A 20-month-old boy with a limp

A 20-month-old boy presented to the emergency department with a 3-day history of right-sided toe-walking and limp. There was no history of fever or trauma, and review of systems was unremarkable. He was a healthy immunized toddler with age-appropriate development. He was well-appearing and afebrile. Musculoskeletal examination demonstrated a right foot maintained in plantarflexion. The posterior calcaneus was tender to palpation with mild erythema and warmth over the heel. Passive range of motion was full but elicited pain. Knee and hip examination was unremarkable. Initial investigations revealed a white blood cell count of 15.1 × 109/L, platelets of 323 × 109/L, and C-reactive protein concentration of 2.8 mg/L. Radiographs of the right foot, tibia and fibula were normal. He was discharged home with conservative management and reassessed five days later in clinic. He remained afebrile and nonweight-bearing on the right foot with a C-reactive protein concentration of 16.4 mg/L. He was admitted to rule out osteomyelitis. Magnetic resonance imaging (MRI) of the right foot revealed no osseous infection with mild subcutaneous swelling (Figure 1). Subsequent ultrasound showed a small fluid collection deep to the right Achilles tendon with surrounding hyperemia consistent with an inflamed bursa deep to the tendon. Lateral T2-weighted magnetic resonance imaging of the right foot. Mild-to-moderate edema and enhancement of the subcutaneous tissues overlying the dorsal and plantar aspects of the calcaneal tuberosity. A toddler with limp is not uncommon but in this case common etiologies did not explain his presentation. The differential diagnosis of an acute limp and refusal to weight-bear is broad, but in the setting of focal tenderness over the calcaneus, the differential narrows to include etiologies that are infectious (cellulitis, osteomyelitis, septic arthritis), inflammatory (juvenile rheumatoid arthritis, reactive arthritis, seronegative spondyloarthropathies), neoplastic (osteochondroma), congenital/developmental (pes planus, tarsal coalition osteochondroses) and traumatic. In older children, overuse syndromes (e.g., bursitis, tendinitis, stress fracture, plantar fasciitis) are also on the differential. Our patient was afebrile with only minimally increased inflammatory markers, but his symptoms of focal tenderness and limp elicited concern for an infectious etiology. The only pertinent positive finding was the small fluid collection deep to the Achilles tendon. After revisiting all of the results, further history was obtained from the patient’s parents. It was discovered that the patient had been jumping on a hard surface the night prior to symptom onset and had been ‘stomping’ repeatedly in adult shoes. Based on the clinical history and radiologic evidence, a diagnosis of retrocalcaneal bursitis was made. Although the underlying pathophysiology of nonarticular soft tissue disorders continues to be investigated, overuse or repetitive activity and biomechanical conditions have been identified as predisposing conditions. It is postulated that an inflammatory process is likely part of the disease process. When evaluating a musculoskeletal condition, nonarticular disorders (e.g., bursitis, tendinitis) should first be distinguished from articular disorders. The presence of localized swelling and tenderness, greater limitation of active compared to passive motion, and absence of crepitus favor nonarticular processes. Bursitis syndromes can be subdivided into infectious and noninfectious variants. Infectious bursitis is usually due to transcutaneous entry of bacteria from microtrauma or a penetrating injury, or hematogenous spread. The skin overlying an infected bursa is often warm and edematous, and an abrasion or puncture site may be visualized. Inflammatory markers are often elevated, and the patient may be febrile. Noninfectious bursitis is more common in the context of overuse or repetitive activity. The subacromial and trochanteric bursae are most frequently affected (1). Retrocalcaneal bursitis is characterized by inflammation of the fluid-filled retrocalcaneal bursa located between the Achilles tendon insertion and calcaneous. It is most often noninfectious and results from overuse and repetitive loading. Thus, it is most commonly seen in adult runners and growing athletes. It has not been previously reported in the toddler age group. Presenting symptoms include focal tenderness and pain with active motion of the ankle, along with inflammatory signs such as local swelling and erythema. Laboratory investigations are often unremarkable. Bursal fluid aspiration, if performed, reveals nonbloody, bland fluid with a white blood cell count < 500/mm3. Imaging with ultrasonography or MRI, although not necessary, may be helpful for a more accurate diagnosis (2). The treatment for retrocalcaneal bursitis is joint protection and regular nonsteroidal anti-inflammatory agents to alleviate inflammation of the bursa. In our patient, given the rare presentation, antibiotics were also empirically prescribed given the possibility of an overlying cellulitis or soft tissue infection, as well as the ongoing consideration for septic bursitis that is often difficult to differentiate from nonseptic bursitis. Considering the persistent plantar-flexion and impractical nature of limb rest in this active toddler, a below-the-knee cast was applied to ensure immobility. After 2 weeks the cast was removed. The toddler was able to weight-bear without pain, and resumed normal mobility. Repeat radiographs illustrated normal bony morphology with no ankle effusions. Long-term follow-up revealed normal gait with intermittent toe-walking. Outpatient physiotherapy was arranged to promote restoration of range of motion. Overuse syndromes, such as retrocalcaneal bursitis, should be considered in toddlers whose history is in keeping with repetitive loading or when other more common etiologies have been ruled out. Ultrasound and MRI imaging can provide valuable information regarding the anatomy and pathology of limb joints and surrounding structures. In toddlers for whom prescribed rest of a joint or limb is not feasible, casting may help to ensure immobility and prevent inappropriate weight-bearing.

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