- A delay in diagnosis may be devastating in certain cases that cause a limp such as septic joint, bone tumors, and leukemia, as well as in the case of child abuse.
- Rule out bone tumors and leukemia as possible causes of a limp.
- Consider hip pathology in children presenting with knee or thigh pain.
- A septic hip causes increased intra-articular pressure and will compromise the blood supply to the femoral head, possibly resulting in avascular necrosis unless surgical decompression is performed emergently.
A limp is a common reason for a child to visit the emergency department and it has several serious causes.1 The most common form of limp is an antalgic gait caused by pain. Gait reflects the coordinated action of the lower extremities. The body moves forward smoothly with economy of motion and energy. The stance phase (60% of the entire gait cycle) is the weight-bearing portion.2 It is initiated by heel contact and ends with toe lift-off from the same foot. Swing phase is initiated with toe off and ends with heel strike. Limb advancement occurs during the swing phase (40% of normal gait cycle). During this phase, the foot pronates first and then supinates. Pronation shortens the foot, which helps it to clear the ground. Pronation also minimizes the energy expenditure necessary for ground clearance as the non-weight-bearing limb passes the weight-bearing limb.2 Supination stabilizes the bony architecture of the foot thus preparing it for heel strike, when the foot must absorb the shock of striking the ground. In an antalgic gait, the gait is uneven because to minimize weight bearing on an injured limb, the time in stance phase is shortened in the painful limb with a resultant increase in swing phase.
The incidence of limp has been found to be 1.8 per thousand. The male-to-female ratio is 1.7:1 and the median age 4.35 years. Limp is mainly right-sided (54%) and painful (80%); 33.7% of the children have localized pain in the hip. A preceding illness has been found in 40%.3
An acute limp implies an underlying pathology that causes disruption of the standard gait pattern. The clinician must consider the spine, pelvis, and lower extremities for a possible etiology. A useful approach is to consider the causes of limping from head to foot to avoid overlooking common underlying conditions such as diskitis, psoas abscess, or septic hip, which are less obvious than conditions involving the lower extremities. In considering the differential diagnosis of an acutely limping child, the clinician should first consider broader categories of etiologies, such as traumatic, infectious, neoplastic, inflammatory, congenital, neuromuscular, or developmental causes (Table 14–1). You can further narrow the diagnosis by taking into account the age of the patient because certain diseases are more common in a given age group (Table 14–2).
Table 14-1. Differential Diagnosis of an Acutely Limping Child