A limp is a jerky, uneven, or laborious gait, usually caused by pain, weakness, or deformity. The development of a child’s gait is important to identify the etiology of a limp. Children begin to crawl at 9 months, independently walk at 12 to 15 months, and run at 18 months. At 1 year of age, the normal infant has a broad-based gait and moves the limbs rapidly with short steps with the arms flexed and without reciprocal arm movement. The foot makes contact with the ground all at once. By 3 years most adult kinematic patterns are developed. With subsequent changes in velocity and step length, an adult gait pattern is achieved at 7 years. The adult gait consists of a stance phase and a swing phase. The stance phase (60% of the gait cycle) begins when the heel of one foot strikes the ground and bears all the weight, advances to a foot flat position during midstance, and progresses to pushoff by the toes as weight gets transferred from the heel to the forefoot. The swing phase begins when the opposite foot pushes off the ground; the leg is swung forward with the foot clearing the ground until the heel makes contact with the ground. The most common cause for a limp is trauma; Table 109-1 lists other causes. The differential diagnosis is influenced by the duration and type of limp, age of the child, and the anatomic site affected.

A limp of recent onset (<2 weeks) is usually due to trauma, acute infection, or neoplastic causes. A longstanding limp is more likely to be due to developmental dysplasia of the hip (DDH), a neuromuscular or rheumatologic problem, overuse, slipped capital femoral epiphysis (SCFE) or Perthes disease. In contrast to rheumatologic disorders in which the limp is worse in the morning and gradually improves as the day progresses, in muscle disorders there is a gradually increasing muscle fatigue over the course of the day leading to a worsening of the limp.

A history of trauma should be explored. The diagnosis may be difficult if the injury is not witnessed or the alleged mechanism is inconsistent with the sustained injuries, as in nonaccidental trauma. In one study, one-third of children with osteomyelitis of the long bones reported a history of trauma, demonstrating that a history of trauma may confuse the diagnosis if the etiology of the limp is infectious.¹ Similarly, the presence of fever may confuse the clinician when trauma is a cause of a limp.

Fever may be present in septic arthritis, osteomyelitis, pyomyositis, soft-tissue infections, fasciitis, discitis, or psoas abscess or may be part of a viral prodrome as in transient synovitis. Other causes of fever include rheumatologic disorders and neoplastic disorders (e.g., leukemia, osteosarcoma, Ewing sarcoma, Langerhans cell histiocytosis, and osseous metastatic disease).

Determine the characteristics of pain, such as the location, type, severity, radiation, and aggravating and relieving factors. Pain may be referred from the lower back to the buttocks and lateral thigh, or it may be referred from the hip to the groin, thigh, or knee. Unrelenting, severe pain is a feature of osteomyelitis, septic arthritis, sickle cell vasoocclusive crisis, displaced bone fractures, and compartment syndrome. Intermittent pain or pain of a lesser severity is usually seen with transient synovitis, juvenile idiopathic arthritis, Legg–Calvé–Perthes disease, SCFE, and Osgood–Schlatter disease. Pain that worsens with activity is seen in overuse injury, stress fractures, and hypermobility syndromes. In patients with rheumatologic conditions or complex regional pain syndrome, pain improves after activity. Discordance between the history and the intensity of the pain experienced is observed in complex regional pain syndrome. A history of night-time pain may accompany neoplastic conditions such as leukemia, osteogenic sarcoma, Ewing sarcoma, or benign tumors such as osteoid osteoma. Muscle pain is a feature of myositis.

Conduct a review of systems to search for systemic causes for a limp. A sore throat may precede acute rheumatic fever with arthritis. Reactive joint pain and swelling may appear 1 to 2 weeks after a diarrheal illness. Back pain is present in discitis, spondylolisthesis, or vertebral osteomyelitis. Urticaria and fever may accompany the arthritis of serum sickness. Bleeding gums and ecchymosis are seen in vitamin C deficiency (scurvy) and poor growth, motor delay, bow legs, or knock knees observed in vitamin D deficiency (rickets). These conditions may cause bone pain and the gradual inability to walk. Henoch–Schönlein disease has a characteristic rash.

Vital Signs: Fever is likely to be associated with an infectious etiology but may be absent in 18% to 28%^2,3 of patients with septic arthritis.

General: Toddlers with painful foot conditions may crawl or ambulate on their knees. A child with a painful limb will be apprehensive and less active. Acute abdominal processes such as appendicitis and painful groin conditions such as testicular torsion and obstructed inguinal hernia may cause limping. Inspect the child’s limbs from the waist down, examining the skin for contusions, puncture wounds, deformity, pustules or abscesses, retained foreign bodies, and ecchymosis or bruises as seen in accidental or nonaccidental trauma, hemophilia, or bleeding disorders with hematoma or Henoch–Schönlein purpura. Ingrown toenails, calluses caused by tight-fitting shoes, retained foreign bodies, and puncture wounds may cause a painful limp.

Musculoskeletal: Compare both lower limbs and evaluate for warmth, point tenderness, soft-tissue or joint swelling, deformity, limb-length discrepancy, and differences in girth. Leg-length discrepancy is seen in developmental conditions (limb hypoplasia, developmental hip dysplasia, and club foot), hemihypertrophy syndromes, or posttraumatic physeal injury. Arthritis causes pain on movement of the joint. The position of comfort for the hip joint is abduction and external rotation. Severe pain and swelling in the setting of a crush injury may suggest compartment syndrome. In the absence of fever, trauma, and systemic symptoms, pain on palpation of the tendon and fascia insertion sites suggest conditions such as Osgood–Schlatter disease (tibial tubercle apophysitis), Sever disease (calcaneal apophysitis), or plantar fasciitis. Compare active and passive ranges of motion of the joints on the affected and nonaffected sides, starting with the sacroiliac joints, hips, and knees to the ankles and toes (Table 109-2; Figs. 109-1 to 109-5).