaging (MRI) prior to surgery, and recurrence of cysts was evaluated at the last follow‐up examination. Rauschning and Lindgren grade (R–L grade) and Lysholm score were used to evaluate clinical outcomes. In addition, operation time and complications were recorded.

Results

The average length of follow‐up was 24.2 months (range, 16 to 32 months). There were no considerable differences in age, gender, cyst size, Lysholm score, R–L grade and concomitant intra‐articular cases between the CWR group and CWP group prior to surgery (P > 0.05). The last follow‐up MRI scans showed that in the CWR group, the cyst disappeared in 25 cases and shrunk in 13 cases. In the CWP group, the cyst disappeared in 22 cases, shrunk in 12 cases and persisted in one case. There was no obvious difference in recurrence rate between the two groups (0% vs 2.9%, P = 0.899). At the last follow‐up, there were no differences in the R–L grade (P = 0.630) and Lysholm score (88.3 ± 5.6 points vs 90.1 ± 3.8 points, P = 0.071) between the two groups. Compared with the CWP group, operation time was significantly prolonged in the CWR group (38.3 ± 3.1 min vs 58.3 ± 4.4 min, P < 0.05). In the CWR group, three cases occurred fluid infiltration under the gastrocnemius muscle, which improved after pressure bandaging and cold compress. In another three cases, hematoma was found. The incidence of complications in the CWR group was markedly higher than that in the CWP group (15.8% vs 0%, P < 0.05). During the follow‐up period, none of the patients developed serious complications such as neurovascular injury, deep venous thrombosis, or infection.

Conclusion

For unicameral popliteal cysts, arthroscopic internal drainage combined with resection of the cyst wall did not further improve the clinical outcomes or reduce the recurrence rate, while prolonging the operation time and increasing the possibility of complications.

Bedside ultrasound-guided aspiration and corticosteroid injection of a baker's cyst in a patient with osteoarthritis and recurrent knee pain

Baker's cyst accompanying knee osteoarthritis represents a common cause of knee pain presenting to the emergency department. In this case report, a 56-year-old male presented with atraumatic left knee pain and swelling. Radiographically, he had tricompartmental osteoarthritis and was found to have a baker's cyst on duplex ultrasound. Using point-of-care ultrasound, the cyst was aspirated and corticosteroids were injected. The patient tolerated the procedure well and was discharged with a compression wrap and orthopedic follow-up. Baker's cyst aspiration with corticosteroid injection represents a safe alternative treatment option for patients. In some cases, this treatment may be definitive. Orthopedists currently use this procedure to reduce pain and improve function for patients with chronic knee ailments related to baker's cysts. As demonstrated in this case report, implementing this bedside procedure in the emergency department with orthopedic follow-up expands non-surgical, non-narcotic treatment options for patients with chronic knee pain secondary to Baker's cysts with osteoarthritis.

Ultrasound-guided arthroscopic communication enlargement surgery may be an ideal treatment option for popliteal cysts - indications and technique

PURPOSE

Several studies have shown an excellent success rate of communication enlargement surgery for popliteal cysts (Baker's cysts). Ultrasound-guided surgery can improve the accuracy of this procedure and may lead to better outcomes. This study describes a simple ultrasound-guided arthroscopic technique to manage popliteal cysts and reduce postoperative pain.

METHODS

After routine arthroscopic observation with a standard 2-portal approach, the arthroscope is redirected toward the posteromedial compartment from the anterolateral portal through the intercondylar notch. A posteromedial portal is then placed at this view. Subsequently, a contrast dye (indigo carmine) is injected into the popliteal cyst percutaneously using ultrasonography. This procedure makes it easier to find a capsular fold or valvular opening. The valvular opening between the semimembranosus and medial gastrocnemius is enlarged with a shaver and radiofrequency ablation. Cystectomy is not performed in any case. Finally, the irrigation fluid is suctioned, and the reduced cyst is visualized by ultrasound. Additionally, a periarticular multimodal drug injection is administered into the septum and inner wall of the cyst under ultrasound guidance.

CONCLUSIONS

Ultrasound-guided arthroscopic surgery for popliteal cysts can ensure reproducibility and be effective for postoperative pain relief. Thus, this combined procedure may be an optimal treatment option.

Isolation and Characterization of Human Synovial Fluid-Derived Mesenchymal Stromal Cells from Popliteal Cyst

Mesenchymal stem cells (MSCs) are multipotent progenitor cells in adult tissues. The aim of this study is to isolate and identify synovial fluid-derived mesenchymal stromal cells (SF-MSCs) from the popliteal cyst fluid of pediatric patients. SF-MSCs were collected from the popliteal cyst fluid of pediatric patients during cystectomy surgery. After cyst fluid extraction and adherent culturing, in vitro morphology, growth curve, and cell cycle were observed. The expression of stem cell surface markers was analyzed by flow cytometry, and expression of cell marker protein was detected by immunofluorescence. SF-MSCs were cultured in osteogenic, adipogenic, and chondrogenic differentiation medium. The differentiation potential of SF-MSCs was analyzed by alkaline phosphatase (Alizarin Red), Oil Red O, and Alcian blue. Antibody detection of human angiogenesis-related proteins was performed compared with bone marrow mesenchymal stem cells (BM-MSCs). The results show that SF-MSCs from the popliteal cyst fluid of pediatric patients showed a shuttle appearance and logarithmic growth. Flow cytometry analysis revealed that SF-MSCs were negative for hematopoietic lineage markers (CD34, CD45) and positive for MSC markers (CD44, CD73, CD90, and CD105). Interstitial cell marker (vimentin) and myofibroblast-like cell marker alpha-smooth muscle actin (α-SMA) were positive. These cells could differentiate into osteogenic, adipogenic, and chondrogenic lineages, respectively. Several types of human angiogenesis-related proteins were detected in the cell secretory fluid. These results show that we successfully obtained SF-MSCs from the popliteal cyst fluid of pediatric patients, which have the potential to be a valuable source of MSCs.

A Rare Case of Juvenile Idiopathic Arthritis following a Ruptured Baker’s Cyst in a Toddler

A Baker's cyst is usually an incidental finding in adults being investigated for a joint arthropathy, and its rupture preceding the diagnosis of juvenile idiopathic arthritis (JIA) is rare in children. Here, we describe a case of a 4-year-old girl who presented to the Emergency Department with right calf pain, swelling, and no preceding history of trauma. MRI confirmed a ruptured Baker's cyst with inflammatory arthropathy alongside an extensive synovial proliferation throughout the knee joint with large joint effusions and associated soft tissue oedema tracking superiorly and inferiorly along the medial head of gastrocnemius and anteriorly along the tibia. Further investigations revealed bilateral uveitis consistent with a diagnosis of juvenile idiopathic arthritis.

The fate of Baker's cysts at mid-term follow-up after total knee arthroplasty

AIMS

We report the natural course of Baker's cysts following total knee arthroplasty (TKA) at short- and mid-term follow-up.

METHODS

In this prospective case series, 105 TKA patients were included. All patients who received surgery had a diagnosis of primary osteoarthritis and had preoperatively presented with a Baker's cyst. Sonography and MRI were performed to evaluate the existence and the gross size of the cyst before TKA, and sonography was repeated at a mean follow-up time of 1.0 years (0.8 to 1.3; short-term) and 4.9 years (4.0 to 5.6; mid-term) after TKA. Symptoms potentially attributable to the Baker's cyst were recorded at each assessment.

RESULTS

At the one-year follow-up analysis, 102 patients were available. Of those, 91 patients were available for the 4.9-year assessment (with an 86.7% follow-up rate (91/105)). At the short- and mid-term follow-up, a Baker's cyst was still present in 87 (85.3%) and 30 (33.0%) patients, respectively. Of those patients who retained a Baker's cyst at the short-term follow-up, 31 patients (35.6%) had popliteal symptoms. Of those patients who continued to have a Baker's cyst at the mid-term follow-up, 17 patients (56.7%) were still symptomatic. The mean preoperative cyst size was 14.5 cm² (13.1 to 15.8). At the short- and mid-term follow-up, the mean cyst size was 9.7 cm² (8.3 to 11.0) and 10.4 cm² (9.8 to 11.4), respectively. A significant association was found between the size of the cyst at peroperatively and the probability of resolution, with lesions smaller than the median having an 83.7% (36/43) probability of resolution, and larger lesions having a 52.1% (25/48) probability of resolution (p < 0.001). At the mid-term follow-up, no association between cyst size and popliteal symptoms was found.

CONCLUSION

At a mean follow-up of 4.9 years (4.0 to 5.6) after TKA, the majority (67.0%, 61/91) of the Baker's cysts that were present preoperatively had disappeared. The probability of cyst resolution was dependent on the size of the Baker's cyst at baseline, with an 83.7% (36/43) probability of resolution for smaller cysts and 52.1% (25/48) probability for larger cysts. Cite this article: Bone Joint J. 2020;102-B(1):132-136.

The prevalence of Baker cyst in relation to the arrangement pattern between the medial head of gastrocnemius tendon and the semimembranosus tendon

PURPOSE

The purpose of this study was to investigate whether Baker cyst (BC) was related to the specific arrangement of the medial head of gastrocnemius tendon (MHGT) and the semimembranosus tendon (SMT).

MATERIALS AND METHODS

Patients who underwent knee MRI with "Baker cyst" in PACS from August 2017 to February 2018 were included in this study. Patients who did not have BC in a knee MRI performed during the same period were included in the control group. A total 210 patients were selected for inclusion in this study. For the imaging analysis, the arrangement pattern between MHGT and SMT was classified into three types: type 1, concave; type 2, flat; and type 3, convex. When imaging analysis was performed, the amount of effusion, the presence of osteoarthritis, and major ligament and meniscal tears were also described. Univariate and multivariate logistic regression analyses were performed. Statistical significance was considered at p < 0.05.

RESULTS

The frequency of types 1, 2, and 3 was statistically significant depending on the presence or absence of BC (p < 0.001). The frequency of type 3 was the highest in the presence of BC, while that of type 1 was the highest in the absence of BC. BC was more common in type 2 (OR = 2.54; 95% CI = 1.27-5.07) and type 3 (OR = 4.09; 95% CI = 1.88-8.89).

CONCLUSION

BC is more likely to occur in patients with SMT having a convex shape for MHGT.

KEY POINTS

• Based on axial image of MRI only, one can predict which patients are morphologically more prone to develop a Baker cyst. • On axial images of MRI, Baker cyst is more likely to occur in patients with semimembranosus tendon having a convex shape for medial head of gastrocnemius tendon. • Baker cyst is not associated with the amount of effusion, OA, or internal derangement.

Hip and Knee Injuries

Hip and knee injuries are a common presenting concern for patients to a primary care office. This pathology represents a large differential and it can often be a diagnostic challenge for providers to determine the etiology of a patient's symptoms. This article discusses several of the most common causes for hip and knee pain while providing an evidence based review of physical examination maneuvers, imaging studies and treatment modalities to assist a primary care provider when encountering active patients with underlying hip or knee pain.

Compartment syndrome secondary to Baker's cyst rupture: A case report and up-to-date review

Baker's cyst is a distention or enlargement of the gastrocnemius-semimembranosus bursa toward the popliteal fossa which is usually associated with intra-articular pathologies. Rupture or dissection of the Baker's cyst results in extravasation of the cyst content into the calf within intermuscular space under the fascia. This clinical entity, also called pseudothrombophlebitis, is a self-limited condition that usually resolves with supportive treatment. However, in patients using anticoagulants, excessive hemorrhage may cause compartment syndrome in case of cyst rupture. Early diagnosis of compartment syndrome is the most important step in preventing permanent disability. Therefore, compartment syndrome should be kept in mind and ruled out in a patient with pseudothrombophlebitis syndrome under anticoagulation therapy.

Epidermal inclusion cyst of the knee

Epidermoid cysts are asymptomatic, slowly enlarging, firm to fluctuant, dome-shaped lesions. Epidermoid cysts frequently appear on the trunk, neck, face, and scrotum, behind the ears and in the palmoplantar region. We review all the cases of epidermoid cyst of the knee and present a case of non-traumatic-induced epidermal cyst in the popliteal fossa of a 66-year-old male with 10-year history of right knee swelling, which appeared firstly as a small mass 2 × 2 cm in the popliteal aspect of the knee. The mass was increasing gradually in size until 2 years ago when it increased suddenly to gain the dimensions of 4 × 6 cm. MRI of the right knee revealed a well-defined cystic lesion in the subcutaneous tissue measuring about 7 × 5 × 5 cm containing internal debris and septations. He underwent complete surgical excision of the mass. The pathological results revealed an epidermal inclusion cyst. To the best of our knowledge, this is the second description for epidermal inclusion cyst involving the popliteal fossa. We were able to retrieve three cases of epidermal cyst of the knee from the literature since its first description in 2004. Including our case, we had a total of four cases of epidermal cyst of the knee. Three males and one female constituted the patients' sample. The mean age for the patients is 55. The epidermal cyst occurred equally in both knees. The popliteal fossa was the location for two epidermal cysts. Similarly, the prepatellar region was the location for another two cysts.

Infected Baker's Cyst: A New Classification, Diagnosis and Treatment Recommendations

Introduction:

Baker’s cyst has a high prevalence in adult population. Despite being usually asymptomatic, cyst complications may develop, such as an infection, rupture and content dissemination into the calf. This clinical presentation has a low incidence with few reports in the literature. We have not found any publication describing a systematic approach for its treatment. The purpose of this study is to propose a new classification, diagnosis, and treatment recommendations based on a case report and a literature review to guide physicians on the best course of treatment.

Case Report:

A 53-year-old man presented with sudden left popliteal pain associated with progressive knee and calf swelling and limited knee flexion. After the initial evaluation, a Baker’s cyst rupture and dissemination into the calf, associated with a septic arthritis, were diagnosed. An arthroscopic surgical irrigation of the knee and open debridement of the calf collection were performed.

Conclusion:

Our classification may allow an accurate and structured description of the different stages of Baker’s cyst presentations, with simplification of the clinical description, diagnosis, and treatment approaches.

Is There A Relationship Between Three-Dimensionally Measured Baker's Cyst Volume and Knee Pathologies?

Objective

Baker's cyst (BC) is also known as popliteal cyst. To evaluate its effect on intra-articular pathology, it is important to have the exact volume of the cyst. As BC may change its shape due to mass effect of the surrounding anatomic structures, it is difficult to measure the exact volume of BC. This study examined the relationship between three-dimensionally measured BC volume and symptomatic intra-articular knee pathologies.

Materials and Methods

The magnetic resonance (MR) images of 45 patients with symptomatic knees were retrospectively examined.The BC volumes were measured via volumetric analysis. The joint effusion was examined in the sagittal plane in T2-proton density-weighted images. The medial plicae were assessed in accordance with the modified Sakakibara classification. Using the MR images, the meniscuses were classified in accordance with the meniscus rupture classification of Stoller et al. The cartilaginous lesions were analyzed using an MR grading system.In this study, correlations between the following measures were analyzed: BC volume and effusion level, medial plica presence, medial femoral condyle, medial tibial condyle, lateral femoral condyle and lateral tibial condyle cartilage degeneration, and medial meniscus anterior horn, medial meniscus posterior horn, lateral meniscus anterior and posterior horn ruptures.

Results

Cartilage degeneration, medial plicae, increase in intra-articular effusion, and increase in the BC volume were found to be statistically significant (p<0.01).

Conclusion

Cartilage degeneration, medial plicae, and increase in intra-articular effusion may increase the BC volume. We believe that this study may contribute to clinicians in understanding the relationship between BC volume changes and pathologies causing intra-articular knee symptoms.

Extra-articular endoscopic excision of symptomatic popliteal cyst with failed initial conservative treatment: A novel technique

To reduce the damage to posteromedial knee capsule, we developed a direct extra-articular arthroscopic approach for excision of symptomatic popliteal cysts. This study aimed to demonstrate the surgical technique and present the 2-year follow-up results. Cystectomy is performed by extra-articular surgical approach through a high posteromedial portal. Twenty-one consecutive patients diagnosed of symptomatic popliteal cysts with failed initial conservative treatments were included. At a median follow-up of 29.4 months, all knees had improved clinical function assessed by Rauschning and Lindgren knee classification (p<0.001). The cysts were either disappeared (95.2%) or reduced in size (4.8%). Only one (4.8%) patient had recurrent cyst, which was solved after ultrasound-guided aspiration. This direct extra-articular arthroscopic technique could be a feasible alternative for treatment of symptomatic popliteal cysts.

Pediatric musculoskeletal ultrasound

The expanding applications of musculoskeletal ultrasound include many examinations that are new to pediatric radiologists but are well known to our adult colleagues. In this review we present an introduction and guide to some of these entities for pediatric radiologists making inroads into the world of musculoskeletal ultrasound.

The Unilateral Swollen Lower Limb: Etiology, Investigation, and Management

The swollen lower limb, a common finding in routine clinical practice, is clinically challenging. The cause underlying this problem is often multifactorial, and its management may involve different specialties. It is important, though difficult, to avoid unnecessary and expensive investigations. The aim of this article is to provide an overview of the management of this problem by addressing the common causes, methods of assessment, diagnosis, and therapeutic options.

Bakers' cyst and tibiofemoral abnormalities are more distinctive MRI features of symptomatic osteoarthritis than patellofemoral abnormalities

OBJECTIVE

To investigate which structural MR abnormalities discriminate symptomatic knee osteoarthritis (OA), taking co-occurrence of abnormalities in all compartments into account.

METHODS

The Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort aged 45-65 years. In 1285 participants (median age 56 years, 55% women, median body mass index (BMI) 30 kg/m(2)), MRI of the right knee were obtained. Structural abnormalities (osteophytes, cartilage loss, bone marrow lesions (BMLs), subchondral cysts, meniscal abnormalities, effusion, Baker's cyst) at 9 patellofemoral and tibiofemoral locations were scored following the knee OA scoring system. Symptomatic OA in the imaged knee was defined following the American College of Rheumatology criteria. Logistic ridge regression analyses were used to investigate which structural abnormalities discriminate best between individuals with and without symptomatic OA, crude and adjusted for age, sex and BMI.

RESULTS

Symptomatic knee OA was present in 177 individuals. Structural MR abnormalities were highly frequent both in individuals with OA and in those without. Baker's cysts showed the highest adjusted regression coefficient (0.293) for presence of symptomatic OA, followed by osteophytes and BMLs in the medial tibiofemoral compartment (0.185-0.279), osteophytes in the medial trochlear facet (0.262) and effusion (0.197).

CONCLUSIONS

Baker's cysts discriminate best between individuals with and without symptomatic knee OA. Structural MR abnormalities, especially in the medial side of the tibiofemoral joint and effusion, add further in discriminating symptomatic OA. Baker's cysts may present as a target for treatment.

Arthroscopic patterns of the poster-medial aspect of the knee joint: classification of the gastrocnemius-semimembranosus gateway and its relationship with Baker's cyst

BACKGROUND

The gastrocnemius-semimembranosus bursa may communicate with the knee joint. The arthroscopic anatomy of the posteromedial aspect varies depending on the angle of the oblique popliteal ligament, the level at which it crosses the medial gastrocnemius tendon, and its relationship with the capsular joint and synovia. The aim of this paper is to identify possible patterns, and to evaluate their characteristics and their relationship with Baker's cyst.

METHODS

data archived from 185 consecutive arthroscopies were evaluated; an anatomic description and classification was carried out; the percentages of association with BC and the associated pathologies were reported.

RESULTS

The different anatomies were classified into six groups based on the relationship above the medial gastrocnemius tendon, the capsular joint and synovia. The prevalence of Baker's cyst was 28.3%. The main associated intra-articular pathological condition was the contemporary presence of a meniscal tear and chondropathy.

CONCLUSION

Exploration of the posterior aspect of the knee must be performed routinely. Knowing the possible anatomy patterns of the posteromedial arthroscopic aspect of the knee joint could help to identify the cyst and its gateway, thus facilitating its treatment.

LEVEL OF THE EVIDENCE

III.

A Huge Infected Popliteal Cyst Dissecting into Gastrocnemius Mimicking Calf Abscess

We report a case of a chronic huge popliteal cyst, which dissected into the gastrocnemius without rupture and was complicated with acute primary infection mimicking calf abscess upon presentation. To the best of our knowledge, it is the largest popliteal cyst with intramuscular dissection reported in the literature. It is noteworthy that infected popliteal cyst is a rare differential diagnosis of calf abscess.

BAKER'S CYST

Baker's cysts are located in the posteromedial region of the knee between the medial belly of the gastrocnemius muscle and semimembranosus tendon. In adults, these cysts are related to intra-articular lesions, which may consist of meniscal lesions or arthrosis. In children, these cysts are usually found on physical examination or imaging studies, and they generally do not have any clinical relevance. Ultrasound examination is appropriate for identifying and measuring the popliteal cyst. The main treatment approach should focus on the joint lesions, and in most cases there is no need to address the cyst directly. Although almost all knee cysts are benign (Baker's cysts and parameniscal cysts), presence of some signs makes it necessary to suspect malignancy: symptoms disproportionate to the size of the cyst, absence of joint damage (e.g. meniscal tears) that might explain the existence of the cyst, unusual cyst topography, bone erosion, cyst size greater than 5 cm and tissue invasion (joint capsule).

Baker's Cyst: Diagnostic and Surgical Considerations

Context:

Popliteal synovial cysts, also known as Baker’s cysts, are commonly found in association with intra-articular knee disorders, such as osteoarthritis and meniscus tears. Histologically, the cyst walls resemble synovial tissue with fibrosis evident, and there may be chronic nonspecific inflammation present. Osteocartilaginous loose bodies may also be found within the cyst, even if they are not seen in the knee joint. Baker’s cysts can be a source of posterior knee pain that persists despite surgical treatment of the intra-articular lesion, and they are routinely discovered on magnetic resonance imaging scans of the symptomatic knee. Symptoms related to a popliteal cyst origin are infrequent and may be related to size.

Evidence Acquisition:

A PubMed search was conducted with keywords related to the history, diagnosis, and treatment of Baker’s cysts—namely, Baker’s cyst, popliteal cyst, diagnosis, treatment, formation of popliteal cyst, surgical indications, and complications. Bibliographies from these references were also reviewed to identify related and pertinent literature.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

Baker’s cysts are commonly found associated with intra-articular knee disorders. Proper diagnosis, examination, and treatment are paramount in alleviating the pain and discomfort associated with Baker’s cysts.

Conclusion:

A capsular opening to the semimembranosus–medial head gastrocnemius bursa is a commonly found normal anatomic variant. It is thought that this can lead to the formation of a popliteal cyst in the presence of chronic knee effusions as a result of intra-articular pathology. Management of symptomatic popliteal cysts is conservative. The intra-articular pathology should be first addressed by arthroscopy. If surgical excision later becomes necessary, a limited posteromedial approach is often employed. Other treatments, such as arthroscopic debridement and closure of the valvular mechanism, are not well studied and cannot yet be recommended.

Treatment of popliteal cysts via arthroscopic enlargement of unidirectional valvular slits

OBJECTIVE

The aim of the present study was to investigate the efficacy of arthroscopic enlargement of unidirectional valvular slits for the treatment of popliteal cysts and to evaluate potential factors affecting the outcomes of our arthroscopic procedure.

METHODS

Twenty-nine patients aged 43-77 years with popliteal cysts were treated with arthroscopic cyst decompression. Surgery was performed via two posterior portals after creating a transseptal portal. Rauschning and Lindgren clinical score, magnetic resonance images, and osteoarthritic grade were evaluated pre- and postoperatively, and cartilage degeneration class was confirmed via arthroscopy. The mean follow-up period was 22.9 ± 14.6 months (range, 9-60 months).

RESULTS

Twelve cysts disappeared completely (group D), while 16 reduced and one enlarged (group R) in size by the final follow-up. Twenty-two (75.9%) of 29 popliteal cysts diminished to a volume that was less than 10% of the preoperative volume. Clinical scores improved in 93.1% of the patients, and more patients (68.8%) in group R had positive joint effusion at the final follow-up compared with group D (17.7%; p < 0.01).

CONCLUSIONS

Arthroscopic cyst decompression was effective in the treatment of symptomatic popliteal cysts. Intra-articular pathologies associated with joint effusion should be corrected simultaneously.

Pyogenic Baker cyst in a patient with psoriatic arthritis during etanercept therapy

Patients with psoriatic arthritis (PsA) are at increased risk of infection due to disease course or treatment-related immunodeficiency. We describe a patient with a 10-year history of PsA, with arthritis of the right knee and pain and edema in the right calf, treated with the TNFa inhibitor etanercept for 6 months. Ultrasound showed accumulation of hypoechoic fluid, which was aspirated and was positive for staphylococcus and aspergillus. The patient recovered after surgical drainage and four weeks of antibiotic and antifungal therapy.

Baker's Cyst Filled with Hematoma at the Lower Calf

Baker's cyst is a distension of the gastrocnemius-semimembranosus bursa of the knee, which communicates with the posterior portion of the joint capsule. Baker's cyst is commonly located in the inferomedial or superficial layers of the knee joint and rarely extends laterally or proximally. Complications of Baker's cysts are dissection, rupture, pseudothrombophlebitis, leg ischemia, nerve entrapment, and compartment syndrome. However, hematomas in the Baker's cyst have not been reported in Korea. We report a rare case of hematoma in the Baker's cyst with subfascial extension into the calf. The hematoma was demonstrated by magnetic resonance imaging and removed by mass excision.

Cysts and cystic-appearing lesions of the knee: A pictorial essay

Cysts and cystic-appearing lesions around the knee are common and can be divided into true cysts (synovial cysts, bursae, ganglia, and meniscal cysts) and lesions that mimic cysts (hematomas, seromas, abscesses, vascular lesions, and neoplasms). The specific anatomic location of the cystic lesion often permits the correct diagnosis. In difficult cases, identifying a cystic mass in an atypical location and/or visualizing internal solid contrast enhancement on magnetic resonance imaging (MRI) should raise concern for a neoplasm and the need for further evaluation and intervention.

Arthroscopic anatomic study of posteromedial joint capsule in knee joint associated with popliteal cyst

PURPOSE

The purpose of this study was to examine the arthroscopic anatomy of posteromedial capsule and magnetic resonance imaging (MRI) findings in internal derangement of the knee joint and to analyze the relationship between popliteal cysts and the posteromedial capsule.

METHODS

From 2011 to 2012, a prospective study included 194 knees of consecutive arthroscopic surgeries for assorted knee problems. The anatomy of the posteromedial joint capsule was evaluated arthroscopically and divided into three types by the presence of capsular fold and opening: no capsular fold and no opening (type I), capsular fold without opening (type II), capsular fold with opening (type III). The presence and size of popliteal cyst were documented by MRI.

RESULTS

Type I was observed in 160 knees (82.5 %), type II in 10 (5.1 %) and type III in 24 (12.4 %). Popliteal cysts were found in 25 knees (12.9 %) by MRI. Of these cases, symptomatic popliteal cysts were identified in 12 knees (6.9 %). On 160 knees demonstrated to be type I, only 3 knees (1.9 %) had popliteal cysts in MRI, 6 knees (60 %) in 10 knees of type II and 16 knees (66.7 %) in 24 knees of type III. Therefore, there was a statistically significant relationship between the type of anatomy in the posteromedial capsule and the popliteal cyst (p < 0.001).

CONCLUSION

An association between popliteal cyst and arthroscopic anatomy of posteromedial capsule was demonstrated. Comprehensive understanding and knowledge of the arthroscopic anatomy of posteromedial capsule would contribute to the arthroscopic approach in understanding the pathogenesis of popliteal cyst.

STUDY DESIGN

Development of diagnostic criteria on basis of consecutive patients.

LEVEL OF EVIDENCE

2.

Popliteal cysts and subgastrocnemius bursitis are associated with knee symptoms and structural abnormalities in older adults: a cross-sectional study

Introduction

The role of popliteal cysts and subgastrocnemius bursitis in knee joint homeostasis is uncertain. The aim of this study is to describe cross-sectional associations between popliteal cysts, subgastrocnemius bursitis, knee symptoms and structural abnormalities in older adults.

Methods

A cross-sectional sample of 900 randomly-selected subjects (mean age 63 years, 48% female) were studied. Knee pain, stiffness and dysfunction were assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire. Radiographic knee osteophyte and joint space narrowing (JSN) were recorded. Magnetic resonance imaging (MRI) was utilized to assess popliteal cysts, subgastrocnemius bursitis, cartilage defects and bone marrow lesions (BMLs).

Results

Popliteal cysts were present in 11.7% and subgastrocnemius bursitis in 12.7% of subjects. Subgastrocnemius bursitis was more common in those with popliteal cyst (36.2% versus 9.7%, P <0.01). In multivariable analyses, popliteal cysts were significantly associated with increased osteophytes in both medial and lateral tibiofemoral compartments while subgastrocnemius bursitis was associated with increased osteophytes and JSN in the medial tibiofemoral compartment. Both were significantly associated with cartilage defects in all compartments, and with BMLs in the medial tibiofemoral compartment. Furthermore, both popliteal cysts and subgastrocnemius bursitis were significantly associated with increased weight-bearing knee pain but these associations became non-significant after adjustment for cartilage defects and BMLs.

Conclusions

Popliteal cysts and subgastrocnemius bursitis are associated with increased symptoms as well as radiographic and MRI-detected joint structural abnormalities. Longitudinal data will help resolve if they are a consequence or a cause of knee joint abnormalities.

Compressive neuropathy of the posterior tibial nerve at the lower calf caused by a ruptured intramuscular baker cyst

Baker cyst is an enlargement of the gastrocnemius-semimembranosus bursa. Neuropathy can occur due to either direct compression from the cyst itself or indirectly after cyst rupture. We report a unique case of a 49-year-old man with left sole pain and paresthesia who was diagnosed with posterior tibial neuropathy at the lower calf area, which was found to be caused by a ruptured Baker cyst. The patient's symptoms resembled those of lumbosacral radiculopathy and tarsal tunnel syndrome. Posterior tibial neuropathy from direct pressure of ruptured Baker cyst at the calf level has not been previously reported. Ruptured Baker cyst with resultant compression of the posterior tibial nerve at the lower leg should be included in the differential diagnosis of patients who complain of calf and sole pain. Electrodiagnostic examination and imaging studies such as ultrasonography or magnetic resonance imaging should be considered in the differential diagnosis of isolated paresthesia of the lower leg.