In growing children, increased circulation to the joint and the growing ends of the bone facilitates seeding of these areas with bacteria. Thus, most cases of osteomyelitis and septic joint are from hematogenous spread. Direct penetration of the joint or bone also may lead to infection. Finally, contiguous spread of infection from the bone to the joint has been documented, so providers should consider concomitant orthopedic infections in all cases. Children with blood disorders or other chronic constitutional illnesses will have a higher incidence of infection with more atypical bacteria.

Toxic synovitis probably represents a response by the joint mounted against a non-specific irritant such as blood-borne virus. The joint produces an abundance of fluid (effusion) and may show signs of inflammation (eg, pain, swelling, erythema), which may mimic acute infection. The fluid, however, is sterile. Aspiration of the fluid may be delayed if the examination is relatively benign (ie, no systemic toxicity, minimal pain on joint range of motion) and the child can be closely observed over a short period (from 4 to 6 days) for worsening symptoms.

Orthopedic infections demonstrate a bimodal incidence, with peak occurrence in the young and the very old or immunocompromised patients. The most frequently involved skeletal areas are those of most rapid growth: knee, elbow, hip, and heel. Slower growing bones such as the clavicle, scapula, and spine are less frequently involved (Dagan, 1993). The most frequent infective agent varies somewhat by age and clinical setting (see Table 44-1).

Toxic synovitis tends to occur in young boys between ages 3 and 6 years and usually in association with or closely following a viral infection. This self-limited illness tends to resolve completely without sequelae in 1 week. The etiology of this very common condition remains unknown.

Common history and physical findings are shown in Table 44-2.

In joint infection, radiographs may show effusion and in extreme cases, subluxation of a joint. The reader is referred to Figure 44-1. In neonates, apparent joint disruption may be the only clue to a septic arthritis. Ultrasound may be useful to confirm fluid in the joint. For osteomyelitis, specific radiographic changes include periosteal reaction and bone destruction. Please see Figure 44-2 for osteomyelitis in a 2-year old child.

Technetium Bone Scan will be positive with 90+% sensitivity in osteomyelitis but may be less sensitive for a septic joint (Morrissey, 1996). Because of the association between septic arthritis and bone infection, a bone scan is recommended even when joint infection is proven on aspiration.

CBC and differential will show increased white blood cell counts in most infections of the bone and joint but will be normal in toxic synovitis. ESR is generally elevated for infection, but is non-specific. Both CBC and ESR may be falsely negative in very young children. C-Reactive Protein may be more specific for orthopedic infections (Unkila-Kallio, 1994), but it is costly and not readily available in all settings. In the toxic child, blood cultures are mandatory and may have a high yield of identifying the infective organism. Depending on the child’s age and clinical condition, the clinician may need to perform a complete septic work-up.

In the face of high clinical suspicion of joint infection, aspiration of the joint fluid is essential. The provider must culture the fluid, perform Gram staining, and test for white blood cells. A white blood cell (WBC) count greater than 100,000 is felt to be diagnostic for a true bacterial infection. A WBC count between 50,000 to 75,000 may indicate arthritis, sympathetic effusion from an osteomyelitis, or possibly a less virulent joint infection. Lowered lactic acid and glucose in the joint fluid (compared to serum levels) are also indicative of infection.

The most important step in treatment is recognition of a potentially limb-threatening situation. Basic treatment strategies are described in Table 44-3. Since gram-positive organisms (staph and strep) predominate, currently recommended
antibiotic regimens are 2 weeks of intravenous (IV) treatment with 150 mg/kg/day of Oxacillin or Nafcillin divided every 6 hours, followed by 100 mg/kg/day of high-dose, oral Cephalexin divided every 6 hours for 4 weeks (Morrissey, 1996). Although quinolones such as ciprofloxacin may be more effective orally, these antibiotics are not used in children because of concern about growth arrest (Menschik, Neumuller, Steiner, et al., 1997). Joint arthritis is treated with 2 weeks of IV antibiotics alone. Clinicians should adjust all antibiotics according to cultures and sensitivities and response to treatment, as evidenced by symptom improvement and decreasing ESR. The treatment of toxic synovitis includes rest, reassurance, non-steroidal anti-inflammatory drugs (NSAIDs), and close daily follow-up, to ensure that the clinical course is one of gradual improvement.

Children with bone infections may have a prolonged hospitalization or home restriction during the treatment process. Home-nursing services may be necessary to assist with long-term antibiotics and wound care. Tutoring programs are often necessary if the infection occurs during the school year.

Growing pains are seen in children between ages 3 and 6. The incidence is difficult to assess since parents often do not bring their children to providers for evaluation when symptoms appear too mild.

Apophysitis tends to occur in older children (ages 11 years and older), although Sever’s may occur in younger children at the first major spurt in shoe size. Boys are affected for all apophysitides more frequently than girls (2:1). The most common type is OSD. One apophysitis may coexist with another (Tolo, 1996).

Growing pains will present as vague pain, usually poorly localized around both knees. Rarely, the child may voluntarily limit activities. The pain will often respond to massage and analgesics such as NSAIDs or acetominophen. Constitutional symptoms should always be absent. Physical exam generally is non-focal, with no point tenderness, joint disruption,
or gait disturbance. Any positive findings should point to another diagnosis.

The clinical picture of apophysitis is that of pain that worsens with activity, although pain may be present at rest if inflammation is significant. The pain may respond to NSAIDs and ice or heat, but relief is generally limited and short. Apophysitis always features point tenderness over the inflamed portion of the limb. In OSD the anterior shin will be markedly tender and prominent with mild erythema and swelling. There may be a limp, and range of motion of the knee will be painful, especially with extension and extension against resistance. “Jumper’s knee” can be differentiated by tenderness over the lower pole of the patella, with no significant swelling or bony prominence. Knee straightening may be painless, but resisted bending will often elicit symptoms. Sever’s disease involves tenderness over the back of the foot, directly at the end of the heel bone. There may be a reddened, prominent area with increased warmth locally as in OSD. Children will have difficulty standing on their toes but complain of most pain when duck or heel walking.

If the clinical picture is classic for either growing pains or true apophysis, extensive laboratory or radiographic testing may not be necessary. If there is a history of trauma or any systemic illness, providers should obtain x-rays of the limb (or limbs) to rule out fracture, infection, or another less common entity.

For growing pains, x-rays and laboratory studies are by definition negative and unnecessary unless the pain persists for an extended period. Radiographs of the painful area in OSD or other apophysitis will show elevation and widening of the growth plate and possibly fragmentation of the bone. It may be difficult to differentiate OSD from acute fracture of the tibial tubercle.

Growing pains will almost always respond to gentle massage, ice or heat, and occasionally analgesics. Gentle stretching may be useful, particularly in long-standing cases. Episodes will typically be of limited duration, lasting no more than 6 to 9 months, and recurrence is extremely unusual. If the pain is persistent, or if it worsens in the face of other clinical findings, the provider should evaluate the child with a complete work-up including x-rays, bone scan, and screening labs. The clinician should evaluate the child with persistent episodes of waking from sleep for possibly non-orthopedic etiology, such as night terrors or recurrent muscular spasm.

Treatment of apophysitis includes anti-inflammatory doses of NSAIDs, gentle stretching, and short-term activity modification. Bracing can be helpful, with a patellar-stabilizing (“donut hole”) sleeve knee brace for OSD or “jumper’s knee” and heel wedges for Sever’s disease. In severe cases, the child may need short-term casting to allow the inflammation to completely resolve. Although by definition all apophysitis will resolve at the cessation of growth, early aggressive treatment is advocated to minimize the painful course and to allow as quick a return to normal activity as possible. As with growing pains, recurrence is highly unusual.

Although most cases of apophysitis and growing pains can be treated at the primary care level, clinicians should refer recalcitrant cases for further evaluation and possibly more aggressive therapy. Providers should reassure parents and children that the pain is self-limited and will resolve with conservative care, but that any bony deformity is permanent.