The Limping Child: A Systematic Approach to Diagnosis



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Am Fam Physician. 2009 Feb 1;79(3):215-224.

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

SORT: KEY RECOMMENDATIONS FOR PRACTICE

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

3336

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

2325, 33, 46


CRP = C-reactive protein; ESR = erythrocyte sedimentation rate.

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to http://www.aafp.org/afpsort.xml.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

View Table

SORT: KEY RECOMMENDATIONS FOR PRACTICE

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

3336

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

2325, 33, 46


CRP = C-reactive protein; ESR = erythrocyte sedimentation rate.

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to http://www.aafp.org/afpsort.xml.

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.

Diagnosis of Children with a Nonantalgic Gait

Figure 1.

Diagnostic approach to a child with a nonantalgic gait. (CTEV = congenital talipes equinovarus; DDH = developmental dysplasia of the hip.)

View Large

Diagnosis of Children with a Nonantalgic Gait


Figure 1.

Diagnostic approach to a child with a nonantalgic gait. (CTEV = congenital talipes equinovarus; DDH = developmental dysplasia of the hip.)

Diagnosis of Children with a Nonantalgic Gait


Figure 1.

Diagnostic approach to a child with a nonantalgic gait. (CTEV = congenital talipes equinovarus; DDH = developmental dysplasia of the hip.)

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 246).

Table 1.

Differential Diagnosis of Limping in Children

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

Table 1.   Differential Diagnosis of Limping in Children

View Table

Table 1.

Differential Diagnosis of Limping in Children

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

Diagnosis of Children with an Antalgic Gait

Figure 2.

Diagnostic approach to a child with an antalgic gait. (CBC = complete blood count; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; MRI = magnetic resonance imaging; WBC = white blood cells.)

Information from references 4 through 6.

View Large

Diagnosis of Children with an Antalgic Gait


Figure 2.

Diagnostic approach to a child with an antalgic gait. (CBC = complete blood count; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; MRI = magnetic resonance imaging; WBC = white blood cells.)

Information from references 4 through 6.

Diagnosis of Children with an Antalgic Gait


Figure 2.

Diagnostic approach to a child with an antalgic gait. (CBC = complete blood count; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; MRI = magnetic resonance imaging; WBC = white blood cells.)

Information from references 4 through 6.

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.

Table 2.

Findings from Patient History That Suggest Possible Causes of Limping in Children

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

Table 2.   Findings from Patient History That Suggest Possible Causes of Limping in Children

View Table

Table 2.

Findings from Patient History That Suggest Possible Causes of Limping in Children

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).

Table 3.

Findings from Physical Examination That Suggest Possible Causes of Limping in Children

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

Table 3.   Findings from Physical Examination That Suggest Possible Causes of Limping in Children

View Table

Table 3.

Findings from Physical Examination That Suggest Possible Causes of Limping in Children

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

Figure 3.

Internal rotation of the hip is measured by placing the child in the prone position with knees flexed 90 degrees and rotating the feet outward. Loss of internal rotation is a sensitive indicator of intraarticular hip pathology and is common in children with Legg disease and slipped capital femoral epiphysis.

View Large


Figure 3.

Internal rotation of the hip is measured by placing the child in the prone position with knees flexed 90 degrees and rotating the feet outward. Loss of internal rotation is a sensitive indicator of intraarticular hip pathology and is common in children with Legg disease and slipped capital femoral epiphysis.


Figure 3.

Internal rotation of the hip is measured by placing the child in the prone position with knees flexed 90 degrees and rotating the feet outward. Loss of internal rotation is a sensitive indicator of intraarticular hip pathology and is common in children with Legg disease and slipped capital femoral epiphysis.

Figure 4.

Hip abduction is measured by placing the child in the supine position with hips and knees flexed and the toes placed together. To measure abduction, both knees are allowed to fall outward. Limited hip abduction, as in this child’s left hip, occurs in children with developmental dysplasia of the hip.

Reprinted with permission from Storer SK, Skaggs DL. Developmental dysplasia of the hip. Am Fam Physician. 2006;74(8):1313.

View Large


Figure 4.

Hip abduction is measured by placing the child in the supine position with hips and knees flexed and the toes placed together. To measure abduction, both knees are allowed to fall outward. Limited hip abduction, as in this child’s left hip, occurs in children with developmental dysplasia of the hip.

Reprinted with permission from Storer SK, Skaggs DL. Developmental dysplasia of the hip. Am Fam Physician. 2006;74(8):1313.


Figure 4.

Hip abduction is measured by placing the child in the supine position with hips and knees flexed and the toes placed together. To measure abduction, both knees are allowed to fall outward. Limited hip abduction, as in this child’s left hip, occurs in children with developmental dysplasia of the hip.

Reprinted with permission from Storer SK, Skaggs DL. Developmental dysplasia of the hip. Am Fam Physician. 2006;74(8):1313.

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).

Figure 5.

Positive Galeazzi sign. The child is placed in the supine position with the hips and knees flexed. In a positive test, the knee on the affected side is lower than the normal side. This can occur in patients with any condition that causes a leg-length discrepancy, such as developmental dysplasia of the hip, Legg disease, or femoral shortening.

View Large


Figure 5.

Positive Galeazzi sign. The child is placed in the supine position with the hips and knees flexed. In a positive test, the knee on the affected side is lower than the normal side. This can occur in patients with any condition that causes a leg-length discrepancy, such as developmental dysplasia of the hip, Legg disease, or femoral shortening.


Figure 5.

Positive Galeazzi sign. The child is placed in the supine position with the hips and knees flexed. In a positive test, the knee on the affected side is lower than the normal side. This can occur in patients with any condition that causes a leg-length discrepancy, such as developmental dysplasia of the hip, Legg disease, or femoral shortening.

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.

Figure 6.

The Patrick (FABER) test. Note how the examiner has flexed, abducted, and externally rotated the child’s right hip.

View Large


Figure 6.

The Patrick (FABER) test. Note how the examiner has flexed, abducted, and externally rotated the child’s right hip.


Figure 6.

The Patrick (FABER) test. Note how the examiner has flexed, abducted, and externally rotated the child’s right hip.

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 4.1128

Table 4.

Laboratory Tests for Diagnosis in a Limping Child

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

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

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

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


ANA = antinuclear antibodies; ASO = antistreptolysin O titer; CBC = complete blood count; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; PMN = polymorphonuclear neutrophils; SLE = systemic lupus erythematosus; WBC = white blood cell.

Information from references11 through 28.

Table 4.   Laboratory Tests for Diagnosis in a Limping Child

View Table

Table 4.

Laboratory Tests for Diagnosis in a Limping Child

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

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

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

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


ANA = antinuclear antibodies; ASO = antistreptolysin O titer; CBC = complete blood count; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; PMN = polymorphonuclear neutrophils; SLE = systemic lupus erythematosus; WBC = white blood cell.

Information from references11 through 28.

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.

Figure 7.

Frog-leg lateral radiograph of a patient with slipped capital femoral epiphysis. Note the slip in the patient’s right hip (arrow) compared with the normal left hip.

View Large


Figure 7.

Frog-leg lateral radiograph of a patient with slipped capital femoral epiphysis. Note the slip in the patient’s right hip (arrow) compared with the normal left hip.


Figure 7.

Frog-leg lateral radiograph of a patient with slipped capital femoral epiphysis. Note the slip in the patient’s right hip (arrow) compared with the normal left hip.

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.3336 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 osteomyelitis37,38 (Figure 8), delineating the extent of malignancies, identifying stress fractures,39,40 and diagnosing early Legg disease.4143 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

Figure 8.

Magnetic resonance image of a patient with osteomyelitis. Note the signal change within the bone marrow consistent with osteomyelitis (long arrow) and a subperiosteal abscess (small arrow). This patient had normal plain radiographs.

View Large


Figure 8.

Magnetic resonance image of a patient with osteomyelitis. Note the signal change within the bone marrow consistent with osteomyelitis (long arrow) and a subperiosteal abscess (small arrow). This patient had normal plain radiographs.


Figure 8.

Magnetic resonance image of a patient with osteomyelitis. Note the signal change within the bone marrow consistent with osteomyelitis (long arrow) and a subperiosteal abscess (small arrow). This patient had normal plain radiographs.

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.

The Authors

JEFFREY R. SAWYER, MD, FAAOS, FAAP, is an assistant professor of orthopaedic surgery at the University of Tennessee-Campbell Clinic, LeBonheur Children’s Medical Center, and St. Jude Children’s Research Hospital in Memphis, Tenn. He received his medical degree from the University of Rochester (NY) School of Medicine and Dentistry.

MUKESH KAPOOR, MD, is a recent graduate of the family medicine residency program at Advocate Lutheran General Hospital, Park Ridge, Ill. He received his medical degree from Madras Medical College, Chennai, India.

Author disclosure: Nothing to disclose.

Address correspondence to Jeffrey R. Sawyer, MD, University of Tennessee-Campbell Clinic, 1211 Union Ave., Suite 510, Memphis, TN 38104 (e-mail: jsawyer@campbellclinic.com). Reprints are not available from the authors.

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