The Limping Child: A Systematic Approach to Diagnosis

JEFFREY R. SAWYER; MUKESH KAPOOR

JEFFREY R. SAWYER, MD, AND MUKESH KAPOOR, MD

A more recent article on evaluating the child with a limp is available.

Am Fam Physician. 2009;79(3):215-224

Author disclosure: Nothing to disclose.

Deviations from a normal age-appropriate gait pattern can be caused by a wide variety of conditions. In most children, limping is caused by a mild, self-limiting event, such as a contusion, strain, or sprain. In some cases, however, a limp can be a sign of a serious or even life-threatening condition. Delays in diagnosis and treatment can result in significant morbidity and mortality. Examination of a limping child should begin with a thorough history, focusing on the presence of pain, any history of trauma, and any associated systemic symptoms. The presence of fever, night sweats, weight loss, and anorexia suggests the possibility of infection, inflammation, or malignancy. Physical examination should focus on identifying the type of limp and localizing the site of pathology by direct palpation and by examining the range of motion of individual joints. Localized tenderness may indicate contusions, fractures, osteomyelitis, or malignancy. A palpable mass raises the concern of malignancy. The child should be carefully examined because nonmusculoskeletal conditions can cause limping. Based on the most probable diagnoses suggested by the history and physical examination, the appropriate use of laboratory tests and imaging studies can help confirm the diagnosis.

A normal mature gait cycle consists of the stance phase, during which the foot is in contact with the ground, and the swing phase, during which the foot is in the air. The stance phase is further divided into three major periods: the initial double-limb support, followed by the single-limb stance, then another period of double-limb support.¹

The gait undergoes orderly stages of development. Walking velocity, step length, and the duration of the single-limb stance increase with age, whereas the number of steps taken per minute decreases. A mature gait pattern is well established by three years of age, and the gait of a seven-year-old child closely approximates that of an adult.²

Clinical recommendation	Evidence rating	References
The following clinical features are more predictive of septic arthritis than of transient synovitis: Oral temperature > 101.3° F (38.5° C) Refusal to bear weight on affected leg ESR > 40 mm per hour Peripheral white blood cell count > 12,000 cells per mm³ (12.0 × 10⁹ cells per L) CRP level > 2.0 mg per dL (20.0 mg per L)	C	⁵
The initial imaging modality for a limping child who has focal findings on physical examination is anteroposterior and lateral radiography of the involved site.	C	²⁹
The initial imaging modality for a limping child who has no focal findings on physical examination is radiography of both lower extremities.	C	²⁹
Ultrasonography is recommended over plain-film radiography for detecting hip effusion.	C	³²
A bone scan is recommended for detecting underlying pathology when other imaging modalities have failed.	C	^33–36
When infection, inflammatory arthritis, or malignancy is suspected, a complete blood count with differential and measurement of ESR and CRP level should be obtained.	C	^23–25, ³³, ⁴⁶

Abnormal Gait

Abnormal gait can be antalgic or nonantalgic. An antalgic gait, which is characterized by a shortening of the stance phase, is a compensatory mechanism adopted to prevent pain in the affected leg. Because there is decreased contact between the affected leg and the ground, a child with such a gait may not report pain. There are several different types of nonantalgic gait (Figure 1); most of these do not require urgent evaluation and treatment.

The incidence of limping in children is unknown. One study of children presenting to an emergency department for an acute atraumatic limp reported a rate of 1.8 per 1,000 children younger than 14 years, a male-to-female ratio of 1.7:1, and a median age of 4.4 years.³ The limb involved (right or left) was nearly equal, and 80 percent of the children reported pain. Transient synovitis was the most common diagnosis.

Diagnosis

Limping in a child can have a variety of etiologies (Table 1). A detailed history and physical examination, in addition to appropriate laboratory tests and imaging, are essential for making a correct diagnosis (Figure 1 and Figure 2^4–6).

Bone conditions
Benign neoplasm
	Osteoblastoma
	Osteoid osteoma
Congenital condition
	Clubfoot
	Congenitally short femur
	Developmental dysplasia of the hip
Developmental condition
	Legg disease
	Slipped capital femoral epiphysis
Infection
	Osteomyelitis
Limb length discrepancy
Malignant neoplasm
	Ewing sarcoma
	Leukemia
	Osteosarcoma
Osteonecrosis
	Sickle cell disease
Overuse injury
	Osteochondritis dissecans
	Stress fracture
Trauma
	Child abuse
	Fracture (toddler’s fracture)
Intra-abdominal conditions
Appendicitis
Neuroblastoma
Psoas abscess
Intra-articular conditions
Congenital condition
	Discoid lateral meniscus
Hemarthrosis
	Hemophilia
	Trauma
Infection
	Gonorrhea
	Lyme disease
	Septic arthritis
Inflammation
	Acute rheumatic fever
	Juvenile rheumatoid arthritis
	Reactive arthritis
	Systemic lupus erythematosus
	Transient synovitis
Trauma
	Intra-articular injury
Neuromuscular conditions
Cerebral palsy
Meningitis
Muscular dystrophy
Myelomeningocele
Soft tissue conditions
Congenital condition
	Idiopathic tight Achilles tendon
Infection
	Cellulitis
	Pyomyositis or viral myositis
	Soft tissue abscess
Overuse injury
	Chondromalacia patellae
	Jumper’s knee
	Osgood-Schlatter disease
	Sever disease
Trauma
	Child abuse
	Foreign body
	Sprains and strains
Spinal conditions
Diskitis
Spinal cord tumors
Vertebral osteomyelitis

HISTORY

A thorough history should be obtained from the child and parents. In some cases, such as when child abuse is suspected, the child and parents should be interviewed separately. The initial history should be structured to determine the presence and nature of pain, history of trauma, and associated systemic signs (Table 2). Isolated musculoskeletal pain in the absence of other signs or symptoms is almost never a presenting symptom in children with chronic arthritis.⁷ Malignant bone tumors can present with intermittent pain at rest, which often misleads physicians into believing the condition is temporary and benign.⁸ The presence of systemic symptoms such as fever, weight loss, night sweats, and anorexia is highly suspicious for infection, inflammation, or malignancy.

Sign or symptom	Possible cause
Acute onset of pain	Fracture
Associated abdominal pain	Acute abdomen
	Neuroblastoma
	Psoas abscess
Associated back pain	Diskitis
	Spinal cord tumors
	Vertebral osteomyelitis
Associated fever, anorexia, weight loss, night sweats	Malignancy
	Osteomyelitis
	Rheumatologic disorder
	Septic arthritis
Associated neck pain, photophobia, or fever	Meningitis
Burning pain	Nerve involvement
Constant pain	Infection
	Malignancy
Focal pain	Fracture
	Infection
	Malignancy
Gradually worsening pain	Malignancy
	Osteomyelitis
	Rheumatologic disorder
	Stress fracture
History of bleeding disorder	Hemarthrosis
History of insect bite	Lyme disease
History of preceding diarrhea	Reactive arthritis
History of preceding pharyngitis	Acute rheumatic fever
History of trauma	Fracture
	Intra-articular injury
	Soft tissue injury
Intermittent pain at rest	Malignancy
Migratory polyarthralgia	Acute rheumatic fever
	Gonococcal arthritis
Morning stiffness	Rheumatologic disorder
	Stress fracture
Pain improves with activity	Rheumatologic disorder
Pain worsens with activity	Overuse injury
	Stress fracture
Pain in morning or after inactivity	Rheumatologic disorder
Pain at night	Malignancy
Radiating pain	Nerve or spinal cord involvement
Sexually active child	Gonococcal arthritis
	Reactive arthritis

PHYSICAL EXAMINATION

The main goals of the physical examination are to identify the type of limp and, if possible, to localize the site of pain (Table 3).

Finding	Possible cause
Abdominal mass	Neuroblastoma Psoas abscess
Abdominal tenderness	Acute abdomen
Asymmetrical gluteal and thigh skin folds	Developmental dysplasia of the hip
Calf hypertrophy	Muscular dystrophy
Conjunctivitis, enthesitis, oligoarthritis, urethritis	Reactive arthritis
Erythema chronicum migrans	Lyme disease
Erythema marginatum	Rheumatic fever
External hip rotation with hip flexion	Slipped capital femoral epiphysis
Galeazzi sign	Limb-length discrepancy
Hepatomegaly, lymph-adenopathy, splenomegaly	Malignancy Rheumatologic disorder
Hip joint flexed, abducted, externally rotated	Hip joint effusion (position maximizes joint volume and relieves pain)
Joint swelling	Hemophilia Inflammatory arthritis Reactive arthritis Septic arthritis
Localized bony tenderness	Contusion Fracture Malignancy Osteomyelitis
Loss of hip abduction	Developmental dysplasia of the hip
Loss of hip internal rotation	Legg disease Slipped capital femoral epiphysis
Malar rash	Systemic lupus erythematosus
Muscular arthropathy	Disuse muscular atrophy Neurologic disorder
Neck pain and stiffness, Brudzinski and Kernig signs	Meningitis
Non-weight bearing, painful limitation of range of motion	Septic arthritis
Obesity	Slipped capital femoral epiphysis
Overlying warmth or redness	Inflammatory arthritis Osteomyelitis Septic arthritis
Painless, nonpruritic maculopapular or vesicular skin rash, polyarthritis, tenosynovitis	Gonococcal arthritis
Palpable bony mass	Malignancy
Positive Patrick (FABER) test	Sacroiliac joint pathology
Positive pelvic compression test	Sacroiliac joint pathology
Positive Trendelenburg test	Developmental dysplasia of the hip Weak hip abductors
Psoas sign	Appendicitis Psoas abscess

Limp Type. Gait is best examined by having the child walk and run while he or she is distracted. Each limb segment should be observed systematically through several gait cycles. The stance and swing phases should be compared in both legs, and the range of motion of each joint should be evaluated. Upper body posturing and frontal plane abnormalities (e.g., scoliosis, varus and valgus deformities) should be noted. Differentiating between antalgic and nonantalgic gait and identifying the specific type of nonantalgic gait (Figure 1) help narrow the differential diagnosis.

Site of Pathology. The child should be unclothed during the examination. The resting limb position should be noted, and both sides should be compared for symmetry; areas of erythema, swelling, and deformity should be noted. The legs should then be palpated to localize the point of maximal tenderness and to detect any masses. Range of motion should be assessed in each joint, especially the hip (Figure 3 and Figure 4⁹). Joints adjacent to the painful one should be examined to rule out referred pain. This is especially important for hip conditions, which can present as knee or lateral thigh pain,⁴ leading to delayed diagnosis.¹⁰

Tests: The Trendelenburg test can be used to identify conditions that cause weakness in the hip abductors. The child stands on the affected limb and lifts the unaffected limb from the floor. In a positive test, the pelvis fails to stay level and drops down toward the unaffected side.

The Galeazzi sign can signal conditions that cause a leg-length discrepancy. The child should lie in the supine position with the hips and knees flexed. The test is positive if the knee on the affected side is lower than that on the normal side (Figure 5).

The Patrick test (also called the FABER test; Figure 6) can indicate pathology of the sacroiliac joint. With the child in the supine position, the examiner flexes, abducts, and externally rotates the hip joint. In a positive test, pain occurs in the sacroiliac joint.

The pelvic compression test also can indicate the presence of sacroiliac joint pathology. With the child in the supine position, the examiner compresses the iliac wings toward each other. Pain with this maneuver indicates sacroiliac joint pathology.

The psoas sign can signal a psoas abscess or appendicitis. With the child lying on his or her side, the hip is passively extended. Pain with hip extension indicates a positive test.

Special attention should be paid to performing a thorough spinal, pelvic, neurologic, abdominal, and genitourinary examination. Conditions affecting these systems are associated with limping (Table 1).

LABORATORY TESTS

A complete blood count with differential and measurement of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels should be obtained when infection, inflammatory arthritis, or malignancy is suspected. If septic arthritis is suspected, joint fluid should be aspirated urgently for Gram stain, culture, and cell count. Blood cultures should be obtained when infection is suspected, and bone cultures should be obtained in patients with suspected osteomyelitis. The role of specific laboratory testing is summarized in Table 4.^11–28

Test	Condition	Expected finding	Comments
ANA	SLE	Positive	Present in 94 percent of children with SLE¹¹; a negative ANA test virtually rules out SLE.¹²
			The test’s predictive value is low in most nonspecialty settings; most positive results do not indicate SLE.¹³
			Ten to 40 percent of healthy children can have a positive test.^12,14
			Test can be positive in patients with other medical conditions (e.g., infection, malignancy, other autoimmune conditions).^13,15
			A titer between 1:160 and 1:320 offers the best combination of high sensitivity and high specificity.¹²
			A positive test by itself is not diagnostic for SLE; three additional criteria must be present.¹⁶
			Test is of no diagnostic utility in ruling in or ruling out juvenile rheumatoid arthritis.¹⁷
ASO	Acute rheumatic fever	Increased ASO titers	Indicates true infection rather than carriage.
			Elevated ASO titers are found in up to 80 percent of patients with acute rheumatic fever.¹⁸
			Sensitivity can be further increased by testing for additional antibodies.¹⁸
Blood culture	Infection	Positive	Test is positive in 30 to 60 percent of patients with osteomyelitis¹⁹ and in 40 to 50 percent of patients with septic arthritis.²⁰
Bone culture	Osteomyelitis	Positive	Test is positive in 48 to 85 percent of patients with osteomyelitis.¹⁹
Bone culture	Osteomyelitis	Positive	Staphylococcus aureus is the most common pathogen isolated.¹⁹
CBC	Infection	Increased WBCs and platelets	WBC count is neither sensitive nor specific for infection, inflammation, or malignancy.
	Inflammation	Increased WBCs and platelets	Blast cells, lymphocytosis, and neutropenia may be seen in patients with leukemia.²¹
	Malignancy	Cytopenia²²	Cytopenia may occur in patients with SLE.¹¹
Coagulation profile	Known hemophilia or hemorrhagic effusion	Increased activated partial thromboplastin time	—
CRP	Infection	Increased CRP levels	Test is neither sensitive nor specific for infection, inflammation, or malignancy.
	Inflammation	Increased CRP levels	The negative probability of septic arthritis is 87 percent when CRP level is > 1 mg per dL (10 mg per L).²³
	Malignancy	Increased CRP levels	In patients with osteomyelitis and septic arthritis, CRP levels should rapidly normalize after initiation of therapy. A persistently elevated CRP level after the initiation of antibiotics indicates a poor response to therapy.^24,25
ESR	Infection	Increased ESR	Test is neither sensitive nor specific for infection, inflammation, or malignancy.
	Inflammation	Increased ESR	The negative probability of septic arthritis is 85 percent when ESR is > 25 mm per hour.²³
	Malignancy	Increased ESR	A low or normal platelet count in the presence of an elevated ESR suggests malignancy.²²
Lyme titer	Lyme disease	Positive	All children who live in or have recently traveled to an area endemic for Lyme disease should be tested.²⁶
Synovial fluid analysis	Septic arthritis	Turbid synovial fluid; WBC count > 50,000 to 100,000 per mm³; PMNs > 75 percent²⁷	—
Synovial fluid analysis	Transient synovitis	Clear yellow synovial fluid; WBC count 5,000 to 15,000 per mm³; PMNs < 25 percent²⁷
Synovial fluid culture	Septic arthritis	Positive	Test is positive in 50 to 80 percent of patients with septic arthritis.²⁰
Synovial fluid culture	Transient synovitis	Negative	S. aureus is the most common pathogen isolated in patients with septic arthritis.²⁷
Throat culture	Acute rheumatic fever	Group A hemolytic streptococci	Positive in only 10 to 33 percent of patients with acute rheumatic fever.¹⁸
Urethral, cervical, pharyngeal, and rectal cultures	Gonococcal arthritis	Neisseria gonorrhoeae	—
Urethral and stool cultures	Reactive arthritis	Chlamydia in urethral cultures²⁸; Salmonella, Shigella, Yersinia, and Campylobacter in stool cultures²⁸	—

IMAGING

Imaging should begin with standard orthogonal radiographs of the area of concern.²⁹ When imaging the hip, frog-leg lateral radiographs should always be obtained (Figure 7). The exception is in patients with suspected acute slipped capital femoral epiphysis, in whom a true lateral view of the hip should be obtained because a frog-leg view can cause exacerbation of the slip.³⁰ In children with a nonfocal clinical examination, and in those who are too young to localize pain or give a reliable history, the entire lower legs should be imaged.²⁹ Initial radiographs may be normal in children with stress fractures, toddler’s fracture,³¹ Legg disease, osteomyelitis, or septic arthritis.

Ultrasonography is highly sensitive for detecting effusion in the hip joint, but it cannot differentiate between sterile, purulent, or hemorrhagic fluid accumulations.³² If an effusion is seen in the hip joint and the clinical suspicion for septic arthritis is high, urgent ultrasound-guided aspiration should be performed, and the joint fluid should be sent for Gram stain, cell count, and culture. In such circumstances, aspiration must not be delayed.³³ If ultrasonography is not available, aspiration of the hip can be performed under fluoroscopic guidance. If neither of these imaging modalities is available, blind needle aspiration of the hip joint can be performed, but it carries a risk of injury to the femoral and obturator neurovascular structures, and the proper location of the needle cannot be confirmed. Blind needle aspiration should be performed only by experienced physicians when neither sonographic nor fluoroscopic guidance is available.

Bone scintigraphy is an excellent test for evaluating a limping child when the history, physical examination, and radiographic and ultrasound findings fail to localize the pathology.^33–36 Bone scanning allows the entire skeleton to be imaged simultaneously and is useful for detecting occult fractures, stress fractures, osteomyelitis, tumors, and metastatic lesions. Although it has a high sensitivity, this imaging modality lacks specificity.

Computed tomography (CT) is indicated when cortical bone must be visualized.³³ Magnetic resonance imaging (MRI) gives excellent visualization of joints, soft tissues, cartilage, and medullary bone.³³ Unlike bone scanning, MRI has both high sensitivity and specificity. It is especially useful for confirming osteomyelitis^37,38 (Figure 8), delineating the extent of malignancies, identifying stress fractures,^39,40 and diagnosing early Legg disease.^41–43 Fifteen to 63 percent of patients with slipped capital femoral epiphysis have involvement of the contralateral hip,⁴⁴ and MRI is useful for diagnosing “pre-slips” in these patients.⁴⁵

Common Diagnostic Dilemmas

SEPTIC ARTHRITIS VS. TRANSIENT SYNOVITIS OF THE HIP

Children with transient synovitis often are afebrile, appear nontoxic, and have less acute pain and range-of-motion restriction in the hip than those with septic arthritis, who typically appear toxic and have pain with movement of the joint in any direction. However, differentiating the two conditions can be difficult. A recent study used an oral temperature of greater than 101.3°F (38.5°C), refusal to bear weight on the affected leg, ESR greater than 40 mm per hour, peripheral white blood cell count of more than 12,000 cells per mm³ (12.0 × 10⁹ cells per L), and a CRP level greater than 2.0 mg per dL (20.0 mg per L) as predictors to distinguish between the two conditions.⁵ The probability of having septic arthritis was 37 percent with one predictor present, 63 percent with two, 83 percent with three, 93 percent with four, and 98 percent with all five predictors. Hip aspiration is the gold standard for diagnosing septic arthritis and should be performed whenever septic arthritis is suspected, because the sequelae of a missed or late diagnosis can be severe.⁴⁶

DISKITIS VS. VERTEBRAL OSTEOMYELITIS

Children with diskitis or vertebral osteomyelitis can present with a fever, back pain, or a limp, or they may refuse to walk. Although fever is present in both conditions, it is much more common, usually higher, and of longer duration in children with vertebral osteomyelitis.⁶ Children with diskitis usually do not appear ill, whereas those with vertebral osteomyelitis have a toxic appearance. In addition, diskitis involves the lumbar region almost exclusively, whereas vertebral osteomyelitis can involve any part of the spine. Radiographs of children with diskitis may show disk space narrowing and variable degrees of destruction of adjacent vertebral end plates; in children with vertebral osteomyelitis, localized rarefaction of one vertebral body and bony destruction may be seen. MRI is the diagnostic study of choice in children with suspected vertebral osteomyelitis.

MALIGNANCIES VS. RHEUMATOLOGIC DISEASES

Children with malignancies or rheumatologic conditions can have overlapping clinical features, such as musculoskeletal pain, fever, fatigue, weight loss, heaptomegaly, and arthritis.²² Nonarticular bone pain, back pain, bone tenderness, severe constitutional symptoms, night sweats, ecchymoses, bruising, abnormal neurologic signs, and abnormal masses are suggestive of malignancy.²² An elevated ESR in the presence of a normal or low platelet count also is worrisome for malignancy.²² One study found that in children presenting with unexplained musculoskeletal symptoms, a history of nighttime pain and the presence of a low white blood cell count and a low to normal platelet count has a sensitivity of 100 percent and a specificity of 85 percent for the diagnosis of acute lymphocytic leukemia.⁴⁷

PSOAS ABSCESS VS. SEPTIC ARTHRITIS

Children with a psoas abscess commonly present with a limp and pain around the hip. Differentiating a psoas abscess from septic arthritis of the hip can be challenging. Patients with a psoas abscess may have a palpable abdominal mass and a positive psoas sign. Because of the proximity of the psoas abscess to the spine and the peripheral nerves, scoliosis, sciatica, and femoral nerve neuropathy may be present.⁴⁸ Unlike children with septic arthritis, in whom range of motion is painfully limited in all directions, flexing the hip of a child with a psoas abscess relieves the pain and allows painless internal and external rotation of the hip. Plain-film radiography in children with psoas abscess may show obscuration of the sacroiliac joint; CT or MRI can be used to confirm the diagnosis.

Chambers HG, Sutherland DH. A practical guide to gait analysis. J Am Acad Orthop Surg. 2002;10(3):222-231.

Sutherland DH, Olshen R, Cooper L, Woo SL. The development of mature gait. J Bone Joint Surg Am. 1980;62(3):336-353.

Fischer SU, Beattie TF. The limping child: epidemiology, assessment and outcome. J Bone Joint Surg Br. 1999;81(6):1029-1034.

Matava MJ, Patton CM, Luhmann S, Gordon JE, Schoenecker PL. Knee pain as the initial symptom of slipped capital femoral epiphysis: an analysis of initial presentation and treatment. J Pediatr Orthop. 1999;19(4):455-460.

Caird MS, Flynn JM, Leung YL, Millman JE, D’Italia JG, Dormans JP. Factors distinguishing septic arthritis from transient synovitis of the hip in children. A prospective study. J Bone Joint Surg Am. 2006;88(6):1251-1257.

Fernandez M, Carrol CL, Baker CJ. Discitis and vertebral osteomyelitis in children: an 18-year review. Pediatrics. 2000;105(6):1299-1304.

McGhee JL, Burks FN, Sheckels JL, Jarvis JN. Identifying children with chronic arthritis based on chief complaints: absence of predictive value for musculoskeletal pain as an indicator of rheumatic disease in children. Pediatrics. 2002;110(2 pt 1):354-359.

Widhe B, Widhe T. Initial symptoms and clinical features in osteosarcoma and Ewing sarcoma. J Bone Joint Surg Am. 2000;82(5):667-674.

Storer SK, Skaggs DL. Developmental dysplasia of the hip. Am Fam Physician. 2006;74(8):1310-1316.

Kocher MS, Bishop JA, Weed B, et al. Delay in diagnosis of slipped capital femoral epiphysis. Pediatrics. 2004;113(4):e322-e325.

Ferraz MB, Goldenberg J, Hilario MO, et al. Evaluation of the 1982 ARA lupus criteria data set in pediatric patients. Committees of Pediatric Rheumatology of the Brazilian Society of Pediatrics and the Brazilian Society of Rheumatology. Clin Exp Rheumatol. 1994;12(1):83-87.

Malleson PN, Sailer M, Mackinnon MJ. Usefulness of antinuclear antibody testing to screen for rheumatic diseases. Arch Dis Child. 1997;77(4):299-304.

Shmerling RH. Autoantibodies in systemic lupus erythematosus—there before you know it. N Engl J Med. 2003;349(16):1499-1500.

Hilário MO, Len CA, Roja SC, Terreri MT, Almeida G, Andrade LE. Frequency of antinuclear antibodies in healthy children and adolescents. Clin Pediatr (Phila). 2004;43(7):637-642.

Covini G, von Mühlen CA, Pacchetti S, Colombo M, Chan EK, Tan EM. Diversity of antinuclear antibody responses in hepatocellular carcinoma. J Hepatol. 1997;26(6):1255-1265.

Tan EM, Cohen AS, Fries JF, et al. The 1982 revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum. 1982;25(11):1271-1277.

McGhee JL, Kickingbird LM, Jarvis JN. Clinical utility of antinuclear antibody tests in children. BMC Pediatr. 2004;4:13.

Jansen TL, Janssen M, van Riel PL. Grand rounds in rheumatology: acute rheumatic fever or post-streptococcal reactive arthritis: a clinical problem revisited. Br J Rheumatol. 1998;37(3):335-340.

Song KM, Sloboda JF. Acute hematogenous osteomyelitis in children. J Am Acad Orthop Surg. 2001;9(3):166-175.

Sucato DJ, Schwend RM, Gillespie R. Septic arthritis of the hip in children. J Am Acad Orthop Surg. 1997;5(5):249-260.

Tuten HR, Gabos PG, Kumar SJ, Harter GD. The limping child: a manifestation of acute leukemia. J Pediatr Orthop. 1998;18(5):625-629.

Cabral DA, Tucker LB. Malignancies in children who initially present with rheumatic complaints. J Pediatr. 1999;134(1):53-57.

Levine MJ, McGuire KJ, McGowan KL, Flynn JM. Assessment of the test characteristics of C-reactive protein for septic arthritis in children. J Pediatr Orthop. 2003;23(3):373-377.

Kallio MJ, Unkila-Kallio L, Aalto K, Peltola H. Serum C-reactive protein, erythrocyte sedimentation rate and white blood cell count in septic arthritis of children. Pediatr Infect Dis J. 1997;16(4):411-413.

Unkila-Kallio L, Kallio MJ, Eskola J, Peltola H. Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hematogenous osteomyelitis of children. Pediatrics. 1994;93(1):59-62.

Willis AA, Widmann RF, Flynn JM, Green DW, Onel KB. Lyme arthritis presenting as acute septic arthritis in children. J Pediatr Orthop. 2003;23(1):114-118.

Frank G, Mahoney HM, Eppes SC. Musculoskeletal infections in children. Pediatr Clin North Am. 2005;52(4):1083-1106.

Petersel DL, Sigal LH. Reactive arthritis. Infect Dis Clin North Am. 2005;19(4):863-883.

Myers MT, Thompson GH. Imaging the child with a limp. Pediatr Clin North Am. 1997;44(3):637-658.

Loder RT. Controversies in slipped capital femoral epiphysis. Orthop Clin North Am. 2006;37(2):211-221.

Halsey MF, Finzel KC, Carrion WV, Haralabatos SS, Gruber MA, Meinhard BP. Toddler’s fracture: presumptive diagnosis and treatment. J Pediatr Orthop. 2001;21(2):152-156.

Miralles M, Gonzalez G, Pulpeiro JR, et al. Sonography of the painful hip in children: 500 consecutive cases. AJR Am J Roentgenol. 1989;152(3):579-582.

Flynn JM, Widmann RF. The limping child: evaluation and diagnosis. J Am Acad Orthop Surg. 2001;9(2):89-98.

Aronson J, Garvin K, Seibert J, Glasier C, Tursky EA. Efficiency of the bone scan for occult limping toddlers. J Pediatr Orthop. 1992;12(1):38-44.

Diagnostic imaging referral guidelines: a guide for physicians. Canadian Association of Radiologists. http://www.caep.ca/CMS/get_file.asp?id=1e8819076bfd4021b8e80ee46e254c1a&ext=.pdf&name=CAR-ReferralGuidelines-e.pdf. Accessed July 28, 2007.

American College of Radiology appropriateness criteria. Limping child—ages 0–5 years. http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria/pdf/ExpertPanelonPediatricImaging/LimpingChildUpdateinProgressDoc6.aspx. Accessed July 28, 2007.

Stöver B, Sigmund G, Langer M, Brandis M. MRI in the diagnostic evaluation of osteomyelitis in children. Eur Radiol. 1994;4(4):347-352.

White PM, Boyd J, Beattie TF, Hurst M, Hendry GM. Magnetic resonance imaging as the primary imaging modality in children presenting with acute non-traumatic hip pain. Emerg Med J. 2001;18(1):25-29.

Gaeta M, Minutoli F, Scribano E, et al. CT and MR imaging findings in athletes with early tibial stress injuries: comparison with bone scintigraphy findings and emphasis on cortical abnormalities. Radiology. 2005;235(2):553-561.

Ishibashi Y, Okamura Y, Otsuka H, Nishizawa K, Sasaki T, Toh S. Comparison of scintigraphy and magnetic resonance imaging for stress injuries of bone. Clin J Sport Med. 2002;12(2):79-84.

Kaniklides C, Lönnerholm T, Moberg A, Sahlstedt B. Legg-Calvé-Perthes disease. Comparison of conventional radiography, MR imaging, bone scintigraphy and arthrography. Acta Radiol. 1995;36(4):434-439.

Lahdes-Vasama T, Lamminen A, Merikanto J, Marttinen E. The value of MRI in early Perthes’ disease: an MRI study with a 2-year follow-up. Pediatr Radiol. 1997;27(6):517-522.

Lamer S, Dorgeret S, Khairouni A, et al. Femoral head vascularisation in Legg-Calvé-Perthes disease: comparison of dynamic gadolinium-enhanced subtraction MRI with bone scintigraphy. Pediatr Radiol. 2002;32(8):580-585.

Aronsson DD, Loder RT, Breur GJ, Weinstein SL. Slipped capital femoral epiphysis: current concepts. J Am Acad Orthop Surg. 2006;14(12):666-679.

Futami T, Suzuki S, Seto Y, Kashiwagi N. Sequential magnetic resonance imaging in slipped capital femoral epiphysis: assessment of preslip in the contralateral hip. J Pediatr Orthop B. 2001;10(4):298-303.

Frick SL. Evaluation of the child who has hip pain. Orthop Clin North Am. 2006;37(2):133-140.

Jones OY, Spencer CH, Bowyer SL, Dent PB, Gottlieb BS, Rabinovich CE. A multicenter case-control study on predictive factors distinguishing childhood leukemia from juvenile rheumatoid arthritis. Pediatrics. 2006;117(5):e840-e844.

Song J, Letts M, Monson R. Differentiation of psoas muscle abscess from septic arthritis of the hip in children. Clin Orthop Relat Res. 2001(391):258-265.