The Limping Child
John M. (Jack) Flynn, MD
David L. Skaggs, MD, MMM
Michael G. Vitale, MD, MPH
Haemish Crawford, FRACS1
Nicholas D. Fletcher, MD1
THE GURU SAYS…
The history is as important as the observations. The differential diagnosis of a limping child is so vast and can range from a benign mild leg length discrepancy through to leukemia. One must ask about systemic symptoms of fatigue, fever, and weight loss.
While many children presenting with a limp will have benign, self-limiting causes, the pediatric orthopaedic surgeon must keep their guard up to stay out of trouble and not miss something more serious. This is one of the most common reasons children are brought to our office, and the list of possible causes is long. Always take the parents’ concern seriously. If a patient’s mother says there is a limp, you should find it or prove her wrong. This is one of the areas where spending some time taking a good history is critical. Nail down the details regarding how long the limp has been there and the circumstances surrounding its first recognition.
Essential Questions When Evaluating a Limp1
Reprinted with permission from Flynn JM, Widmann RF. The limping child: evaluation and diagnosis. J Am Acad Orthop Surg. 2001;9(2):89-98. Copyright © 2001 by American Academy of Orthopaedic Surgeons.
Get the child out into the hallway, and get him or her in shorts so you can see the whole lower limb. Do not hesitate to have the child walk or even run down the hallway. It’s helpful to look at each segment (e.g., foot, ankle, knee, hip, torso) separately with each pass. Be patient as more subtle limps can become more obvious as the child becomes tired or forgets the doctor is watching.
During the tabletop exam, look at the whole limb (including the bottom of the feet). Look for subtle signs of muscle atrophy, swelling, or discoloration. When faced with the typically frustrating scenario of a limping toddler with normal x-rays and no helpful details in the history, search for the point of maximum tenderness (PMT). The PMT can sometimes be a little confusing. Thigh or knee pain (rubbing) is a clue to think of hip pathology. Remember, a toddler’s fracture does not have to be in the tibia; it can be in the calcaneus or elsewhere (Fig. 13-1). Unless an obvious source reveals itself quickly (i.e., toddler fracture), range every joint (and that includes spine flexion/extension) (Fig. 13-2).
THE GURU SAYS…
Remember that spinal disorders, especially diskitis, are a common cause of a limp in the young child. Having the patient pick up a cell phone or toy placed on the floor can elicit the source of pain.
One way to think of the causes of limping is to consider the differential anatomically, from bottom to top: the ones on the top are often more serious (spinal cord tumor), more easily overlooked (diskitis), and are more difficult to localize on a physical exam since the structures are not as superficial (iliacus abscess).
To recognize an abnormality, the orthopaedist needs to understand what normal should be for a given age. New walkers have a wide base gait, poor balance, and a tendency to toe walk, but none of these are “limps” (except maybe in the worried mind of a new parent). There are five unique limps, or abnormal gaits in children: antalgic, Trendelenburg, spastic, muscle weakness, and short limb gait. An antalgic limp does not have to come from the leg. It can come from the spine, pelvis, or sacroiliac joint. Sometimes you need to watch a longer stretch of walking or get the child to run in order to appreciate a subtler Trendelenburg gait. In a spastic gait, spasticity will affect the whole limb, so watch for the effects on multiple joints one at a time—floor to spine.
THE GURU SAYS…
While observing the gait, ask the child to walk on their toes and then heels. Ask them to sit on the floor and stand up. This gives you a quick assessment of neurologic status and muscle power.
Look for signs of contracture (equinus, crouch gait due to hamstring contracture), or decreased motion and its effects (decreased knee motion is due to rectus spasticity, causing toe dragging). If suspicious of spasticity, always get the child to run. You may pick up subtle upper extremity posturing that clinches the diagnosis. A muscle weakness gait is seen in conditions such as Duchenne muscular dystrophy (DMD). To the uninitiated, this may not look like a “limp,” just a “funny walk.” It will be hard for the parent to describe, and it will come on gradually. You might see a lurch. Do a Gower test if there is any suspicion. Any loss of milestones is extremely concerning.
THE GURU SAYS…
Muscular dystrophy is often forgotten as a presenting cause of limp in modern medicine given the easier path to a genetically proven diagnosis, but this may continue to be one of the few conditions that you may be the first to diagnose. Always remember the Gower test in any boy with a new onset of a change in gait.
Imaging, Blood Work, and Other Diagnostic Tests
The presence or absence of pain, age, site of symptoms, and type of limp will help establish the differential diagnosis (Table 13-1). Make the pace and intensity of your workup (lots of tests immediately vs. watch and revisit) appropriate for the conditions on your differential diagnosis. Sometimes doing too much testing causes as much trouble as doing too little (e.g., you find some unrelated red herring on MRI that someone wants to biopsy and there is really nothing there. Or, you put a toddler under general anesthesia for an MRI that’s not really needed). Good plain radiographs are always the starting point; they are quick, widely available, sensitive, and specific for many things on the differential diagnosis (Fig. 13-3). Oblique radiographs (especially of the foot) are valuable for seeing subtle abnormalities that might cause a limp. To stay out of trouble, keep in mind that plain radiographs may reveal no sign of early osteomyelitis. It can take 10 or more days for signs of infection to produce radiographic changes of the bone. Instead, the best early radiographic finding may be soft-tissue swelling. Comparison views may be helpful in seeing such subtle signs.