MR Imaging of Cysts, Ganglia, and Bursae About the Knee

Neoplastic and Non-neoplastic Soft Tissue Lesions Around the Knee

Neoplastic and non-neoplastic soft tissue masses around the knee are often incidental findings. Most of these lesions are benign with typical imaging characteristics that allow a confident diagnosis. However, some of these incidental neoplastic masses are characterized by morbidity and potential mortality. This review highlights the typical aspects of these lesions, facilitating a correct diagnosis.

MRI-based synthetic CT in the detection of knee osteoarthritis: Comparison with CT

Magnetic resonance Imaging is the gold standard for assessment of soft tissues; however, X-ray-based techniques are required for evaluating bone-related pathologies. This study evaluated the performance of synthetic computed tomography (sCT), a novel MRI-based bone visualization technique, compared with CT, for the scoring of knee osteoarthritis. sCT images were generated from the 3T T1-weighted gradient-echo MR images using a trained machine learning algorithm. Two readers scored the severity of osteoarthritis in tibiofemoral and patellofemoral joints according to OACT, which enables the evaluation of osteoarthritis, from its characteristics of joint space narrowing, osteophytes, cysts and sclerosis in CT (and sCT) images. Cohen's κ was used to assess the interreader agreement for each modality, and intermodality agreement of CT- and sCT-based scores for each reader. We also compared the confidence level of readers for grading CT and sCT images using confidence scores collected during grading. Inter-reader agreement for tibiofemoral and patellofemoral joints were almost-perfect for both modalities (κ = 0.83-0.88). The intermodality agreement of osteoarthritis scores between CT and sCT was substantial to almost-perfect for tibiofemoral (κ = 0.63 and 0.84 for the two readers) and patellofemoral joints (κ = 0.78 and 0.81 for the two readers). The analysis of diagnosis confidence scores showed comparable visual quality of the two modalities, where both are showing acceptable confidence levels for scoring OA. In conclusion, in this single-center study, sCT and CT were comparable for the scoring of knee OA.

Baker's Cyst

The authors present a case of a Baker's cyst in the right leg of an 86-year-old woman, whose presentation was more typical for a deep venous thrombosis. Both conditions have inflammation and acute calf pain. The clinical manifestations, imaging findings, and treatment of this common emergency department presentation are discussed.

Ganglion cyst at the proximal tibiofibular joint - A rare cause of compression neuropathy of the peroneal nerve

Ganglion cysts are fluid filled sacs which develop near joints and tendons and are usually asymptomatic. Lower limb ganglion cysts are rare occurrences especially those situated around joint spaces causing nerve compression. We present the case of a 68 year-old female with history of progressive swelling in the left antero-lateral leg, associated with pain, and neurological symptoms of peroneal nerve compression. Magnetic resonance imaging (MRI) revealed a large proximal tibiofibular joint ganglion cyst causing peroneal nerve compression. One year following the left sided presentation, the patient presented with similar but less severe symptoms in her right antero-lateral leg. MRI revealed a small juxta-articular ganglion cyst in the right proximal tibiofibular joint space. We discuss etiology, symptoms, and management of lower limb ganglion cysts.

Unusual Presentation of Extensor Tendon Rupture Caused by a Dorsal Wrist Synovial Cyst

Synovial cysts are juxta-articular-fluid–filled collections that are lined by synovial cells, distinguishing them from a very close cystic lesion, which is the ganglion cyst. They usually present with pain and unpleasant appearance; here we present a case of wrist synovial cyst that caused extensor tendon rupture. A 50-year-old woman presented to our clinic with a cystic lesion on the dorsum of her wrist, with an inability to extend her index finger. The lesion was found intraoperatively engulfing the extensors of the index and causing a rupture. The cyst was excised and the tendon was reconstructed; pathology report confirmed the lesion as synovial cyst. Synovial cysts and ganglion cysts are two different entities but they have been used interchangeably in the literature; pathology is the only way to differentiate between them because they usually present with identical scenarios. None of them were reported to cause extensor tendon rupture, as presented in our article. Synovial cysts can cause rupture to extensor tendons if they arise from the sheath, and it is better to anticipate synovial cyst and remove it surgically before causing any further damage, if the lesion appeared to rise from the tendon sheath on further imaging.

Ultra-high-frequency ultrasound of superficial and musculoskeletal structures in the pediatric population

Because of its relatively low cost, lack of ionizing radiation and great versatility, US is considered the imaging modality of choice to evaluate a large variety of pediatric conditions. Imaging of superficial structures and small anatomical parts can be at times limited with standard US. Recent advances in technology yielded ultra-high-frequency US systems that are capable of scanning with frequencies as high as 70 MHz and resolutions of 30 μm. This technology, approved by the United States Food and Drug Administration, has not been widely used in the clinical setting. It has the potential to become a powerful diagnostic tool in clinical practice, especially in the evaluation of infants, given their inherent body habitus. Our main objective is to discuss the use of ultra-high-frequency US at a tertiary care center. This pictorial essay presents a gamut of pediatric pathologies pertaining to imaging of the soft tissues and the superficial and musculoskeletal structures. Our aim in this pictorial essay is to highlight and illustrate the role of ultra-high-frequency US in improving the depiction of common and less common pathologies. We think it also helps to gain a new understanding of the normal anatomy in the pediatric population and to display specific features not shown by standard US and, in certain cases, ones that lead to a change in diagnosis.

Clinical Relevance and Immunohistochemical Patterns of Silent Pituitary Adenomas: 10 Years of Single-centre Experience

BACKGROUND

Silent pituitary adenomas are clinically non-functional (i.e., without clinically evident pituitary hormone production).

INTRODUCTION

The aim of this study was to investigate subjects with silent pituitary adenomas for possible variations in their clinical status.

METHODS

A total of 102 patients who had undergone surgery for pituitary adenoma and had been diagnosed with silent pituitary adenoma was included in the study. The patients' preoperative and postoperative hormonal parameters and magnetic resonance imaging (MRI) features were collected, and pathological specimens were re-evaluated.

RESULTS

Immunohistochemistry results of the 102 patients were as follows: hormone-negative adenomas (n=35) 35.5%; FSH+LH-positivity (n=32) 31.3%; ACTH-positivity (n=11) 10.7%; α-subunit- positivity (n= 9) 8.8%; prolactin-positivity (n=8) 7.8%; GH-positivity (n=6) 5.4%; and plurihormonal adenoma (n=1). The mean sizes of SGA, SGHA, and SCA were 28.0±12.7, 30.0±16.0, and 27.7±8.9mm (p>0.05), respectively. With the exception of silent gonadotroph adenomas (SGAs), female gender dominance was shown in patients with silent growth hormone adenoma (SGHA) and silent corticotroph adenoma (SCA). Although no clinical relevance was observed in relation to hormonal excess, preoperative GH (4.21±4.6, vs. 0.27±0.36 p=0.00) was slightly more elevated in SGHA than in GH-negative adenomas. Additionally, preoperative basal ACTH values (47.3±28.7 vs. 23.9±14.4, p=0.003) were also higher in SCA compared to the other types. Our findings revealed SCAs to be of more aggressive behaviour than SGHAs and SGAs due to invasiveness in radiological imaging, their elevated re-operation, and postoperative ACTH values.

CONCLUSION

Silent pituitary adenomas represent a challenging diagnostic tumour group. Careful initial evaluation of patients with pituitary adenomas should consider any mild signs and symptoms of functionality, particularly in cases of GH- and ACTH-secreting adenomas.

Bone Tumors Occurring in the Soft Tissues: A Review of the Clinical, Imaging, and Histopathologic Findings

Although rare in everyday practice, malignancies that classically arise from bone or cartilage have been reported to arise de novo in various soft tissues in the body, resulting in a diagnostic challenge for the clinician, radiologist, and pathologist. Differential diagnoses of bone tumors often depend on anatomic location of the lesion. For example, the classic location of osteosarcoma is in the metaphysis of long bones about the knee. Histologically osteosarcoma is characterized by tumor cells that directly produce osteoid, bone, or cartilaginous matrix. In extraskeletal osteosarcoma, the clinical and radiologic picture is very different from a conventional osteosarcoma. They occur in older patients, present as a soft tissue mass often coincidentally following trauma and have a worse prognosis. The imaging characteristics are often nonspecific with mineralized elements in a well-defined soft tissue mass. The mineralized elements may or may not be visible. Magnetic Resonance sequences demonstrate a well circumscribed soft tissue mass with hemorrhagic and enhancing solid components. The pathologic features of extraskeletal osteosarcoma on a microscopic scale are identical to that of skeletal lesions. Likewise, conventional chondrosarcomas present in older patients with a growing, painful soft tissue prominence most commonly involving the long tubular bones. In extraskeletal chondrosarcoma however, the presentation is in somewhat younger patients with a painful soft tissue prominence typically in the head (meninges), neck, or upper leg. The pathologic features are most often that of a myxoid chondrosarcoma which is characterized by strands of small cells over a myxoid matrix. Imaging features include chondroid matrix, heterogenous contrast enhancement, and amorphous internal calcification on Computed Tomography. On Magnetic Resonance sequences the matrix has a low signal on all sequences, and variable inhomogeneity depending on grade of the lesion. Other extraskeletal bone tumors include Ewing's sarcoma and osteoid osteoma amongst other lesions. Although these malignancies may be rare clinical entities, they often exhibit characteristic clinical, imaging, and histopathological findings although differing in treatment and prognosis. Knowledge of these and other common mimicking lesions will help guide the clinician and radiologist to make an accurate diagnosis.

Inconsistent Use of Terminology and Different Treatment Outcomes of Venous Adventitial Cystic Disease: A Proposal for Reporting Standards

Adventitial cystic disease (ACD) is a very rare condition characterized by the accumulation of a cyst filled with gelatinous substance in the adventitia of a vessel adjacent to the joint area. The cyst usually compresses the vessel lumen, causing claudication or leg swelling. The disease usually affects the popliteal artery. However, several cases of venous ACDs particularly in the common femoral or external iliac vein have been reported. The definition, diagnosis, and optimal treatment of ACD remain controversial because of its rarity and the inconsistent use of terminology. The heterogeneity of the reported cases is more prominent in venous ACD. Herein, the accurate terminology of cysts correlated to the joint (synovial cyst, ganglion cyst, and adventitial cyst) and the pathogenesis, anatomy, and optimal therapy of venous ACD are discussed in detail to establish reporting standards for future studies.

Radiographic/MR Imaging Correlation of Soft Tissues

MR imaging is nowadays regarded as the preferred imaging modality for evaluation of soft tissue lesions. As plain radiographs are often the first step in evaluation of musculoskeletal disorders, identification of subtle soft tissue signs may be helpful to select patients who need to be referred for subsequent MR imaging. Although not very sensitive, certain plain film findings, such as intralesional calcification or gas, may allow one to make to a more specific tissue diagnosis and may obviate the need for invasive diagnostic procedures and potential harmful treatment.

Giant infrapatellar ganglion cyst of Hoffa's fat pad

We present the case of a 36-year-old woman who works as a kindergarten teacher, often she is kneeling on her knees due to the nature of the job. Since a year ago, she noticed that her right knee was swelling. She had an orthopaedic examination when she could no longer bend her knee. Inspection and palpation revealed the swelling of the anterior and anterior-lateral aspect of the knee. MRI imaging revealed a large, sharply defined, lobulated lesion of the infrapatellar fat pad. After the surgical incision, a lobular lesion was found and surgically removed. Histological analysis confirmed a ganglion cyst.

Magnetic Resonance Imaging of Cysts, Cystlike Lesions, and Their Mimickers Around the Knee Joint

While interpreting routine magnetic resonance imaging (MRI) of the knee joint, a radiologist may encounter various cystic lesions such as ganglion, synovial, and meniscal cysts, among others. In some cases, MRI may demonstrate cystlike lesions around the knee due to fluid distention of normal bursa and recesses, the diagnosis of which should not be difficult if a radiologist is familiar with their characteristic location and MRI appearance. In addition, there are cyst mimickers such as hematomas, abscesses, vascular lesions, and neoplasms around knee joint that may pose a diagnostic challenge on routine MRI. Due to their atypical location and variable morphology, contrast administration is helpful as the enhancement pattern aids to differentiate them from cysts and cystlike lesions. This pictorial essay aims to classify cysts, cystlike lesions, and cyst mimickers in and around the knee joint based on their anatomic location and highlight their characteristic MRI features.

The iliotibial tract: imaging, anatomy, injuries, and other pathology

The iliotibial tract, also known as Maissiat's band or the iliotibial band, and its associated muscles function to extend, abduct, and laterally rotate the hip, as well as aid in the stabilization of the knee. A select group of associated injuries and pathologies of the iliotibial tract are seen as sequela of repetitive stress and direct trauma. This article intends to educate the radiologist, orthopedist, and other clinicians about iliotibial tract anatomy and function and the clinical presentation, pathophysiology, and imaging findings of associated pathologies. Specifically, this article will review proximal iliotibial band syndrome, Morel-Lavallée lesions, external snapping hip syndrome, iliotibial band syndrome and bursitis, traumatic tears, iliotibial insertional tendinosis and peritendonitis, avulsion fractures at Gerdy's tubercle, and Segond fractures. The clinical management of these pathologies will also be discussed in brief.

The influence of platelet rich plasma on synovial fluid volumes, protein concentrations, and severity of pain in patients with knee osteoarthritis

Knee pain is commonly seen in orthopedic and rehabilitation outpatient clinical settings. Patients with knee osteoarthritis (OA) are often complicated with joint soreness, swelling, weakness, and pain. These complaints are often caused by the excessive amount of synovial fluid (SF) accumulated in the bursae around the knee joint. This study was aimed to evaluate the effectiveness of platelet rich plasma (PRP) in treating patients with minor to moderate knee osteoarthritis (OA) combined with supra-patellar bursitis using a proteomic approach and clinical evaluation tool. In this study, 24 elderly patients with minor to moderate knee OA combined with supra-patellar bursitis were recruited. Musculoskeletal ultrasound was used for accurate needle placement for the aspiration of SF followed by subsequent PRP injections. Three monthly PRP injections were performed to the affected knees for a total of 3months. Approximately after the 2nd PRP injection, significant decreases in SF total protein concentrations, volumes, and Lequesne index values were observed. SF proteins associated with chelation and anti-aging physiological functions such as matrilin, transthyretin, and complement 5 increased at least 2-fold in concentrations. Proteins associated with inflammation, such as apolipoprotein A-I, haptoglobin, immunoglobulin kappa chain, transferrin, and matrix metalloproteinase decreased at least 2-fold in concentrations. Therefore, at least two monthly PRP injections may be beneficial for treating patients with minor to moderate knee OA combined with supra-patellar bursitis.

Ultrasound evaluation of bursae: anatomy and pathological appearances

A bursa is an extra-articular sac that may communicate with a joint and functions to decrease friction between tendons and either bone or skin. Bursae can be classified as native and non-native (adventitious) bursae. The native bursae are lined with a synovial membrane and occur at predictable anatomical sites; knowledge of these normal structures can help distinguish them from other pathological entities. An adventitious bursa can form at sites of friction rather than at predictable anatomical sites, but otherwise have imaging features similar to native bursae. Bursal distention can occur from many pathological processes, most commonly resulting from chronic overuse injury. When imaging bursal pathological conditions, there is often an overlap of imaging findings, regardless of the cause. In general, ultrasound of a distended bursa reveals a fluid collection with either simple anechoic or more complex hypoechoic fluid. Bursal distention is characteristically unilocular and compressible, unlike other structures such as ganglion cysts, which are usually multilocular and non-compressible. This article reviews the anatomical locations of common bursae and shows pathological examples using ultrasound. Knowledge of typical locations and imaging appearances of bursae can aid in narrowing the differential diagnosis and guiding further management and treatment decisions.

Ganglion Cyst of Knee from Hoffa's Fat Pad Protruding Anterolaterally Through Retinacular Rent: A Case Report

Introduction:

Intra-articular ganglion cysts of the knee joint are rare occurrences. They are usually encountered as incidental findings in magnetic resonance imaging (MRI), or in arthroscopy. They may originate from both the cruciate ligaments and the menisci, from the popliteus tendon and alar folds, infrapatellar fat pad of Hoffa, and subchondral bone cysts. Those arising from the Hoffa’s fat pad, usually present as palpable mass at anterior aspect of the knee joint. We report a case of intraarticular ganglion cyst of knee arising from the infrapatellar fat pad and protruding anterolaterally through retinacular rent into the subcutaneous plane.

Case Report:

A 19-year-old young man, presented with a painless gradually increasing swelling at the anterior aspect of left knee of 9 months duration. MRI scan revealed a multilobulated, cyst with septations within the anterior aspect of the knee joint, just inferolateral to the patella, with deep extension into the infrapatellar fat pad, and superficial extension into the subcutaneous space across the retinaculum. After diagnostic arthroscopy, we performed an open excision of the cystic mass and confirmed the retinacular rent pre-operatively.

Conclusion:

Arthroscopic resection and debridement is the gold standard treatment in ganglion cyst of the knee. However, a subcutaneous extension may lead to incomplete arthroscopic resection: Leaving behind the residual tissue which may cause recurrence. Therefore, proper pre-operative evaluation of MR images of these cases is very important.

Spectrum of MRI features of ganglion and synovial cysts

Ganglion and synovial cysts occur mainly, but not necessarily, in association with osteoarthritis. Presentation varies widely, ranging from small, incidentally detected, asymptomatic lesions to giant ones that might be the source of symptoms, either due to their compressive effect on adjacent structures or due to complications, such as rupture. On magnetic resonance imaging they are typically presented as smooth, well-circumscribed, thin-walled, unilocular, and homogeneously T2-hyperintense lesions. An identifiable thin stalk communicating to the joint space is not infrequent. Nevertheless, depending on their age, anatomic location, and eventual complication, they might have many distinct appearances, including septae and internal debris, which the radiologist must be familiar with in order to accurately differentiate them from worrisome cystic-like lesions. With regard to this diversity, some illustrative cases are presented.

Traumatic Extra-capsular and Intra-capsular Floating Fat: Fat-fluid Levels of the Knee Revisited

Floating fat is a sign of acute bone injury at the knee following trauma. The goal of this article is to review the etiology, patterns, and mimickers of extra-capsular and intra-capsular floating fat, with the major emphasis on knee trauma in the acute setting. We will discuss the spectrum of multimodal imaging findings for rare presentations of extra-capsular floating fat, and contrast these with common and atypical forms of intra-capsular lipohemarthrosis, as an aid to the assessment of acute bone trauma at the knee.

Soft-tissue myxomatous lesions: review of salient imaging features with pathologic comparison

Myxoid soft-tissue lesions are a heterogeneous group of benign and malignant mesenchymal tumors with an abundance of extracellular mucoid material. These lesions may mimic cysts on radiologic evaluation because of the high water content, and histopathologic features also overlap. Benign myxoid lesions include intramuscular myxoma, synovial cyst, bursa, ganglion, and benign peripheral nerve sheath tumor, including neurofibroma and schwannoma. Malignant entities include myxoid liposarcoma, myxoid leiomyosarcoma, myxoid chondrosarcoma, ossifying fibromyxoid tumor, and myxofibrosarcoma. Some syndromes are associated with myxoid soft-tissue lesions, such as Mazabraud syndrome in patients with soft-tissue myxomas and fibrous dysplasia. Certain discriminating features, such as intralesional fat in a myxoid liposarcoma, perilesional edema and a rim of fat in soft-tissue myxoma, and the swirled T2-weighted signal intensity and enhancement pattern of aggressive angiomyxoma, assist the radiologist in differentiating these lesions. The presence of an internal chondroid matrix or incomplete peripheral ossification may suggest myxoid chondrosarcoma or ossifying fibromyxoid tumor, respectively. The entering-and-exiting-nerve sign is suggestive of a peripheral nerve sheath tumor. Communication with a joint or tendon sheath and peripheral enhancement may indicate a ganglion or synovial cyst. This article (a) reviews the magnetic resonance, computed tomographic, and ultrasonographic imaging characteristics of soft-tissue myxomatous lesions, emphasizing imaging findings that can help differentiate benign and malignant lesions; (b) presents differential diagnoses; and (c) provides pathologic correlation.

Radiological intervention of the hand and wrist

The role of radiological guided intervention is integral in the management of patients with musculoskeletal pathologies. The key to image-guided procedures is to achieve an accurately placed intervention with minimal invasion. This review article specifically concentrates on radiological procedures of the hand and wrist using ultrasound and fluoroscopic guidance. A systematic literature review of the most recent publications relevant to image-guided intervention of the hand and wrist was conducted. During this search, it became clear that there is little consensus regarding all aspects of image-guided intervention, from the technique adopted to the dosage of injectate and the specific drugs used. The aim of this article is to formulate an evidence-based reference point which can be utilized by radiologists and to describe the most commonly employed techniques.

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.

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.

Imaging of lumps and bumps in pediatric patients: an algorithm for appropriate imaging and pictorial review

Superficial lumps and bumps are a common presenting complaint in the pediatric patient population. Although encountered frequently, the path to a definitive diagnosis is not always a straightforward one. Imaging offers a valuable tool to aid in this diagnostic challenge. Radiologists must be familiar with pediatric lumps and bumps, their imaging characteristics, and the best way to further evaluate challenging clinical presentations. This will not only allow the radiologist to serve as a valuable asset to the treating physician in choosing the most appropriate imaging modality but also help in accurate diagnosis, all while ensuring the "image gently" principle. An algorithm for imaging in the pediatric patient with lumps and bumps has been presented in this article and a few example entities along with their imaging findings have also been reviewed.

An intra-articular ganglion cyst in a patient with juvenile idiopathic arthritis

We report an intra-articular ganglion cyst (IAGC) presenting as knee pain and a mass in a patient with longstanding Juvenile Idiopathic Arthritis (JIA). We could not find a similar case of an IAGC occurring in the knee of JIA patients in the literature. IAGC may need to be included as a possibility in patients with inflammatory arthritis with new-onset knee pain, especially in those with a palpable mass. MRI was useful in distinguishing IAGC from more worrisome causes of a knee mass. Orthopedic input was helpful in diagnosis and treatment. In addition, methotrexate therapy was effective in bringing about a long-lasting remission.

Tibial nerve intraneural ganglion cyst in a 10-year-old boy

Intraneural ganglion cysts are uncommon cystic lesions of peripheral nerves that are typically encountered in adults. In the lower extremity, the peroneal nerve is most frequently affected with involvement of the tibial nerve much less common. This article describes a tibial intraneural ganglion cyst in a 10-year-old boy. Although extremely rare, intraneural ganglion cysts of the tibial nerve should be considered when a nonenhancing cystic structure with intra-articular extension is identified along the course of the nerve. This report also details the unsuccessful attempt at percutaneous treatment with US-guided cyst aspiration and steroid injection, an option recently reported as a viable alternative to open surgical resection.

Synovial cyst of the antecubital fossa mimicking a brachial artery pseudoaneurysm: report of a case

Pseudoaneurysms of the brachial artery are common following a percutaneous cardiac catheterization. Synovial cysts are a commonly identified entity in patients with rheumatic diseases as well. We present a rare case of a synovial cyst in the elbow masquerading as an iatrogenic pseudoaneurysm of the brachial artery. A 51-year-old female patient presented with a pulsatile and painful mass in the right antecubital fossa. The medical history revealed a recent diagnostic cardiac catheterization at the same site and rheumatoid arthritis under oral treatment. Imaging investigations were not fully diagnostic. Because of the clinical suspicion of a thrombosed pseudoaneurysm, exploratory surgery was indicated. The pathologic examination of the specimen confirmed the diagnosis of a synovial cyst. Ultrasonography and computed tomography imaging are valuable in the everyday clinical practice but they do not always exclude an iatrogenic pseudoaneurysm, especially when the medical history is suspicious. Surgical removal is the proper treatment and pathologic examination sets the final diagnosis in such cases of diagnostic difficulty.

Value of ultrasound before joint aspiration

OBJECTIVE

The purpose of this article is to illustrate and discuss the value of ultra-sound screening before joint aspiration.

CONCLUSION

Before joint aspiration, ultrasound assessment of the overlying and surrounding soft tissues requires little time and is relatively inexpensive. Bursal fluid collections, soft-tissue abscesses, and other fluid collections that would be undetected with fluoroscopy or blind aspiration can thus be identified. Ultrasound screening before joint aspiration can aid diagnosis and decrease the risk of iatrogenic complications.

"Cystic"-appearing soft tissue masses: what is the role of anatomic, functional, and metabolic MR imaging techniques in their characterization?

Although conventional MR imaging with contrast-enhanced T1-weighted sequences is of paramount importance for evaluating soft tissue masses, noncontrast MR sequences have emerged that facilitate their characterization. In this article, the utility and pitfalls of conventional MR imaging with T1-weighted, fluid-sensitive, and contrast-enhanced sequences will be discussed, along with that of functional (diffusion weighted imaging) and metabolic (proton MR spectroscopy) non-contrast-enhanced techniques for the purpose of soft tissue mass characterization. In particular, we discuss the application of these techniques to differentiating neoplastic or inflammatory masses that have high fluid content from benign cysts, as this distinction is a common pitfall of conventional sequences.

A ganglion of the patellar tendon in patellar tendon-lateral femoral condyle friction syndrome

Intratendinous ganglia are rare. We report the case of a sedentary woman with chronic mechanical anterolateral pain of the knee and an extensive ganglion of the patellar tendon as indicated on magnetic resonance (MR) and ultrasound (US) examinations. There was evidence of a high-riding patella, patellar malalignment and patellar tendon-lateral femoral condyle friction syndrome with significantly close contact between the patellar tendon and the lateral facet of the femoral trochlea. The ultrasound-guided aspiration of the ganglion enabled a localized injection of an anti-inflammatory drug (cortivazol) and the cytopathological examination of the fluid, which confirmed the diagnosis. Clinical improvement was maintained with knee rehabilitation and was satisfactory at follow-up after 1 year. To our knowledge, we report the first case of a ganglion of the patellar tendon subsequent to patellar tendon-lateral femoral condyle friction syndrome. We found that this case was illustrative of mucoid degeneration in connective tissue due to chronic repetitive microtraumas. Additionally, this case provided the opportunity to discuss the management of this condition in a sedentary individual with a high-riding patella and patellar malalignment.

MRI characteristics of cysts and "cyst-like" lesions in and around the knee: what the radiologist needs to know

Objectives and Methods

A variety of benign cystic or “cyst-like” lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee. These lesions comprise a diverse group of entities from benign cysts to complications of underlying diseases. In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended. However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

Results

This article includes a comprehensive pictorial essay of the characteristic MRI features of common and uncommon benign cysts and “cyst-like” lesions in and around the knee joint.

Discussion

For accurate assessment of the “cystic structure”, a radiologist should be able to identify typical MRI patterns that contribute in establishing the correct diagnosis and thus guiding specific therapy and avoiding unwarranted interventional procedures such as biopsy or arthroscopy.

Teaching points

• Cystic lesions are common in knee MRI and the commonest, the Baker’s cyst, has an incidence of 38 %.

• Synovial cysts, meniscal cysts, normal knee bursae and recesses have characteristic MR appearances.

• Miscellaneous “cyst-like” lesions may require a more dedicated MR protocol for a correct diagnosis.

Arthroscopic decompression of suprapatellar cyst: case report

Bursae around the knee reduce friction between moving structures. When involution of suprapatellar septum fails to occur ("complete septum"), then suprapatellar bursa may stay completely separated from the knee joint cavity to form a cystic cavity. In the case of the increased volume, suprapatellar bursitis can cause painful suprapatellar swelling. The aim is to point to the possibility of arthroscopic decompression of suprapatellar cyst. In the case presented, the indication for knee arthroscopy was based on clinical examination, ultrasonography and magnetic resonance studies. The preoperative diagnosis was verified intra-operatively, and intra-articular cyst decompression was performed by arthroscopy. At the final examination 8 months postoperatively, the patient still had no pain, swelling and had full range of motion. This minimally invasive operative procedure resulted in a satisfactory anatomic and functional outcome. In this case report, we present a patient with suprapatellar cyst submitted to arthroscopic cyst decompression.

Symptomatic ganglion cyst of the popliteus tendon treated with ultrasound-guided aspiration and steroid injection: a case report

Ultrasound-guided aspiration of symptomatic ganglion cysts about peripheral joints is a valuable and routinely performed therapeutic modality. Intratendinous and peritendinous ganglia involving the popliteus tendon are rare, with only 3 cases previously reported. These ganglion cysts are usually small and can easily be mistaken for normal anatomy on magnetic resonance imaging (ie, small periarticular vessel or fluid within the popliteus tendon sheath), leading to delayed patient diagnosis and appropriate treatment.

Normal MR imaging anatomy of the knee

Magnetic resonance (MR) imaging is the preferred imaging modality for evaluating internal derangement of the knee, due to its superior soft tissue contrast resolution, multiplanar imaging capability, and lack of ionizing radiation. The superb image quality facilitates learning of normal imaging anatomy and conceptualizing spatial relationships of anatomic structures, leading to improved understanding of pathologic processes, mechanisms of injury, and injury patterns, and ultimately increased diagnostic accuracy. This article depicts normal MR imaging anatomy and commonly encountered anatomic variants using representative MR images of the knee, and describes and explains the rationale of routine knee MR imaging protocol.

Large intra-articular anterior cruciate ligament ganglion cyst, presenting with inability to flex the knee

A 41-year-old female presented with a 3-month history of gradually worsening anterior knee pain, swelling and inability to flex the knee. Magnetic resonance imaging (MRI) revealed a large intra-articular cystic swelling anterior to the anterior cruciate ligament (ACL), extending into the Hoffa's infrapatellar fat pad. Following manipulation under anaesthesia and arthroscopic debridement of the cyst, the patient's symptoms were relieved with restoration of normal knee motion. ACL ganglion cysts are uncommon intra-articular pathological entities, which are usually asymptomatic and diagnosed incidentally by MRI. This is the first reported case of an ACL cyst being so large as to cause a mechanical block to knee flexion.

Posterior knee pain

Posterior knee pain is a common patient complaint. There are broad differential diagnoses of posterior knee pain ranging from common causes such as injury to the musculotendinous structures to less common causes such as osteochondroma. A precise understanding of knee anatomy, the physical examination, and of the differential diagnosis is needed to accurately evaluate and treat posterior knee pain. This article provides a review of the anatomy and important aspects of the history and physical examination when evaluating posterior knee pain. It concludes by discussing the causes and management of posterior knee pain.

Juxta-articular myxoma of the knee in a 5-year-old boy: a case report and review of the literature (2009: 12b)

Juxta-articular myxoma (JAM) is a relatively rare variant of myxoma that occurs in the vicinity of large joints. It is composed of fibroblast-like cells that produce an excessive amount of glycosaminoglycans rich in hyaluronic acid. The peak incidence is between the 3rd and 5th decades of life. In this report we describe an extremely rare case of JAM in the knee of a 5-year-old child. The clinical presentation, radiological features and histopathologic findings are described, and the relevant literature is reviewed.