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

Effectiveness of capsulodesis in ganglion cysts caused by a medial meniscotibial ligament tear and medial meniscus extrusion

INTRODUCTION AND IMPORTANCE

Meniscotibial ligament (MTL) has received attention as a major meniscus stabilizer. An MTL injury results in instability and extrusion of the meniscus. Cases of knee ganglion cyst formation due to an MTL tear and medial meniscus extrusion (ME) are extremely rare.

CASE PRESENTATION

A 42-year-old female Japanese childcare worker presented painful ganglion cysts on the proximal medial side of her left tibia. An MTL tear and medial ME were thought to be involved in the ganglion formation. Joint fluid flowed through the meniscotibial side of the extruded meniscus into the space between the medial collateral ligament and tibia, where the MTL tear acted as a check valve, forming ganglion cysts. Ultrasonography-guided aspiration of the ganglion was attempted, but ganglion cysts recurred within 1 month. We used an open excision for the ganglion cysts, and arthroscopic capsulodesis was performed to repair the MTL and internalize the medial meniscus to block the inflow route from the intra-articular space.

CLINICAL DISCUSSION

We performed capsulodesis, which repaired the MTL and internalized the medial meniscus to prevent the recurrence of the ganglion cyst. Three months have passed since the surgery, with no recurrence of knee pain or ganglion cysts, indicating good short-term results.

CONCLUSIONS

We encountered a rare case of ganglion cyst formation in the knee joint due to MTL tear and medial ME. Arthroscopic MTL repair and internalization of the meniscus by capsulodesis were effective in treating the ganglion cysts.

Interosseous ganglion cyst of the ribs with unusual presentation of hemoptysis

An interosseous ganglion cyst is a very rare entity, found mostly in skeletally mature patients, particularly in long bones such as the tibia and femur. However, we are the first to report here an unusual case of interosseous ganglion cyst of the upper ribs in a young female patient, which she had an unpredicted presentation of cough and hemoptysis and a large painful lump over the anterior left upper chest. The radiological and pathological workup confirmed the presence of a benign interosseous ganglion cyst arising from the left first rib, invading the second rib and the apex of the left lung. The patient has been treated successfully by surgical resection of this rib cyst. However, we could not find any reported cases in the current literature of an interosseous ganglion cyst pathology arising in the ribs with a similar presentation of cough and hemoptysis.

Demystifying the "Dark Side of the Knee": An Update on Imaging of the Posterolateral Corner

The posterolateral corner (PLC) of the knee is a complex anatomical-functional unit that includes ligamentous and tendinous structures that are crucial for joint stability. This review discusses the intricate anatomy, biomechanics, and imaging modalities, as well as the current challenges in diagnosing PLC injuries, with an emphasis on magnetic resonance imaging (MRI). Recognizing the normal MRI anatomy is critical in identifying abnormalities and guiding effective treatment strategies. Identification of the smaller structures of the PLC, traditionally difficult to depict on imaging, may not be necessary to diagnose a clinically significant PLC injury. Injuries to the PLC, often associated with cruciate ligament tears, should be promptly identified because failure to recognize them may result in persistent instability, secondary osteoarthritis, and cruciate graft failure.

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.

Evaluation of the relationship between Knee Osteoarthritis and Meniscus Pathologies

Background

Knee osteoarthritis is a common, degenerative joint disease that causes chronic pain that affects daily life. Our study aims to evaluate geriatric patients aged 65 and over with knee pain in terms of osteoarthritis with radiography and magnetic resonance imaging and to investigate its relationship with meniscal pathologies.

Methods

Radiography and magnetic resonance imaging of patients aged 65-88 years with knee pain were evaluated in terms of knee osteoarthritis and staging was performed. Meniscal pathologies were evaluated in magnetic resonance imaging, and the prevalence of different meniscal lesion types was calculated. In addition, the relationship between knee osteoarthritis and meniscal pathologies was analyzed.

Results

Radiographic evidence of knee osteoarthritis was found in 182 (84.2%) of the 216 cases in our study group. A strong correlation was found between the degrees of knee osteoarthritis on magnetic resonance imaging and radiography. At least one meniscus pathology was observed in all 182 radiography cases with knee osteoarthritis findings. At least one meniscus pathology was observed in 29 (85.3%) of those without osteoarthritis signs. It was determined that meniscus degeneration, tear, and extrusion were observed more frequently in patients with knee osteoarthritis than in patients without osteoarthritis. Meniscal extrusion and complex and horizontaltype tears were the most common lesions.

Conclusions

Osteoarthritis was found to be common in geriatric patients with knee pain. A correlation was found between radiography and magnetic resonance imaging regarding knee osteoarthritis. It was observed that meniscal pathologies were detected more frequently in patients with knee osteoarthritis.

An Unusually Massive Hemorrhagic Superficial Infrapatellar Bursa Excised in a One-stage Procedure: Case Report

Introduction

Superficial infrapatellar bursitis may be traumatic, inflammatory, or infectious. It rarely attains massive dimensions. Open excision can be performed as a one-stage or a two-stage procedure, and endoscopy can be an alternative. We report a chronic, unusually massive, hemorrhagic infrapatellar bursa which we resected totally in a single stage procedure with no significant complications.

Case Report

A 65-year-old male farmer presented with a chronic massive swelling in front of the right knee which first appeared 4 years earlier and had no effect on his general condition. The mass was excised in a one-stage procedure and it was found to be a hemorrhagic bursitis. The wound healed uneventfully and, on follow-up 7 weeks later, the patient was able to perform full flexion and extension of the knee.

Conclusion

Two-stage procedures for excision are effective, but one-stage procedures are equally effective in chronic cases, provided the dissection is performed meticulously and atraumatically.

Ganglionic Cyst of Periosteal Origin Mimicking as Pes Anserine Bursitis - A Rare Entity and Literature Review

Introduction

Periosteal ganglion is a form of cystic swelling commonly seen around long bones of lower extremities.

Case Report

A 55-year-old male presented to outdoor clinic with gradually increasing swelling around anteromedial aspect of the right knee joint with intermittent pain on prolonged standing and walking for 8 months. Magnetic resonance imaging was suggestive of ganglionic cyst which was confirmed later by histopathological examination.

Conclusion

Ganglionic cyst of periosteal origin is a rare entity. Complete excision is the recommended treatment option; if not performed appropriately chances of recurrence are high.

Intra-Articular Ganglion Cysts of the Knee

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Magnetic resonance imaging (MRI) without contrast is sufficient to diagnose an intra-articular ganglion cyst of the knee. MRI with intravenous contrast may be considered for cysts in the infrapatellar fat pad, which are not a typical presentation.

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The current literature supports treating symptomatic cases or those discovered accidently during knee arthroscopy with arthroscopic excision.

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Although aspiration of these cysts results in a higher recurrence rate than excision, it is associated with quicker recovery. Thus, aspiration might be chosen as an initial treatment for anyone who would like to avoid surgery or requires a rapid recovery, including professional athletes.

➢

Open excision may be considered for infrapatellar fat pad cysts that are >4.5 cm in size.

Automated detection of knee cystic lesions on magnetic resonance imaging using deep learning

Background

Cystic lesions are frequently observed in knee joint diseases and are usually associated with joint pain, degenerative disorders, or acute injury. Magnetic resonance imaging-based, artificial intelligence-assisted cyst detection is an effective method to improve the whole knee joint analysis. However, few studies have investigated this method. This study is the first attempt at auto-detection of knee cysts based on deep learning methods.

Methods

This retrospective study collected data from 282 subjects with knee cysts confirmed at our institution from January to October 2021. A Squeeze-and-Excitation (SE) inception attention-based You only look once version 5 (SE-YOLOv5) model was developed based on a self-attention mechanism for knee cyst-like lesion detection and differentiation from knee effusions, both characterized by high T2-weighted signals in magnetic resonance imaging (MRI) scans. Model performance was evaluated via metrics including accuracy, precision, recall, mean average precision (mAP), F1 score, and frames per second (fps).

Results

The deep learning model could accurately identify knee MRI scans and auto-detect both obvious cyst lesions and small ones with inconspicuous contrasts. The SE-YOLO V5 model constructed in this study yielded superior performance (F1 = 0.879, precision = 0.887, recall = 0.872, all class mAP0.5 = 0.944, effusion mAP = 0.945, cyst mAP = 0.942) and improved detection speed compared to a traditional YOLO model.

Conclusion

This proof-of-concept study examined whether deep learning models could detect knee cysts and distinguish them from knee effusions. The results demonstrated that the classical Yolo V5 and proposed SE-Yolo V5 models could accurately identify cysts.

A Rare Presentation of a True Intra-articular Lipoma: A Case Report and Review of Imaging Findings

This report describes the unique case of an intra-articular lipoma in a 34-year-old male. The patient presented with a history of chronic knee pain associated with an intermittent sensation of the knee giving way. Physical examination and initial radiographic imaging were unremarkable. Magnetic resonance imaging (MRI) revealed a 9.2 x 6.7 mm ovoid mass posterior to the posterior cruciate ligament (PCL) exhibiting hyperintense signals on T1-weighted images and intermediate-to-high intensity signals on T2. On subsequent proton density fat suppression sequences, the mass demonstrated homogenous signal suppression and was confirmed as being a lipoma. To the best of our knowledge, this is only the second reported case of an intra-articular lipoma arising posterior to the PCL. Intra-articular lipomas, albeit rare, should be considered in the differential diagnosis for chronic knee pain with associated joint motion abnormalities. MRI remains the gold standard in imaging intra-articular soft tissue pathology and should be the study of choice in differentiating intra-articular lipomas from similar conditions such as pigmented villonodular synovitis and lipoma arborescens.

Giant intraosseous ganglion of the fibula: multimodality imaging

Intraosseous ganglia around the knee are most commonly located in the proximal tibia and limited to the epiphyseal-metaphyseal region. We report the case of a giant intraosseous ganglion of the fibula. MRI demonstrated the fluid avascular content of the lesion. CT arthrography of the knee demonstrated partial opacification of the lesion through a cortical bone defect. The lesion was treated with curettage and bone grafting. Anatomopathological examination confirmed the medical imaging diagnosis of intraosseous ganglion. This case highlights the value of joint opacification with CT arthrography to demonstrate the communication between the articular cavity and the ganglion.

Sonography of Knee Effusion

Objective:

A review of the anatomy of the synovial recesses of the knee is important to better understand the different effusion presentations, update the diagnosis criteria of knee effusion based on the measured synovial recesses and discuss the differentiation of some effused recesses from other lesions around the knee.

Method:

This review focuses on the anatomy of the synovial recesses of the knee and classifies them into three groups (anterior, parameniscal, and posterior recesses), as well as provides an overview on the etiology of knee effusion, its sonographic detection, and diagnosis criteria.

Results:

Knee effusion is a very common pathological finding in sonography of the knee. The unique joint structure of the knee provides the possibility to host complex synovial recesses. Fluid in some of the synovial recesses is valuable for the diagnosis of knee effusion, while in certain situations, some recesses may impose diagnostic uncertainty. Knowledge of these synovial recesses is essential to avoid diagnostic pitfalls.

Conclusion:

This review provides an important discussion of the differentiation of some recesses effusions from other lesions around the knee.

Surgical Approach to Pigmented Villonodular Synovitis and Synovial Osteochondromatosis in Pathological Expansion of the Popliteus Bursa

We orthopaedic surgeons are not familiar with the popliteus bursa. It is defined as the expansion in the synovial membrane of the posterolateral part of the knee that lies between the lateral meniscus and the tendon of the popliteus muscle. The popliteus bursa extends approximately 1 cm distal to the joint line and has 4 borders; the medial border is the peripheral margin of the lateral meniscus, the lateral border is the popliteus tendon, and the superior and inferior borders are formed by 2 fascicles. We very rarely observe cystic lesions that expand more distally, such as pigmented villonodular synovitis (PVNS) and synovial osteochondromatosis. We consider the distally expanded bursa as the pathologic expansion of the popliteus bursa. When this expansion is involved with PVNS, it may be the cause of recurrence of PVNS in the knee joint. Synovial osteochondromatosis in this expansion may cause pain in the posterolateral corner of the knee and may become a source of free bodies in the knee joint. In such conditions, these lesions should be surgically excised. The purpose of this Technical Note is to describe a surgical approach to the pathologic expansion of the popliteus bursa.

Sonographic assessment of the anatomy and common pathologies of clinically important bursae

High-resolution ultrasonography has many advantages in the imaging of the musculoskeletal system, when compared to other imaging methods, particularly in superficial, easily accessible parts of the body. It is a perfect diagnostic tool for visualizing the most common pathologies of the musculoskeletal system, including the bursae. Inflammation of bursae is frequent, and it can mimic other diseases of the musculoskeletal system. Therefore, knowledge of normal ultrasound anatomy of the bursae, their exact location in the human body, and the sonographic signs of their most common pathologies is essential for establishing a quick and accurate diagnosis by ultrasound. Common conditions affecting bursae, leading to bursitis, include acute trauma, overuse syndromes, degenerative diseases, inflammatory conditions (rheumatoid arthritis, psoriatic arthritis, gout etc.), infections such as tuberculosis, synovial tumors and tumor-like conditions (pigmented villonodular synovitis, osteochondromatosis), and many more. This review article presents and explains ultrasound examples of the most frequent pathological conditions affecting bursae. Images include normal and pathological conditions of bursae around the shoulder joint, elbow, hip, knee, and ankle joint.

Possible case of pressure resorption associated with osteoarthritis in human skeletal remains from ancient China

Osteoarthritis, one of the most common pathological conditions observed in human skeletal remains, is traditionally thought to only affect the structures within the joint capsule. We examined the osteoarthritic distal femora of an individual from Ancient North China, ca. 475-221 BCE. The standard signs of osteoarthritis, marginal lipping and extensive eburnation, were observed in the patellofemoral compartment of the knee joint. In addition however were bilateral pressure-caused fossae on the extra-articular anterior surfaces of the distal femora 10 mm proximal to the large osteophytes at the apex of the patellar surfaces. Anatomy and possible pathogenesis of knee arthritis are explored in order to come to a tentative aetiology of the extra-articular lesions. These lesions are suggested to be a new criterion for identifying severe knee arthritis. The osteological phenomenon is then placed into archaeological context of the Warring States period of ancient China.

A circular depression at the spinoglenoid notch of a prehistoric Andean scapula: Plausible evidence of suprascapular nerve entrapment by a paralabral cyst

While intraosseous cysts have been described in the paleopathological literature, it is rare to find reports concerning effects of soft tissue cysts, although they are relatively common in clinical contexts. Here we present plausible evidence of an extraosseous paralabral cyst, seen in an adult scapula from a Late Intermediate period commingled tomb (ca. AD 1200) at the northern highland site of Marcajirca, Ancash, Peru. The scapula demonstrated a smooth-sided concave depression at the spinoglenoid notch. The depression was notable for its regular appearance, with no bone deposition or destruction. Rather than reflect an intraosseous pathology, the defect likely resulted from pressure erosion from a space-occupying mass. A narrow strip of flattened bone connected the depression to the posterior-superior aspect of the glenoid. The location and morphology of the depression and its connection with the glenoid are consistent with the effects of a paralabral cyst that arose secondary to a tear of the posterior-superior glenoid labrum. A labral tear may act as a one-way valve permitting fluid to flow along a path of least resistance, often to the spinoglenoid notch. A cyst at the spinoglenoid notch would compress the suprascapular nerve, causing weakened function of infraspinatus and its eventual atrophy.

A case report on rare occurrence of periosteal ganglion cyst in femoral intercondylar region

Ganglions are the cysts derived from myxomatous degeneration of periarticular tissue, commonly found around wrist and foot. Ganglion cysts are uncommon in Knee region and if present their occurrence is mostly incidental and benign. Based on their location, this could be extraarticular or intraarticular. Lesions with similar pathology in subchondral region around joints are lesser common entity called Intraosseous ganglions. Rarer still is the lesion produced by myxomatous degeneration of periosteum of long bone, called periosteal ganglion. We here present a case of 35 year old Male with gradual onset, poorly localised pain behind left knee which was radiologically suggestive of periosteal ganglion, eroding the posterior aspect of femur and confirmed histopathologically following the excision of a lesion from posterior aspect of femoral condyles.

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 prevalence and characteristics of a subcortical cystic lesion at the subspinous region of the knee

Background Although we observed that subcortical cysts near the attachment of the meniscus or cruciate ligaments are frequently seen with a tear or degeneration of the adjacent meniscus and/or cruciate ligament, there is no large study describing the prevalence, distribution, and associated findings of these cysts. Purpose To evaluate the prevalence and distribution of subcortical cysts near the attachments of the meniscus or cruciate ligaments and evaluate pathologies of the meniscus or cruciate ligaments using magnetic resonance imaging (MRI). Material and Methods We reviewed 1009 knee MRIs for the presence of subcortical cysts near the meniscus or cruciate ligament attachments and evaluated their size, location, edema of the adjacent bone marrow, and integrities of the medial and lateral meniscus and anterior and posterior cruciate ligaments. Results The 110 cysts were found in either the middle (n = 56), posterior (n = 52), or anterior (n = 2) subspinous regions. Sixty-two were at meniscal root insertion, including seven at the lateral meniscus anterior horn, five at the lateral meniscus posterior horn, 48 at the medial meniscus posterior horn, and two at the medial meniscus anterior horn. All were associated with an adjacent meniscal pathology. Of the 34 cysts at the anterior cruciate ligament (ACL) insertion, 28 had ACL pathology. Nine cysts had surrounding edema in the adjacent bone marrow. Conclusion Subcortical cysts at the subspinous region of the knee were seen in 9.6% of knee MRI examinations. Most were in close proximity to the meniscal or cruciate ligaments with associated pathologies, suggesting that abnormal stress on the bone induces cyst formation.

Soft tissue pseudotumours: a pictorial review with emphasis on MRI

Background

Several tumour-like conditions of the soft tissues may be encountered in clinical practice, or when patients undergo radiologic examinations. Al-though advances in cross sectional imaging (ultra-sound, MDCT and MRI) play a pivotal role in the correct evaluation of tumour-like lesions, a systematic approach is needed to achieve a definitive diagnosis or limit the differential diagnosis. Clinical history, physical examination and anatomic location are of paramount importance.

Methods

In this pictorial essay we review some of the most frequent benign soft tissue conditions which may be mistaken for malignancy and thus lead to need-less referrals, unnecessary biopsies and great anxiety to the patients and their carers.

Level of evidence

IV.

Anatomical and radiological evaluation of less invasive stabilisation system (LISS) in correlation with knee lateral collateral ligament insertion

INTRODUCTION

The Less Invasive Stabilisation System (LISS) is an angle-stable plate that enables treatment of distal femoral comminuted and periprosthetic fracture. As it is placed through a minimally-invasive lateral approach, lateral knee pain is a commonly described symptom after its application. This study investigates knee lateral collateral ligament (LCL) iatrogenic injury during LISS plate fixation. A cadaver study was performed and a retrospective radiological investigation with the analysis of its clinical application was conducted to evaluate possible knee LCL damage.

METHODS

The cadaver study included 13 human lower extremities, treated with LISS. After application, lateral knee side was dissected, implants were removed and distances between the drill holes and LCL origin were measured. In the retrospective radiological evaluation, postoperative X-rays for patients treated with distal femoral LISS plate in the University Hospital Regensburg, Germany from January 2010 to December 2015 were examined. Following a protocol described by Pietrini et al., the LCL origin on postoperative X-rays was calculated, both in lateral and anterior-posterior (AP) view, and distances between the plate and its closest locking screw to the LCL origin were measured.

RESULTS

In the cadaver study, the mean distance between the closest drilling hole and the ligament origin was 14.0mm (range 9-21mm; SD 3.8mm). Twenty-two patients matched the inclusion criteria for the retrospective radiological study. In lateral view, the mean distance between the origin and the closest locking screw was 6.3mm (range 0-16.4mm; SD 4.7mm); the mean distance between the origin and the plate was 3.1mm (range 0-13.9mm; SD 4.1mm). In AP view, the mean distance between LCL origin and the nearest screw was 2.4mm (range 0-7.6mm; SD 2.4mm). The mean distance between the origin and the most distal locking screw was 9.2mm (range 0-17.5mm; SD 4.0mm).

DISCUSSION

The LISS is a safe option to treat distal femoral fractures in respect to the LCL. Due to close proximity, the LCL might be harmed; therefore, lateral knee pain or lateral instability after implantation should be assessed in further treatment.

Magnetic resonance imaging of painful swollen legs in the emergency department: a pictorial essay

Patients presenting with a painful swollen leg are not infrequently encountered at the emergency department and can pose a diagnostic dilemma for attending physicians. The potential causes of leg pain and swelling include trauma, infection, inflammation, and neurogenic, vascular, and iatrogenic conditions; with magnetic resonance imaging (MRI) being an important tool in evaluation. We describe the MRI features of various conditions causing painful swollen legs. We also discuss the differential diagnosis and the useful clinical and laboratory findings that radiologists should be aware of, in order to arrive at an accurate diagnosis.

Distension of the Medial Collateral Ligament Bursa of the Knee With Possible Bursitis

The bursitis of the medial collateral ligament (MCL) of the knee is the inflammatory distension of the bursa located between the superficial and deep portions of MCL. Five cases with sonographic findings of suspected MCL bursitis were reviewed. All five cases had fluid collection with distinct and smooth borders between the superficial and deep portions of the MCL. Two of them had the fluid adjacent to the tibia; two of them adjacent to the femur; and one of them spanning the joint. Four of the five patients without recognizable knee injury history and middle third meniscal tear excluded the possibility of injury-related fluid collection. Hence, MCL bursitis is the possible diagnosis. One young adult with a recent knee injury also had a tear in the meniscofemoral ligament of the deep portion of the MCL. The distension of the bursa was interrupted by and directly connected to the tear of the meniscofemoral ligament. Therefore, it is part of the injury but not bursitis. This report describes sonographic characteristics of MCL bursitis that may assist in the diagnosis and differentiate it from other medial knee conditions.

Ultrasound-guided percutaneous lavage of calcific bursitis of the medial collateral ligament of the knee: a case report and review of the literature

OBJECTIVES

Calcification of the medial collateral ligament (MCL) of the knee is rare. The literature reports no positive outcomes when conservative treatment has been followed. This paper reports a case of such calcification and its treatment using ultrasound-guided percutaneous lavage (UGPL).

METHODS

A 66-year-old patient presented with medial knee pain. X-ray, ultrasound, and magnetic resonance (MR) examinations revealed calcific bursitis of the MCL, which was treated by UGPL.

RESULTS

One month after treatment the patient was asymptomatic. X-ray, ultrasound, and MR examinations confirmed the almost complete disappearance of the calcification; only very tiny fragments remained.

CONCLUSIONS

Calcific bursitis of the MCL of the knee is very uncommon, but should be taken into account in differential diagnoses for medial knee pain. UGPL is proposed as a treatment for this condition.

Magnetic resonance imaging of Hoffa's fat pad and relevance for osteoarthritis research: a narrative review

OBJECTIVE

To give an illustrative overview of Hoffa's fat pad pathology with a radiologic emphasis on the anatomy, on technical considerations, and on imaging differential diagnoses in the context of osteoarthritis (OA) imaging research.

DESIGN

A PubMed database search including only English literature and covering a 20 year period was performed. The search was based on but no limited to the query terms "Hoffa", "Hoffa's fat pad" or "infrapatellar fat pad (IPFP)" in combination with "synovitis", "OA", and "magnetic resonance imaging (MRI)". The literature search yielded 289 publications that were screened for relevance; additional references were included when these were considered of importance.

RESULTS

Several anatomic variants and pathologic conditions may be encountered when assessing Hoffa's fat pad including tumors and tumor-like lesions such as osteochondroma, tenosynovial giant cell tumor (TGCT) (and pigmented nodular synovitis) and arthrofibrosis, traumatic changes including contusions and anatomic variants such as recesses. The latter may be accountable for differences in cross-sectional area or volume changes over time. Signal changes are commonly used in OA research as surrogate markers for synovitis but are non-specific findings.

CONCLUSIONS

Quantitative approaches to evaluate 3D parameters of Hoffa's fat pad are increasingly applied and their role in regard to structural progression and clinical manifestations of disease needs to be further elucidated. In applying such approaches, knowledge of the detailed anatomy and potential pitfalls that may be a result of anatomical variants, inflammatory disease manifestations and additional diverse pathologies encountered seems to be paramount.

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.

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.

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.