Continuing Education Activity

Synovial chondromatosis typically presents with large joint effusion(s), and joints may appear deformed due to swelling or synovial hypertrophy. Synovial chondromatosis can result in severe disability and dysfunction. However, most cases are benign, and this condition rarely undergoes malignant transformation. The initial diagnosis of synovial chondromatosis is made through a thorough history, physical examination, and radiological evaluation of an affected joint. Involved joints are painful at rest, and pain is worsened with motion. The range of motion is usually decreased, and x-ray evaluation reveals multiple loose radio-opaque chondroid bodies of varied sizes within the joint. This activity addresses the presentation, evaluation, and management of synovial chondromatosis and examines the role of an interprofessional team approach to the care of affected patients.

Objectives:

• Identify the presentations of the primary and secondary forms of synovial chrondromatosis.
• Describe the pathophysiology of synovial chondromatosis.
• Outline the management of the primary and secondary forms of synovial chrondromatosis.
• Summarize interprofessional team strategies for improving care coordination and communication to enhance outcomes for patients affected by synovial chondromatosis.

Introduction

Synovial chondromatosis (SC) is a benign uncommon condition of the synovial membrane of joints, tendon sheaths, and bursae that can result in severe disability and dysfunction of an involved synovial joint. Observation of involved cases indicates that this benign condition rarely undergoes malignant transformation; however, transformation to chondrosarcoma is a possible complication. [1] Ambrose Pare was the first to describe synovial chondromatosis in the knee in 1558.[2] Then, in 1813, Laennec described intra-articular loose bodies originating from subsynovial tissues.[3][4] 

The initial diagnosis is made through a thorough history, physical examination, and radiological evaluation of an affected joint. These joints usually present as having a large effusion and sometimes appear deformed due to swelling or synovial hypertrophy. They are painful at rest and are more painful with motion. The range of motion is usually decreased. X-ray evaluation reveals multiple loose radio-opaque chondroid bodies of varied sizes in a joint. MRI arthrogram enables better evaluation of the process and the extent of involvement within the joint and surrounding tissue. Synovial chondromatosis is usually monoarticular, although rare cases of multiple joint involvements occur. The process may occur in two forms: primary synovial chondromatosis (also referred to as synovial osteochondromatosis, synovial chondrosis, Reichel syndrome, or synovial chondrometaplasia) and secondary synovial chondromatosis).[5][6] The primary and secondary forms have different presentations and, as such, are treated differently. In rare cases, an extra-articular form of the condition can be identified. In these cases, the lesions are found in bursal tissue and/or in tenosynovial tissue in proximity to an involved joint.[7][8][9][10]

Etiology

The etiology of the primary form has not been determined. Elevated levels of bone morphogenic protein in the loose body lesions and the affected synovial joints of patients with primary synovial chondromatosis have been documented. However, the etiological importance of this has not been determined. Similarly, elevated levels of interleukin-6 and vascular endothelial growth factor-A have been found in these joints, but the importance of these findings is not certain. Secondary synovial chondromatosis is felt to occur as a result of mechanical changes in a joint due to arthropathy. The formation of loose chondral bodies is thought to be part of the degenerative process in these joints. The disease process, whether primary or secondary, results in the formation of multiple chondroid nodules and osteochondral or osseous loose bodies.[6][11][12][13] A monoarticular involvement is a usual presentation; however, over 33 different localizations have been described until now.[1] Intraarticular pathology is typical, but extraarticular cases have also been reported where it typically involves tenosynovial structures.[14][15]

Epidemiology

Men are reported to be affected with synovial chondromatosis up to four times more commonly than women. The knee is the most common joint affected. Typically affects diarthrodial, weight-bearing joints of individuals 30-60 years of age. The following joints are affected in descending order of frequency: knee (70%), hip (20%), shoulder, elbow, ankle, and wrist.[3][12][14][16][6][17][18] As a general observation, the larger the joint and the more weight it bears, the greater potential for synovial chondromatosis development. It has also been reported to affect the temporomandibular joint, the intervertebral facet joints, and a variety of tenosynovial locations.[15][19][20] 

A rare occurrence is an extra-articular presentation of synovial-chondral lesions. This occurs in synovial lined bursal tissue or tenosynovium, where the typical chondral loose bodies form. These are referred to as tenosynovial chondromatosis or bursal chondromatosis. Synovial chondromatosis occurs most commonly in the fifth decade of life; it is rarely present before age 20 and is very rare in children. Reference to both the primary form (no evidence of concurrent joint pathology) and secondary form (occurring in the setting of joint degeneration) is made in the literature. The secondary form occurs more commonly and usually in older individuals. However, both primary and secondary forms are uncommon arthropathy.[6][12][16][20] Despite the fact that the exact incidence is unknown, it has been reported as 1.8 per million individuals per year in England.[3] With a 10% incidence of being bilateral.

Pathophysiology

Synovial chondromatosis develops as cartilaginous foci in synovial membranes, bursae, and tendon sheaths. [12][13][16] It typically develops as metaplasia with the lack of atypia and invasion; however, it is also considered neoplastic due to its association with clonal chromosomal changes, especially recurrent chromosome 6 abnormalities which have been noted in 5 (62%) out of 8 cases.[21][22][23] The cartilaginous foci originate as sessile with good synovial attachment. As they grow, they become more pedunculated, then they break loose and become free intraarticular or periarticular loose bodies.[13][20] Once they are loose in the joint, they continue to grow based on nutrition from the synovial fluid and end up with either reattachment to the synovium or reabsorbed. Grossly and microscopically, the major proportion of these loose bodies is in a transitional zone between synovium and hyaline cartilage due to the abundance of pluripotent stem cells in this area.[12][24] 

The hyaline cartilage is hypercellular, and the cells are often atypical. These atypical changes are multinucleated cells, myxoid degeneration of matrix, crowding of cell nuclei, and large nuclei. Almost two-thirds of these loose bodies will ossify through endochondral ossification, while the rest will be unossified.[25] The number of loose bodies varies anywhere from two or three loose bodies to several dozens. They present in varied sizes, and several loose bodies may combine to form larger bodies. The number of intraarticular lesions is greater in the primary type than in the secondary type. High levels of bone morphogenic protein have been found in the loose cartilaginous bodies and synovial tissue. Usually, in primary synovial chondromatosis, loose bodies are small, rounded, and uniform in size. Whereas in secondary synovial chondromatosis, loose bodies are more variable. The loose bodies may create pathological mechanical wear on joint surfaces and result in various types of erosion of articular surfaces. The process is classified as a benign neoplastic rather than a metaplastic lesion.

Primary or idiopathic synovial chondromatosis involves otherwise normal joints with no association with trauma, infection, synovial irritation, or genetics. It presents at an earlier age, 30 to 40, and is relatively rare. This is compared to secondary synovial chondromatosis, where there is an underlying joint pathology resulting in synovitis and/or articular destruction such as trauma (single traumatic event or repetitive microtrauma), osteochondritis dissecans, advanced osteonecrosis, or Charcot neuropathic joint. Patients with secondary synovial chondromatosis are relatively older, in their 50s to 60s.

There is no consensus on whether synovial chondromatosis is neoplastic or metaplastic. However, there is a small risk of malignant transformation to chondrosarcoma. Despite the rarity of malignant transformation, it is associated with recurrence after initial treatment.[17][26] Whereas it is uncommon for untreated cases to transform into chondrosarcoma. The malignant transformation rate is unknown; however, in a large orthopedic oncology database, out of seventy-eight patients with primary synovial chondromatosis, five developed malignant chondrosarcomas.[3]

History and Physical

The presentation of SC is relatively nonspecific. Patients can be asymptomatic, and when symptomatic, patients typically will present with joint pain as a chief complaint. In association with swelling, reduced range of motion, and occasionally crepitus and mechanical locking.[3][6][12][27][28] 

Symptoms are usually worse with activity but can also present at rest. Patients may less commonly report instability, joint effusions, or evidence of involvement of the surrounding neurovascular structures.[20] It is most frequently monoarticular in the primary form and may be multi-articular in the secondary form. Primary chondromatosis can rarely recur. In the secondary form, a history of osteoarthritis, post-traumatic arthritis, or rheumatoid arthritis may be present. Diagnosis is usually an incidental finding and is often delayed. A reported average time from onset of symptoms to diagnosis is five years.[3]

Evaluation

Radiographic findings enable the differentiation of primary from secondary types. The primary type can be diagnosed if radiographs indicate no underlying joint pathology. MRI and MRI arthrography are also helpful in making the diagnosis. MRI can help differentiate and diagnose the bursal extension of the disease process. In the hip bursal extension into the iliopsoas and obturator externus, the bursa has been identified in up to 71% of the cases. An evaluation of patients with findings that suggest secondary synovial chondromatosis should include an attempt to identify underlying arthritic processes.[29][30][31][32][33]

Radiographs will show multifocal, rounded, articular, or periarticular calcific densities (pathognomonic of synovial chondromatosis).[20] However, care should be taken to exclude the diagnosis based on the radiographs only, as in 20% of cases, calcification and mineralization will be delayed as they are time-dependent. nonminerazlied nodules can vaguely fill the joint or bursa, even resembling an effusion. Moreover, clinically, patients may be symptomatic months to years before the development of calcifications.

 Serial radiographs are indicated after treatment to monitor the recurrence or development of degenerative changes.[6][25]

Cross-sectional imaging  (computed tomography (CT) and magnetic resonance imaging (MRI): This can be helpful in the early pre-mineralization stage of the disease.[12][13][6] In addition to its usefulness in early diagnosis, it evaluates the joint articular surfaces and adjacent structures and the extent of the disease.

MRI: T1- weighted images will show loose bodies with low signal intensity but higher than the muscular tissue. Whereas, in T2- weighted images, loose bodies will display a high signal intensity typical of the high water content of cartilage.

CT: Better visualization of the mineralized areas, which are hypointense in all MRI sequences.  

Treatment / Management

Synovial chondromatosis can be a self-limiting disease. So, conservative management can work for some patients. Nonsteroidal anti-inflammatory drugs (NSAIDs), modification of activities, and cryotherapy might be considered.[14] However, reduced range of motion and mechanical symptoms of locking and catching from loose bodies can have deleterious consequences with joint destruction. Hence, the definitive management of synovial chondromatosis is the surgical removal of loose bodies with or without synovectomy.  

Surgical Management

The Necessity of Synovectomy is Controversial

Synovectomy for a synovium-based pathology sounds to be the primary indicated management. However, there is no strong evidence in favor of this option, along with surgical removal of the loose bodies.[20][34] In the past, multiple studies supported the option of performing isolated removal of loose bodies with no additional synovectomy, as there is no superiority for such an addition.[35][36][37][38]

In other studies, synovectomy was supported as a means of preventing recurrence.[39][40][41]

Additionally, whether to perform the synovectomy arthroscopically or through an open approach is controversial. Open synovectomy offers better visualization of the joint surfaces. Whereas arthroscopic management has lower morbidity, quicker return to function, short hospital stay, reduced postoperative pain, and quicker rehabilitation.[41][42]

Secondary synovial chondromatosis is managed by anti-inflammatory medication with the additional management of the inflammatory joint symptoms until or unless mechanical symptoms prohibit adequate function. At this point, surgical management is indicated. Surgical management should address improving long-term function and prognoses. As such, joint reconstruction or arthroplasty, in addition to removing loose bodies, is indicated.

Differential Diagnosis

Some pathologies result in the formation of intra-articular loose bodies or synovial proliferation.[6][12][14][16] These include:

• Crystal deposition disease (tendinosis Calcarea)
• Osteocartilaginous loose bodies
• Osteochondritis dissecans
• Neurotrophic arthritis
• Rheumatoid arthritis
• Degenerative arthritis
• Tuberculous arthritis
• Osteochondral fractures
• Soft tissue tumors

Other benign synovial disorders include synovial hemangioma, lipoma arborescent, and pigmented villonodular synovitis (PVNS).

Differential diagnosis should also consider the possibility of a malignant lesion. Interosseous low-grade chondrosarcoma that extends into a joint and synovial cell sarcoma can be considered if the lesions involve bone adjacent to a joint. MRI findings help differentiate possible malignant. Marrow invasion is not usual with synovial chondromatosis. It is more likely to be present with malignant lesions.

For both the clinician and the pathologist, it can be challenging to distinguish synovial chondromatosis from chondrosarcoma. The classic indicators of malignancy, such as bony invasion, permeation, and destructive growth across joints, develop late in the disease course. Recurrence (especially multiple episodes of recurrence) is a significant sign that warrants consideration of malignant transformation. However, the number of lesions, the size, or the rate of change do not correlate with malignancy.[43]

Staging

In 1977, Milgram was reported to be a self-limiting disease. Macroscopically and microscopically, it was classified into three stages:[44]

Stage I: An active, inflammatory intrasynovial process without loose bodies. It could be asymptomatic or present with localized joint pain and swelling. 

Stage II:  Active synovial proliferation with transitional loose bodies (between synovium and hyaline cartilage from pedunculated to free loose bodies). Patients present with mechanical symptoms and decreased range of motion.

Stage III: A quiescent stage of the disease with no ongoing metaplasia. Several loose bodies with minimal synovial disease and inflammation. Patients tend to be asymptomatic in this stage as well. 

Prognosis

Intraarticular or periarticular destruction can be a sequel of synovial chondromatosis. Hence, prompt diagnosis and treatment will assist in avoiding secondary pathology.[6] The most important prognostic factor is the status of the articular cartilage coverage of the involved joint.[37]

Recurrence: There is rarely a reoccurrence of primary synovial chondromatosis after surgical management with the removal of the loose bodies and partial synovectomy. Reoccurrence has been reported in a case involving the temporal mandibular joint.

Regression: Despite uncommon, spontaneous regression has been reported in the literature. But, it often takes several years from the onset to the resolution of symptoms.[11][13][28][45] 

Postoperative and Rehabilitation Care

Post-operative management includes a progressive range of motion and strengthening of peri-articular muscle groups. The use of post-operative non-steroidal anti-inflammatory medication is not confirmed as being beneficial. 

Enhancing Healthcare Team Outcomes

When patients present to the primary care provider or nurse practitioner with joint pain, the differential diagnosis is vast. Synovial chondromatosis is one condition that can present with joint pain and is best managed by an orthopedic surgeon. The management of primary synovial chondromatosis is through surgery. Current arthroscopic surgical techniques allow for arthroscopic surgical management; however, occasionally, open procedures may be necessary. 

Post-operative management includes a progressive range of motion and strengthening of peri-articular muscle groups. Secondary synovial chondromatosis is initially managed by anti-inflammatory medication unless mechanical symptoms prohibit adequate function. At this point, surgical management is indicated. Surgical management should address improving long-term function and prognoses. As such, joint reconstruction or arthroplasty, in addition to removing loose bodies, is indicated.[46][47][48]

An interprofessional healthcare team consisting of clinicians (MDs, DOs, NPs, and PAs), orthopedic specialists, nurses, and physical therapists, engaging in open communication to ensure all team members have the information they need to advance the patient's outcome, will generate the best outcomes. [Level 5]