Pigmented Villonodular Synovitis

What is Pigmented villonodular synovitis?

Pigmented villonodular synovitis can be defined as a medical condition, in which the joints of the hips and knees are affected. These are not the only joints that can be affected by this health problem – there are patients reporting joint problems at the level of the shoulder, ankle, knee, elbow, hand, hip or foot. This condition is not as common as you might expect. It affects people that are in their 3rd – 5th decade of their life, with a predilection towards the male population. Children can also suffer from pigmented villonodular synovitis. The average age for diagnosis is 30 years. The condition was described for the first time in 1941.What happens is that the joint lining actually suffers from an inflammatory process, which leads to excess growth in the respective joint. The bigger the inflammation, the bigger the growth. The more excess tissue grows, the higher the level of pain experienced by the patient. The joint is also surrounded by excess fluid, which add to the already-existent inflammation and causes further pain. At this point, any movement in the respective joint is highly painful.This is considered a benign proliferative disorder and, apart from the synovial lining of the joints, it can also affect the bursa and the tendon sheaths. Due to the villous or nodular changes that occur at the level of the affected joint, structural changes can occur (depending on the severity of these changes, the only solution might be the complete replacement of the said joint).

Forms of PVS

There are two main forms of pigmented villonodular synovitis:

Diffuse form

• The entire synovial lining of the joint is affected
• The bursa and the tendon sheath also suffer from structural changes
• Large joints are typically involved in this form
• This form is equally encountered in men and women

Focal form

• This is a rare form of synovitis, being characterized by a pedunculated lesion
• Also known as the localized form
• The small joints of the hands and feet are generally affected in this form
• Can also appear around the tendon sheaths (in this situation, it is presented as the giant cell tumor of the tendon sheath)
• In rare situations, it can affect the large joints of the body
• Most commonly found at the level of the knee joint
• More women than men suffer from the focal form

Symptoms

These are the most common symptoms that are encountered in patients suffering from this condition:

• Inflammation at the level of the above-mentioned joints
• The affected joint become rigid, with movements being painful in general
• Some patients only experience a diffuse discomfort instead of pain (the fact that the pain is not severe or localized is useful in distinguishing this condition from a meniscal tear or fracture)
• One of the most common joints to suffer from such problems is the one of the knee (66-80%), followed by the following joints: hip, ankle, shoulder, elbow
• Involvement of tendon sheaths of the hand and wrist is possible – most common sites of the disease include the long fingers, as well as the volar aspect of the index finger
• Moving the joint can elicit a popping sensation
• The onset of the symptoms is gradual, not sudden
• The symptoms can also be intermittent
• In general, the lesions are single and they affect one single joint at a time.

Causes

The exact cause that leads to the appearance of the pigmented villonodular synovitis is not known. It is certain, however, that there are no genetic factors involved. Moreover, there are no occupational or activity-related factors to be incriminated as risk factors for this condition.Among the proposed causes for pigmented villonodular synovitis, there are:

• Inflammation
• Response to previous trauma
• Repeated hemorrhages in the affected joint
• Lipid metabolism disorder
• Neoplasia (underlying etiology) – in rare situations, this condition can suffer from malignant transformation.

Diagnosis

These are the most common methods used for the diagnosis of this condition:

• Taking the medical history of the patient
• Clinical history of swelling
• Previous trauma to the respective joint
• Long history of pain and disability
• Physical examination
• Distension of the suprapatellar pouch
• Large effusion in the affected joint
• Diffuse palpable mass (40% of the patients)
• The ability to flex and extend the affected joint might be slightly decreased (not in all patients)
• Mild to moderate tenderness (90% of the patients) – the most common area in which tenderness is experienced is the patellofemoral one
• Imaging studies
• X-ray – analysis of the affected joint; may demonstrate the effusion at the level of the affected joint or the inflammation of the soft tissues surrounding the joint
• Bone mineralization – normal until the late stage of the disease
• Pressure erosions and cysts (joint sides)
• Secondary degenerative changes – long-term disease, includes the formation of osteophytes
• In the knee joint affectation – the suprapatellar pouch might present a characteristic expansion
• At the level of the hip – erosions at the level of the femur (head and neck), plus similar changes at the level of the acetabulum
• CT – demonstrates a hyperdense mass; this is represented by the soft tissues that surround the affected joint. May also suggest that repeated hemorrhages have occurred in the respective area.
• Useful for the identification of bone cysts and erosions
• May be performed with contrast substance, being followed by the joint aspiration
• Contrast substance is useful for the identification of nodular filling defects (typical cobblestone appearance of the synovium)
• MRI – in-depth analysis of the changes that have occurred at the level of the respective joint
• Characteristic – nodular intra-articular masses
• Hemosiderin deposits (leading to low signal intensity)
• Bony erosions
• Joint effusion
• Elevation of the joint capsule
• Hyperplastic synovium
• Nuclear imaging
• Bone scans – identification of areas with excessive vascularization and also of erosions (not commonly used)
• Positron emission tomography (PET) – can determine the extent of the joint involvement; also used for the confirmation of the diagnosis
• Angiography
• Not commonly used, can lead to a confusion in the diagnosis (non-specific findings)
• Fluid analysis (biopsy) – a special syringe is used to draw fluid from the affected joint. In the majority of the cases, the fluid drawn from the respective joint contains blood.

The differential diagnosis can be made with the following conditions: amyloid arthropathy, gout, synovial chondromatosis, synovial hemangioma or hemophilic arthropathy. All of these conditions present similar modifications on the MRI as the ones caused by the pigmented villonodular synovitis.The diagnosis of this condition is somewhat difficult, given the fact that it has an insidious onset and that the presentation of the disease is rather non-specific. The radiologic findings are subtle and, on the plus side, this condition has similar symptoms with a wide range of other conditions. Apart from the conditions that were already presented above, it is worth mentioning that both rheumatoid arthritis and osteoarthritis have similar symptoms. It is also believed that there are many other inflammatory, as well as neoplastic processes that can lead to similar changes in the synovial lining.The early diagnosis of pigmented villonodular synovitis is possible if one is familiar with the common symptoms all of these conditions present, as well as with the radiographic or general imaging features. Among the most common incorrect diagnoses that are made, there are the patellofemoral syndrome (also known as the extensor mechanism inflammatory arthritis) and the meniscal lesion. Ligament instability was also among the incorrect diagnoses.

Treatment

These are the most common methods of treatment employed for patients suffering from this condition:

• Removal of the joint lining
• Surgical resection (synovectomy)
• Traditional or arthroscopic approach
• The arthroscopic approach requires smaller incisions and thus promotes a better and a faster recovery; however, it is not suited for all patients
• Radiation therapy – recommended as treatment for intermittent pain; can be used as a treatment on its own or after the surgical resection of the synovial lining
• Complete replacement of the joint
• NSAIDs (acetaminophen, aspirin, ibuprofen) – recommended as symptomatic treatment, bringing the necessary relief from the pain and inflammation

These are the measures that you can take in order to improve the experienced symptoms:

• Resting the affected joint – if possible, keep it elevated, so as to ease the pressure
• In the situation that the knee or hip joint is affected, use crutches in order to take the weight off the respective limb
• Lying down is also a good idea, especially since it may reduce the associated inflammation.

It is important to understand that, left untreated, this condition can have a severe impact on the quality of life. The pain becomes worse with the passing of time, not to mention the patient will suffer tremendously, due to the loss of function and the eventual destruction of the affected joints.

Prognosis

Unfortunately, despite getting the right treatment, the rate of recurrence is quite high. The recurrence rate can be reduced by opting for the complete removal of the synovial joint lining.