Pediatric rheumatologists often care for patients with complaints of hip pain. Hip pain may be difficult to treat and is an area which highlights the importance of collaboration between pediatric orthopedists and rheumatologists.
When hip pain presents in young children, the first priority lies in excluding infection which, if untreated, may damage the hip joint permanently.
Toxic synovitis, or transient synovitis, is an inflammatory condition of the hip seen in young children following a viral infection that is treated with rest and nonsteroidal anti-inflammatories. Many times these patients are evaluated initially by an orthopedic surgeon and may undergo a hip joint aspiration to exclude infection. These children respond quickly to medication. Toxic synovitis should not recur; therefore “recurrent” toxic synovitis should raise the suspicion for an underlying arthritic condition such as juvenile spondyloarthropathy.
Work-up for recurrent hip pain must be pursued vigilantly, as Legg-Calvé Perthes disease, tumor, occult trauma, slipped capital femoral epiphysis, congenital hip dislocation, and arthritic conditions may present with recurrent hip pain.
The hip joint is involved extremely rarely in children with pauci-articular (few joints affected, fewer than five joints at the six month mark) juvenile rheumatoid arthritis (also known as juvenile idiopathic arthritis). However, in children with juvenile spondyloarthropathies, the hip joint is involved commonly and hip pain may be the presenting complaint.
Spondyloarthropathies commonly present with morning pain or stiffness in the hips, heels, or lower back, and are most common in children over the age of 10 years. Although earlier presentations of spondyloarthropathy can be seen, younger children should be evaluated thoroughly with appropriate lab work and imaging studies. While patients with spondyloarthropathy may be HLA-B27 positive, many will be negative, and HLA-B27 negativity does not exclude this diagnosis.
The juvenile spondyloarthropathies are a group of diseases in which inflammation is present not only in the peripheral joints, but also in the insertion points of tendons into bone. Patients will complain of pain in the heels, feet, hips, and lower back. They may report a history of recurrent injuries or tendonitis and are often treated with repeated immobilization which may actually worsen their symptoms. These patients may develop peripheral as well as axial arthritis.
There are typically two groups – teenagers (more often boys) with lower back pain and arthritis of the knees, and younger patients (more often girls) with what initially may resemble pauci-articular arthritis, but which involve the small joints such as the fingers or toes (a pattern of arthritis called “dactylitis”). In dactylitis, the tendons around the toes or fingers become swollen, giving the appearance of a sausage, or so-called “sausage digit”.
Teenage boys with juvenile spondyloarthropathies are the most severely affected group. Those boys who are HLA-B27 positive with an elevated sedimentation rate are at the highest risk of progressive disease and may ultimately evolve to fulfill criteria for ankylosing spondylitis (AS). Some children affected by spondyloarthropathy are also at risk for progression to AS.
Not every child with a juvenile spondyloarthropathy has an identifiable underlying disease association, but many do. The spondyloarthropathies include psoriatic arthritis, arthritis associated with inflammatory bowel disease (or celiac disease), reactive arthritis, and Reiter’s syndrome. The nonspecific spondyloarthropathies are not associated with an underlying condition, though these may evolve over time, presenting even years after the onset of the arthritis.
Many children do well with management of their symptoms, including with non-steroidal anti-inflammatories, physical therapy, and the use of heel cups or custom-fitted orthotics.
For children with laboratory abnormalities and persistent joint pain, there is concern for low-grade joint damage over time. These patients may require more aggressive medical treatment. We are fortunate to practice in an era when many excellent medical therapies are available.
All spondyloarthropathy patients should be screened and followed by an ophthalmologist at diagnosis. Extra-articular complications of the spondyloarthopathies may include acute anterior uveitis.
Cardiac involvement, including aortitis with resulting aortic insufficiency, though rare in children, can also be seen.