25 Pain in the Lower Extremity and Limping in Children
The physician should approach leg pain or limp in children as in adults—that is, determine whether it originates in joints or soft tissue. The most common causes of childhood leg pain originating in the soft tissue are unusual or strenuous exercise and trauma. Fractures constitute the most common cause of acute limp in children. Other common causes of leg pain are growing pains, Legg-Calvé-Perthes disease (epiphysitis of the hip), Osgood-Schlatter disease (an abnormality of the epiphyseal ossifi cation of the tibial tubercle), chondromalacia patellae, and ossification of the Achilles insertion. Limping can be due to pain, weakness, or structural abnormality. It is important to determine the duration and progression of the limp, history of trauma, nature of pain, and any weakness and to observe the gait.
If a limp occurs when a young child begins to walk, congenital dislocation of one or both hips should be considered. Toddler’s fracture, an undisplaced fracture of the distal tibia, may occur when weight bearing first occurs (9 months to 3 years). It may manifest as a limp or the inability to bear weight on the affected leg. In 1- to 5-year old patients, other common causes of limp include toxic synovitis, septic arthritis or osteomyelitis, developmental abnormalities, and juvenile rheumatoid arthritis. In 5- to 10-year-old patients, the more common causes are trauma, toxic synovitis, and infectious joint or bone disease. Legg-Calvé-Perthes disease (epiphysitis of the hip) usually occurs between ages 5 and 7 years. In patients 10 to 15 years old, slipped femoral epiphyses and patellar problems are more common. In children between ages 10 and 12, pain in the heel is most often caused by painful bursitis or irregular ossification of a calcaneal apophysis.
Growing pains is a general diagnosis that is being made less frequently as physicians become more expert in making specific diagnoses. However, growing pains do exist, and they are now thought to be a form of myalgia. The aching pain is intermittent and usually located in the leg muscles, particularly in the front of the thigh, the calf, and the back of the knee. The pain is deep and localized to areas outside the joints. It is usually bilateral and typically occurs late in the day, although it may awaken the child from a sound sleep. Growing pains may be exacerbated by excessive running during the day, but exercise is not usually a factor. The findings that the pain is nonarticular, bilateral, and usually unrelated to activity are essential to the accurate diagnosis of growing pains. Children with growing pains show no abnormal physical findings.
Most serious diseases that cause leg pain in children (except slipped capital femoral epiphyses) are usually unilateral. Pain in the hip may result from Legg-Calvé-Perthes disease, a disturbance of the epiphyseal ossification of the femoral head in children ages 4 to 12 (peak age, 5 to 7 years). It is often associated with a limp. The pain is occasionally referred to the medial aspect of the knee. Transient synovitis of the hip can result from an upper respiratory illness but must be differentiated from septic arthritis and osteomyelitis (both of which require early diagnosis and treatment with intravenous antibiotics). Juvenile rheumatoid arthritis (now called juvenile idiopathic arthritis) is diagnosed in a child with joint pain for longer than 6 weeks, and a joint effusion, stress pain, limited range of motion, or increased warmth.
The most common causes of knee pain in children are acute trauma, Osgood-Schlatter disease, and chondromalacia patellae. Osgood-Schlatter disease is an abnormality of the epiphyseal ossification of the tibial tubercle. It is most common in children 10 to 15 years old. This condition involves painful swelling of the tibial tubercle at the insertion of the patellar tendon. The pain is worse with contraction of the quadriceps against resistance. It is exacerbated by activity and relieved by rest.
Chondromalacia patellae is just one of several causes of anterior knee pain. (Some believe the term should be discarded, but its use is still commonplace.) It results from chronic patellofemoral dysfunction and is an extremely common syndrome in active children and adolescents. It may be a precursor of adult patellofemoral arthritis.With patellofemoral dysfunction, patellar cartilage degenerates, not because of primary cartilaginous disease but from abnormal mechanical forces acting on it.
These abnormal forces may result from direct or indirect trauma. Direct injury may occur when force is applied to the anterior aspect of the patella; this usually results from a fall on the flexed knee. Indirect trauma is more common and is usually the result of strenuous or repetitive quadriceps activity to which the patient is unaccustomed (e.g., hiking, jogging, calisthenics, skiing). The most characteristic symptom of indirect trauma is pain in the lower pole of the patella and adjacent patellar tendon that is precipitated by strenuous activity, especially running, jumping, and squatting. After resting with the knee flexed, patients with indirect trauma experience a marked increase in pain when they initially extend the knee and begin to move around, but they usually find some relief after standing still or walking a short distance. Patients often describe a grating sensation that may be detected on physical examination when the knee is flexed and extended. The grating is noted particularly when the knee is extended against resistance. Radiographic findings are usually normal but may include fragmentation of the lower pole of the patella.
Chondromalacia patellae must be differentiated from patellar osteochondritis, jumper’s knee, and partial rupture of the patellar tendon. Children with chondromalacia patellae usually have localized tenderness at the lower pole of the patella and the adjacent patellar tendon (see Fig. 24-2). The physician may occasionally note separation of the patellar tendon from the lower pole and a palpable defect at that point.
Other conditions that give rise to knee pain are patellar subluxation, patellar dislocation, and meniscal injuries. Although they are uncommon, rheumatoid arthritis and popliteal cysts can occur in children.
Limping is a common complaint among children. It is never normal, although its causes are many, ranging from poorly fitting shoes to a sprained ankle to the earliest manifestation of a malignant tumor. To determine the exact cause of limping, the physician must approach the problem methodically and thoroughly, obtaining a detailed history and performing a careful examination of the child’s gait.