Monoarticular synovial lesions: radiologic pictorial essay with pathologic illustration

Pediatric solid intra-articular masses of the knee: prevalence, imaging features and etiologies

BACKGROUND

The etiologies of pediatric solid intra-articular soft-tissue masses are not well described and can present diagnostic dilemmas.

OBJECTIVE

Our hypothesis was that these entities have a limited differential diagnosis and are mostly benign.

MATERIALS AND METHODS

We reviewed knee magnetic resonance imaging (MRI) scans performed at our tertiary care institution between 2001 and 2019 (n=3,915). Our inclusion criterion was knee MRI with a solid intra-articular soft-tissue mass. Our exclusion criteria were cases with no masses or non-solid intra-articular lesions with clear radiologic diagnoses. Multiple radiologic characteristics were evaluated. Radiologic and histological diagnoses were collected when available. Cases without histology were assigned a suspected diagnosis.

RESULTS

Twenty-five out of 3,915 (<1%) cases met the inclusion/exclusion criteria. Twenty patients underwent biopsy. Patient age ranged from 1 to 19 years with a mean age of 12 years. Lesion size ranged from 1 to 7 cm with a mean of 3.3 cm. The top three histological diagnoses were pigmented villonodular synovitis (PVNS) (7/20, 35%), vascular malformations (2/20, 10%) and inflammatory arthritis (2/20, 10%). There was one malignant case of synovial sarcoma (1/20, 5%). Of the five cases without biopsies, PVNS was the most common diagnosis (3/5, 60%). Five out of 10 (50%) PVNS cases were focal and 5/10 (50%) were multifocal. All PVNS cases (10/10, 100%) had hypointense signal on T2.

CONCLUSION

Solid intra-articular soft-tissue masses of the knee in children are rare, with a prevalence of <1% in our study. The vast majority are benign with PVNS being the most common diagnosis.

Synovial Chondromatosis Surrounding the First Metatarsophalangeal Joint: A Case Report

Synovial chondromatosis is a benign synovial tumor that rarely occurs in the foot. We present a case of a 36-year-old male who underwent surgical excision of primary synovial chondromatosis of the first metatarsophalangeal joint. This report also presents a review of the literature related to synovial chondromatosis of the foot. Currently in the literature, this pathology has been described as occurring in multiple locations in the foot and ankle. Synovial chondromatosis can occur primarily or secondarily in diseased joints. Treatment is based on the phase of disease, with a goal to decrease pain and arthritis, and increase mobility. Surgical techniques used for foot and ankle synovial chondromatosis have been adapted from larger joints where the condition is more prevalent. Further case studies are needed to formulate a treatment protocol for foot and ankle synovial chondromatosis, but successful surgical excision was found in this case report.

LEVELS OF EVIDENCE

Therapeutic, Level IV: Case study.

Synovial Chondromatosis of the Ankle Joint: Clinical, Radiological, and Intraoperative Findings

Synovial chondromatosis, also termed synovial osteochondromatosis, is a rare benign disorder characterized by the presence of cartilaginous nodules in the synovium of the joints, tendon sheaths, and bursae. It most commonly involves large joints, such as the knee, hip, and shoulder, but its presence in smaller joints has also been reported. Nevertheless, ankle involvement is unusual. The diagnosis is commonly made following a thorough history, clinical, physical, and radiographic examination. We report a case of a young patient with primary synovial chondromatosis of the ankle joint and present the clinical, radiographic, and intraoperative findings.

Pediatric soft-tissue tumors and pseudotumors: MR imaging features with pathologic correlation: part 2. Tumors of fibroblastic/myofibroblastic, so-called fibrohistiocytic, muscular, lymphomatous, neurogenic, hair matrix, and uncertain origin

In the final part of this two-part review article on soft-tissue masses in children, the magnetic resonance (MR) imaging features, clinical findings, and pathologic findings in a wide variety of tumors, including those of fibroblastic/myofibroblastic origin, so-called fibrohistiocytic tumors, smooth-muscle tumors, skeletal-muscle tumors, tumors of uncertain differentiation, and lymphoma, are described. Other neoplasms that are not included in the World Health Organization classification of soft-tissue tumors but may be seen clinically as soft-tissue masses, specifically dermatofibrosarcoma protuberans, neurogenic tumors and pilomatricoma, are also included. In contrast to the tumors reviewed in Part 1 of this review, the MR imaging features and clinical findings of the tumors included here are largely nonspecific. However, MR imaging is useful in determining site of tumor origin, extent of disease, and relation of tumor to adjacent anatomic structures, and for follow-up after therapy. In some of these entities, the combination of findings may aid in narrowing the differential diagnosis, such as persistent low signal intensity on T1- and T2-weighted images in some fibroblastic lesions, identification of hemosiderin and a synovial origin in pigmented villonodular synovitis, or the presence of multiple target signs on T2-weighted images in deep plexiform neurofibroma. In a large number of cases, however, tissue biopsy is required for final diagnosis.

Results of total hip and total knee arthroplasties in patients with synovial chondromatosis

This retrospective analysis examines the outcome of total joint arthroplasty for severe arthritis in patients with synovial chondromatosis. All 11 patients treated with total hip arthroplasty (n = 7) or total knee arthroplasty (n = 4) returned for follow-up at a mean of 10.8 years after surgery. Pain and functional scores improved significantly in all patients. Knee range of motion improved in all patients. Synovial chondromatosis recurred in 1 knee (25%) and 1 hip (14%). Total joint arthroplasty is a valuable treatment option for these patients with predictable improvement in pain and function. Knee range of motion is likely to improve but may be less than expected for primary total knee arthroplasty. Patients remain at risk for recurrence.

Synovial chondromatosis of the foot and ankle

BACKGROUND

Synovial chondromatosis (SC) is a benign condition where the synovial lining of joints, bursae, or tendon sheaths undergoes metaplasia and ultimately forms cartilaginous loose bodies. Synovial chondromatosis of the foot and ankle is exceedingly rare, and outcomes following surgical excision are largely unknown.

MATERIALS AND METHODS

An Institutional Review Board-approved retrospective review of our institution's surgical database from 1970 to 2006 revealed 8 patients with SC of the foot and/or ankle confirmed by pathology.

RESULTS

Eight patients (4 female and 4 male) presented with pain, locking, or stiffness. Average age at presentation was 37 (range, 19 to 60) years. Average followup was 9.5 (range, 1 to 31) years. Six patients had involvement of the ankle, and two, the midfoot. Four patients underwent ankle synovectomy with loose body removal, and were pain-free at last followup. One patient underwent excision and midfoot arthrodesis for severe midfoot destruction. Three patients ultimately underwent below knee amputation, one for multiple recurrences and two for malignant transformation to low-grade chondrosarcoma.

CONCLUSION

To our knowledge, this is the largest reported series of patients with SC of the foot and ankle. In half the patients, synovectomy with excision of loose bodies resulted in pain free return to normal function, without recurrence, at last followup. However, recurrence occurred in 3 (37.5%) of 8 patients with subsequent malignant transformation to low-grade chondrosarcoma occurring in 2 patients.

Characterisation of intra-articular soft tissue tumours and tumour-like lesions

The aim of this study was to describe a new magnetic resonance imaging (MRI) classification system for intra-articular soft tissue tumours based on the morphology of the lesion, with the aim to aid the differential diagnosis. We performed a retrospective review of 52 consecutive patients presenting to a specialist musculoskeletal oncology unit with a suspected intra-articular tumour. Lesions were categorised into one of four groups according to a simple classification system based on their morphological features on MRI. Distinct groupings of pathologies emerged corresponding to each of the morphological categories. Particularly when combined with radiographic features of calcification and bone erosion, certain patterns were found to be characteristic of specific diagnoses. For example multifocal, calcified lesions were found exclusively in synovial osteochondromatosis and diffuse synovitis with hypointense T2-weighted signal intensity was typical of pigmented villonodular synovitis. Certain combinations of imaging features such as diffuse solid lesions and focal lesions with bone erosion were commonly associated with malignant lesions. We suggest that by classifying intra-articular masses according to their morphological features on MRI, particularly when combined with simple radiographic features, an additional parameter may be generated to aid the radiologist in making a diagnosis. In addition, particular combinations of features provide 'red flags' to increase the index of suspicion for malignancy.

Radiologic investigation of rheumatic diseases

This article reviews the current use of the wide variety of imaging modalities now available, presenting the imaging features of common and important causes of acute and chronic rheumatic disorders including juvenile idiopathic arthritis, spondyloarthropathies/enthesitis-related arthritis, sepsis, autoimmune diseases, vasculitis, and osteoporosis.

Synovial osteochondromatosis: the spectrum of imaging findings

Imaging plays a vital role in the diagnosis and management of synovial osteochondromatosis, a proliferative disorder of the synovium with associated loose body formation. The aim of this pictorial review is to illustrate the radiographic, computed tomographic and magnetic resonance appearances of various stages of the disease.

Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa?s) fat pad: pictorial review with an emphasis on MR imaging

A variety of intrinsic and extrinsic tumours and tumour-like conditions may affect the infrapatellar (Hoffa's) fat pad (IFP). MR imaging is the technique of choice in evaluating these conditions, but correlation with radiographs is important to identify those lesions producing mineralization. This pictorial review illustrates the spectrum of mass-like lesions that can affect the IFP, emphasizing the radiographic and MR findings that suggest a specific diagnosis.

Pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS) is a rare benign proliferative growth of the synovium of obscure aetiology with a wide spectrum of clinical presentations and imaging findings. The purpose of this review is to acquaint the reader with the spectrum of imaging features of PVNS using a variety of imaging techniques.

Malignant haemangiopericytoma of the knee joint: MR findings

The imaging findings of intra-articular haemangiopericytomas have not been described previously. We report on a 35-year-old man with a primary malignant haemangiopericytoma of the left knee joint. MRI demonstrated joint effusion and a heterogeneous mass with haemorrhagic components and multiple peripheral serpentine signal voids, suggesting the presence of vascular channels. Multiple pulmonary metastases were seen on chest CT. These imaging findings, although not pathognomonic, might be useful in suggesting the diagnosis of intra-articular haemangiopericytoma.

Synovial neoformations and tumours

An important group of soft tissue tumours and tumour-like lesions originates from the synovium of the joints, bursae and tendon sheaths. These include synovial chondromatosis, diffuse articular lipomatosis (lipoma arborescens), villonodular synovitis, synovial haemangioma, synovial chondroma and fibroma (intracapsular and peri-articular), primary chondrosarcoma originating from the synovium and synovial sarcoma. The main clinical symptoms of these tumours, such as pain, swelling, effusion and joint locking, are not specific, so the diagnosis can easily be missed in clinical practice. The most important clinical characteristics and the differential diagnostic clues for synovial tumours and tumour-like lesions are described in this chapter. In addition, the new results of genetic and histological studies are discussed, together with a summary of the available evidence-base for therapy.