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Synovial chondromatosis - Foot and Ankle

Summary

(See source below) Synovial chondromatosis is a rare benign condition characterized by the presence of cartilaginous nodules in the synovium of joints, tendon sheaths, and bursae which often occur without trauma or inflammation [1,9,10]. Synovial chondromatosis originates from cartilaginous metaplasia of synovial tissue near joints, tendon sheaths, or bursae.

Synovial chondromatosis is usually identified in the third to fifth decades of life and is rarely seen in children [6,7].
The onset is described as insidious and occurs over months to years [2]. Patients may report pain and swelling within a joint.
The lesion is lobular, well-defined, and has low signal intensity on T1 weighted images and high signal intensity on T2 weighted images.
Treatment consists of arthroscopic or open surgical removal.
Complete Information on this Tumor
Introduction and Definition: 

(see source below) Synovial chondromatosis is a rare benign condition characterized by the presence of cartilaginous nodules in the synovium of joints, tendon sheaths, and bursae which often occur without trauma or inflammation [1,9,10]. Synovial chondromatosis originates from cartilaginous metaplasia of synovial tissue near joints, tendon sheaths, or bursae. This condition is occasionally seen around the ankle but is rare in the foot. The lesions can achieve a significant size and presented diagnostic dilemma. With disease progression, the loose bodies may ossify and can be identified radiographically [11]. There are a variety of names for this lesion. The most commonly accepted include synovial chondromatosis, synoviochondrometaplasia, synovial chondrosis, synovial osteochondromatosis, and articular chondrosis [2,11].

The condition is generally thought to be monoarticular and over 50% of reported cases occur in the knee [6,12]. Other locations include the hip, elbow, shoulder, and ankle joints, although any synovial joints can be affected [7,13,14].

It is generally agreed that the exact aetiology of synovial chondromatosis is unknown and controversy exists surrounding proposed hypotheses. Milgram, in 1977, categorized the disease process into 3 distinct phases [15]. In phase I, metaplasia of the synovial intima occurs. Active synovitis and nodule formation is present, but no calcifications can be identified. In phase II, nodular synovitis and loose bodies are present in the joint. The loose bodies are primarily still cartilaginous. In phase III, the loose bodies remain but the synovitis has resolved. The loose bodies also have a tendency to unite and calcify [15]. Because there is no evidence of histologic metaplasia in stage three, diagnosis may be more difficult.

Despite the varied nomenclature, it is recognized that synovial chondromatosis can be differentiated into a primary and secondary form. The primary form occurs in an otherwise normal joint [4]. Primary synovial chondromatosis is characterized by undifferentiated stem cell proliferation in the stratum synoviale [16]. The pathological process is considered to be a cartilaginous metaplasia of synovial cells with trauma commonly thought of as an inciting stimulus, although no statistical relationship has been reported in the literature. Via immunostaining, it has been concluded that primary synovial chondromatosis is a metaplastic condition [17]. The individual nodules may detach from the synovium and form loose bodies in the joint. These loose bodies may continue to grow, being nourished by the synovial fluid. These nodules can continue on to calcify, known as osteochondromatosis, although it is reported that calcification is only present in 2/3 of patients. Some have hypothesized that this form is actually a secondary disorder following cartilage shedding into a joint [18]. Primary synovial chondromatosis is generally thought to be progressive, more likely to recur, and may lead to severe degenerative arthritis with long-term presence [11,12].

Secondary synovial chondromatosis is thought to be caused by irritation of the synovial tissue of the affected joint [4,14]. It occurs when cartilage fragments detach from articular surfaces and become embedded in the synovium. These loose bodies are nourished by the synovium, induce a metaplastic change in the subsynovium, and consequently produce chondroid nodules [14]. This form is associated with degenerative joint disease, trauma, inflammatory and non-inflammatory arthropathies, avascular necrosis, and osteochondritis dissecans [14]. This form is not likely to recur following surgical removal [11].

Incidence and Demographics: 
Synovial chondromatosis is usually identified in the third to fifth decades of life and is rarely seen in children [6,7]. It is more commonly identified in males, with almost a two-to-one ratio in comparison with women [2,11].
Symptoms and Presentation: 

The onset is described as insidious and occurs over months to years [2]. Iossifidis et al described an insidious, non-specific clinical presentation in their case of ankle synovial chondromatosis [6]. The diagnosis of synovial chondromatosis is often made following a thorough history, physical examination, and radiographic examination. Patients may report pain and swelling within a joint. This is routinely exacerbated with physical activity. Commonly, the patient may also report aching, reduced range of motion, palpable nodules, locking, or clicking of the joint [7,11]. These lesions may become symptomatic following mechanical compression or irritation of soft tissues, nerves, or malignant transformation. In rare cases, reactive bursas can form over osteochondromas. These may be another source of pain, but can also mimic chondrosarcoma [14]. Conversely, individuals may have no signs or symptoms and it is an incidental finding secondary to another complaint. According to Milgram, this is related to the stage of the lesion [15].

X-Ray Appearance and Advanced Imaging Findings: 
The lesion characteristically is adjacent to a joint or contained within the tendon sheath, and has MRI features characteristic of a partially calcified cartilage. The lesion is lobular, well-defined, and has low signal intensity on T1 weighted images and high signal intensity on T2 weighted images. According to Milgram's classification, plain film radiographs are only helpful in the third phase of the disease, once calcification has occurred [15]. Advanced imaging, such as CT and MRI scans are useful in identifying and localizing the lesions as well as helping to distinguish between other differential diagnoses. When imaging does not provide specific diagnostic features, it is important to obtain a tissue biopsy. A definitive diagnosis is made histologically via a synovial tissue biopsy. Blood tests and arthritis profiles can also help rule out specific differential diagnoses.
Differential Diagnosis: 
Potential differential diagnoses include osteochondritis dissecans, synovial vascular malformation, pigmented villonodular synovitis, chondrosarcoma, injury-related soft-tissue calcification, and lipoma arborescence with osseous metaplasia [4,20].
Preferred Biopsy Technique for this Tumor: 
If the diagnosis is not definitive, it is recommended to biopsy and debride initially.
Treatment Options for this Tumor: 
Treatment consists of arthroscopic or open surgical removal. Since the condition tends to be progressive but self-limiting, indications for surgery depend on the level of symptomatic presentation in addition to the functional demands of the patient [6]. In asymptomatic patients, the nodules may resorb over time and invasive procedures should be avoided [4]. Patient age and disease stage may also serve as treatment guides. In young patients, arthroscopic debridement is commonly sufficient to achieve a cure and synovectomies should be used only in instances of relapse [10]. In phase III disease, removal of the loose bodies alone is sufficient [13]. Resection of the loose bodies and synovectomy when synovitis is present is thought to be indicated since the recurrence is increased when synovitis is present [13].
Outcomes of Treatment and Prognosis: 
Recent interest in this diagnosis has occurred due to the potential for malignant degeneration. Although rare, there are a number of reported cases and patients diagnosed with this condition should be monitored [3]. In a 1998 study examining primary synovial chondromatosis, a relative risk of 5% for malignant degeneration was reported [19]. The progression of synovial chondromatosis to chondrosarcoma is very rare and some may argue it is simply a case of misdiagnosis. Nonetheless, a distinction between these two entities may be difficult. Clinical and radiographic features of these conditions are similar. As such, clinical, radiographic or advanced imaging, and histological evidence should be considered collectively to arrive at an accurate diagnosis. Recurrence rates for synovial chondromatosis after surgical treatment have been reported as varying from 7% to 23% [2]. Overall, prognosis following removal of the nodules is reported as excellent. Although no comparative studies for the ankle have been performed, removal of loose bodies and synovectomy of the knee produced good results in function, pain, and control of synovitis in 90% of subjects [21]. Surgery predisposes patients to tissue scarring, subsequently compromising joint function. If disabling symptoms are persistent, arthrodesis is a reasonable approach [1,6]
Suggested Reading and Reference: 
This section of the BTO site comprises material taken directly from: H Shearer, P Stern, A Brubacher, T Pringle A case report of bilateral synovial chondromatosis of the ankle Chiropractic & Osteopathy 2007, 15:18 Please see the following article: Chiropractic & Osteopathy 2007, 15:18 Heather Shearer, Paula Stern, Andrew Brubacher and Tania Pringle Department of Graduate Education and Research, Canadian Memorial Chiropractic College, Toronto, Canada