Hip pain differential diagnosis synovitis
The many causes of hip pain are documented in other pages on this web site. Of these many causes of hip pain, only a few are associated with synovitis or inflammation of the lining of the hip joint. The first disease is called transient synovitis of the hip. Transient synovitis is the most common cause of hip pain in children. Transient synovitis usually occurs in children between the ages of 2 to 10 years of age, especially boys, usually affecting one side of the hip. It is characterized by pain in the hip, groin and inner thigh, limping, difficulty with walking or standing, decreased range of motion of hip joint, and low-grade fever. Although the cause is unknown, it is believed that viral infections or minor injuries initiate the inflammation of the synovial membrane. Transient synovitis is important because it is similar with early stages of other conditions such as tuberculous arthritis and Legg-Calve-Perthes disease. A high fever over 99.5 degrees Fahrenheit is suggestive of other diseases. X-Rays are usually normal in transient hip synovitis. In blood tests, an ESR can be slightly elevated. X-Rays and blood tests help to rule out other diseases. If other diseases are suspected, further tests are required. Rest and anti-inflammatory medications help to relieve the pain. If these do not work, don't worry. The pain usually goes away within 2 weeks. Septic arthritis is a medical emergency. In this situation, a patient will have severe pain in the groin and will be unable to move the hip. They will usually hold the hip slightly flexed. Fever and chills will also be common. Arthrocentesis will reveal evidence of inflammation and infection. Depending on the severity of the infection this may be treated with high dose intravenous antibiotics and frequent aspiration of pus from the joint. Quite often though, surgery to drain the hip is required. The hip is the second most common location for pigmented villonodular synovitis. Like patients with knee disease, those with hip disease usually present with deep monoarticular pain of variable duration (a few months to a few years). The pain is often alleviated only by rest. Patients may localize the pain to the anterior groin or the lateral aspect of the hip. The pain is frequently intermittent, with completely asymptomatic periods in which patients are able to participate in all activities. Patients occasionally report episodes of extreme pain, which may represent hemorrhage into the joint space. During these exacerbations, patients may be able to relieve the pain by positioning their hip in a flexed and externally rotated position. This positional relief of pain is typical of a joint effusion or inflammatory process of the synovium, in that the repositioning minimizes pressure within the joint. Patients may also report decreased active and passive range of motion. A small number of patients (6.9 percent) can recall a specific traumatic event associated with the onset of symptoms, although this association may be coincidental. In pigmented villonodular synovitis of the hip, radiographs show bony erosions in thehead and neck of the femur and acetabulum in 95 percent of patients. These erosions are found early in the course of hip disease and appear as cystlike structures on anteroposterior radiographs. An average of three to four erosions, ranging from a few millimeters to 5 cm in diameter, are typically seen . A thin sclerotic rim may also be present and is due to the slow growth of the process.
Erosions are much more common in pigmented villonodular synovitis of the hip than the knee, primarily because the tight capsule of the hip joint does not allow the joint to expand to accommodate the hyperplastic synovium. As a result, intracapsular pressure increases, and bone erosion occurs. In the late stages of the disease, the articular joint space decreases, most often superolaterally, in 70 to 75 percent of patients. MRI is highly sensitive and specific for the diagnosis of pigmented villonodular synovitis of the hip. Characteristic MRI findings include hip joint effusion, lifting of the joint capsule, low signal intensity on both T1- and T2-weighted images (because of hemosiderin deposition), hyperplastic synovium (that appears as a lobulated synovial mass), bony erosions and preservation of bone density. On computed tomographic scans, the cystic erosions appear as a decreased signal of the marrow of the femoral head . Pigmented villonodular synovitis should be considered in the differential diagnosis of patients from 20 to 45 years of age who have monoarticular symptoms . Most patients with this disease have a long history of pain and disability. The presence of nontraumatic effusions of the hip or knee should further raise the index of suspicion. Plain radiographs are the first studies that should be performed. In many patients, radiographs will be normal or show only subtle findings. Patients with nontraumatic knee effusions should then undergo arthrocentesis. The finding of blood-tinged fluid is highly suggestive, although not pathognomonic, of pigmented villonodular synovitis. MRI should be performed to further suggest the diagnosis and define the extent of the disease process. In patients with hip lesions, an effusion usually cannot be identified by palpation. Thus, MRI is usually performed to search for hip effusion and hypertrophic synovium before arthrocentesis is considered or attempted. Technetium-99m etidronate bone scanning may show diffuse mild uptake when bone erosions are present. However, the study may reveal no findings when the disease is confined to the synovium. Thus, a normal bone scan does not exclude the diagnosis of pigmented villonodular synovitis. The diagnosis of pigmented villonodular synovitis is confirmed by biopsy of the synovium. The treatment of choice is synovectomy. Associated bony lesions should be carefully curettaged, and bone grafting should be performed as necessary. Diffuse pigmented villonodular synovitis has a high rate of local recurrence. The role of radiation therapy in the management of refractory disease is not clear. In one retrospective series, 13 of 14 patients with recurrent or extensive diffuse disease treated with radiation therapy were disease-free at a mean follow-up period of 69 months. Eleven patients were characterized as having good or excellent limb function, and three patients had fair function. Radiotherapy can be considered in patients with previous adequate resection of disease who experience local relapse and in patients with a large amount of disease in whom complete resection is not possible. Synovectomy may not relieve all symptoms in patients with significant destructive changes in the joint. In these situations, arthrodesis or total joint replacement should be considered. A series of 11 patients with active diffuse pigmented villonodular synovitis of the knee treated with synovectomy and total knee arthroplasty showed a local control rate of approximately 70 percent and good to excellent joint function at a mean follow-up period of 10.8 years. Rheumatoid arthritis may also affect the hip. This disease affects joints in a symmetric fashion. Small joints are affected earlier than large ones. Usually, by the time a patient has severe hip inflammation, their diagnosis will be evident and many other joints will be involved. Clinical exam will show the patient to have pain in the groin with limited range of motion because of pain. Patients will often hold the hip in slight flexion. MRI scanning may help establish the presence of synovitis. This is an indication the patient needs better control of their condition. Anti-inflammatory medications, physical therapy, and better systemic control will help. Patients often require steroid injection. As with any painful inflamed joint it is mandatory to rule out an infection so arthrocentesis of the hip should be performed prior to injecting steroids. Juvenile forms of rheumatoid arthritis, unlike the adult form, favor the hip. Pediatric rheumatology evaluation is recommended. Spondyloarthropathies (inflammatory forms of arthritis that may affect the spine) such as psoriatic arthritis and Reiters disease may also affect the hip and cause hip pain with synovitis. This group of diseases tends to affect the hip often. The key here is differentiating hip disease which usually presents with pain in the groin as opposed to sacroiliac disease or lumbar spine disease which may cause symptoms in the buttock region. Patients will mistakenly assume this pain is situated in the hip when it actually is referred pain from the spine or SI joints. The approach to diagnosis and treatment is similar to that for rheumatoid arthritis. Crystal-induced forms of arthritis such as gout and pseudogout may also affect the hip and cause synovitis and effusion (excess synovial fluid). Aspiration of fluid from the hip will help establish the diagnosis. Anti-inflammatory medication, steroid injection, anti-uric acid therapy in the case of gout will benefit as well. Osteoarthritis of the hip presents in middle-aged or older people. If it occurs in younger patients, it is due to either hip dysplasia or previously undiagnosed avascular necrosis. When severe, it will cause pain that is due to a combination of mechanical factors as well as synovitis. Groin pain and limited internal rotation will be the major clues to diagnosis. Patients will often have difficulty getting their shoes and sox on and off. The diagnosis is made clinically and confirmed by x-ray. Treatment may consist of anti-inflammatory medication as well as physical therapy and stretching exercises. End stage disease- defined as disease that causes intractable pain or marked limitation of activities of daily living- will require hip joint replacement. Loose bodies- pieces of cartilage or bone that break off and migrate around in the joint- may cause hip pain and synovitis. Symptoms include pain, particularly with weight-bearing. Diagnosis can be confirmed by MRI. Arthroscopic treatment may be helpful.
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