You suspect that a patient you see has a limp that may indicate a more serious condition. What is the best strategy to evaluate this child? How do you know when to treat and when to refer the patient to a specialist? And finally, which tests are most useful and which others are likely to add little to the clinical assessment, except additional cost?
The etiology of a child's limp can range from simple and benign to a serious condition. When such a patient presents, focus on the child's history and physical examination. A good history, for example, can help to narrow down the long list of differential diagnoses and potential etiologies.
It is important to take parents' concerns seriously. There are essential questions to ask parents and patients. For example, is there pain? Is the child sick? Who noticed the limp first? Was the onset gradual or sudden? How long has the child had a limp? Is the limp getting better or worse, or is it staying the same?
When performing the physical examination, have the child walk a long distance, not just within the confines of the exam room. Watch the child walk and/or run from different viewpoints, including the front, back, and side. Also, have the child undress so lower extremities are exposed.
During the examination, try to determine the type of limp. Common forms include antalgic (painful), Trendelenburg (associated with weakness), and limps associated with a short limb, spasticity and/or stiffness, or poor balance. Another tip is to observe the child after you ask him or her to pick up an object off the floor. If the child keeps the spine stiff, it may indicate a spinal etiology for the limp.
Try to find the point of maximal tenderness during a tabletop examination. Flex each joint through its full range. During this part of the exam, also look for any atrophy, rashes, swelling, or discoloration. Consider whether the problem can be localized. Also, remember that knee pain is hip pain until proven otherwise! Keep in mind that slipped capital femoral epiphysis can present as knee pain, so check hip internal rotation. Do not forget to do the Gowers' test in boys (have the child stand from a sitting position on the floor) because if there is muscle weakness, it may be associated with Duchenne's muscular dystrophy, which occurs primarily in boys.
Limps generally can be divided into three age categories to help narrow the list of possible etiologies. For example, fractures and infection are common causes in children less than 4 years old. Infection becomes less common, and acute and/or overuse injuries and hip disorders (for example, Perthes disease, transient synovitis) become more common, in children between 4 years and 10 years old. Overuse and acute injuries are especially common among children older than 10 years.
Some tests are more useful than others in the child with a limp. For example, plain radiographs of the affected limb—including one joint above and below—can be useful. Ultrasound of the hip also can help if there is concern about the possibility of a septic hip; this imaging helps to detect the presence of an effusion. In a child with an acute, nontraumatic limp, laboratory assays including complete blood count with differential, erythrocyte sedimentation rate, and C-reaction protein test are recommended prior to referral.
In contrast, MRIs and bone scans should be ordered by the specialist who is going to treat the child based on the findings.
If the diagnosis is unclear after the initial examination, reevaluate the child on a weekly basis until the problem resolves or the diagnosis is established.
In general, pediatricians can observe a child whose limp is improving. Also, observe a limping child who can still play and perform all activities of daily living without interference. In addition, bilateral symptoms suggest a benign condition. Remember, idiopathic toe walking should be bilateral. Reassure parents that growing pains will not make a child limp.
Refer the child to a specialist when the limp does not improve over time. In addition, consider referral if the patient has constitutional symptoms associated with a new-onset, nontraumatic limp.
A child with a painful limp generally will need further evaluation unless there is an obvious cause. Remember that a limp associated with constant pain, even while the child is at rest and/or at nighttime, is worrisome, and a specialist may be able to help with diagnosis and management. And always be concerned about the child who loses the ability to walk. Also, don't forget to consider child abuse in the infant or toddler with multiple injuries.