Common Causes of Hip Pain in Children

The rapid diagnosis of hip pain is important to rule out joint or bone infection that left undiagnosed may lead to joint destruction.

Differential diagnosis of acute hip pain in children

  1. Infectious
    1. Septic arthritis of the hip
    2. Septic arthritis of the sacroiliac joint
    3. Lyme disease
    4. Osteomyelitis of femoral head or pelvis
    5. Psoas abscess
    6. Appendicitis or abdominal/pelvic abscess
  2. Inflammatory
    1. Transient synovitis
    2. Systemic arthritis
      1. Spondyloarthropathy
      2. Juvenile idiopathic arthritis (rare as isolated hip pain)
      3. Kawasaki disease
      4. Infectious/post-infectious
    3. Idiopathic chondrolysis of the hip
    4. Chronic recurrent multifocal osteomyelitis
  3. Mechanical/orthopedic
    1. Slipped capital femoral epiphysis (SCFE)
    2. Avascular necrosis
      1. Legg-Calve-Perthes disease
      2. Secondary avascular necrosis
    3. Femoral stress fracture
    4. Muscular strain
  4. Neoplastic/infiltrative
    1. Osetoid osteoma
    2. Leukemia
    3. Solid Tumor, primary or metastatic
    4.  Pigmented villonodular synovitis
  5. Other
    1. Sickle cell pain crisis

Epidemiology of common causes of hip pain

  1. Septic arthritis: typical age- any (peak 0-6 years); M:F ratio 1:1
  2. Transient synovitis: typical age- 3 to 8 years, mean 6 years; M:F ratio 2:1; mostly occurs in the fall and winter
  3. Perthes disease: typical age 3 to 12 years, peak 5 to 7; M:F ratio 4:1; rare in blacks
  4. Slipped capital femoral epiphysis: typical age early adolescence, mean 12 years for girls and 13.5 for boys; M:F ratio 1.5:1; obese children, endocrinopathy in 8%, blacks>whites, hispanics

Important Questions to Ask in the History

  1. Has there been fever, and how high has it been?
  2. Has there been a recent viral illness?
  3. Has there been any trauma?
  4. Has there been knee pain?
  5. Acute onset more suggestive of trauma or infection. How long has there been symptoms?
  6. Are there any underlying conditions? Sickle cell disease, rickets, SLE, Anorexia Nervosa, medications such as steroids.
  7. Is there a family history of hip disease?
  8. Tick exposure?
  9. Evidence of systemic disease: weight loss, pallor, fatigue, rash, bowel irregularity

Physical Examination

  1. Observe gait
  2. Check for leg length discrepancy
  3. Evaluate for muscle atrophy. This may suggest chronic disuse. 
  4. Is there point tenderness or evidence of joint swelling?
  5. Check range of motion.
  6. Examine the back

Diagnostic Studies: directed by the findings from the history and physical exam

  1. Acute severe process suspected: CBC w/diff, CRP, ESR, blood culture, arthrocentesis for synovial fluid Gram stain, culture, and WBD count w/diff
  2. Chronic or insidious onset: CRP or ESR (can differentiate between inflammatory from noninflammatory disease); Anemia, leucopenia, or thrombocytopenia may suggest underlying chronic illness (malignancy); HLA-B27 associated with spondyloarthropathy; Lyme serology is reasonable in the appropriate epidemiologic setting since Lyme arthritis can cause hip pain
  3. Radiographic evaluation: necessary in patients with suspected septic arthritis, skeletal injury, or tumor
    1. Plain radiographs can identify bony abnormalities, including some forms of trauma; tumors and other malignancies; advanced Leff-Calve-Perthes disease; SCFE
    2. Ultrasound can identify small joint effusions and should be used when plain radiographs are normal but the suspicion of septic arthritis or transient synovitis remains high
    3. MRI and CT used most often to pursue a cause of hip pain when other modalities have not been helpful or to provide more detail of an abnormality already identified
    4. Bone scan can differentiate septic arthritis or TS from osteomyelitis.  In more chronic case it can be used to identify avascular necrosis or Legg-Calve-Perthes disease earlier in the course than can a plain radiograph.  Bone scan can also help diagnose tumors and myelodysplastic disease.

Common Etiologies

  1. Septic hip joint
    1. Rapid diagnosis is imperative because increased pressure within joint may lead to decreased blood supply to the femoral head
    2. The majority of the children are less than four years of age. Present with acute onset of fever, pain, ill appearance, refusal to stand, limp. Infants may present with irritability and poor feeding. 
    3. Hip usually held in flexed and abducted position.
    4. Diagnosis is by combination of suspicion, physical findings, radiographic changes with widening of joint space, and obtaining fluid from a joint tap. Fluid will have low glucose, usually > 50,000 WBCs and a predominance of polys. Gram stain and culture will be positive in about 80% of the cases. 
    5. Blood culture positive in 20% of the cases. Most cases will have increased WBC count, CRP, and ESR. (temp >38.5 degrees C, ESR>40mm/h, WBC>12,000cell/mm3, CRP>2mg/dL)
    6. Treatment.- Surgical drainage and antibiotics to cover susceptible S. aureus. Further treatment determined by the organisms isolated and their sensitivity to antibiotics. 
  2. Osteomyelitis
    1. May have history of trauma
    2. Proximal femur is the most common site of osteo in children
    3. Fever and ill appearing, limp or refusal to stand, point tenderness.
    4. Increased ESR, CRP, and WBCs 
    5. Diagnosis by radiographs, bone scan, and needle aspiration obtaining organism. Bone scan has the advantatge of detecting multifocal disease, which occurs in 7 percent of cases of pediatric osteomyelitits, usually in neonates.
    6. Most common organism is S. aureus
  3. Toxic Synovitis
    1. Most common between 2-8 years of age. It is a benign condition with the presence of small amount of fluid in the joint. Often follows viral illness (32-50%). Etiology speculated to be post infectious reactive arthritis. It is important to rule out a bacterial infection of the joint and bone. 
    2. Child may refuse to stand and limp. There may be pain on maneuvering the hip joint. The child does not usually appear ill, absent or low grade fever, and the ESR, CRP, and WBC count are normal or slightly elevated. 
    3. Radiograph is normal or only small effusion present. Fluid is sterile. 
    4. Symptoms affect both hips in as many as 5 percent of cases.  In symptomatically unilateral disease, ultrasound can detect bilateral effusions in 25 percent of children
    5. Recurrence rates are 4 to 15 percent
    6. Treatment is reassurance and following carefully to be sure that there is no septic process, analgesics, and rest as needed. Lasts for a few days.  1-2% of cases may progress to Perthes disease with avascular necrosis of the ipsilateral femoral head
  4. Slipped Capital Femoral Epiphysis
    1. Males > females and most common 10 -16 years of age. May be bilateral (20-40%) and present at different times. This is a fracture of the growth plate leading to a slipping (posteriorly) of the femoral epiphysis off the femoral neck.
    2. Patient often overweight and there is an association with hypothyroidism.
    3. Patient complains of pain in hip or knee and holds the extremity externally rotated. Resists internal rotation.
    4. Radiograph positive. The femoral head is displaced medially in relation to the femoral neck. 
    5. Treatment is surgical with pinning of the joint.
  5. Legg Calve Perthe’s Disease
    1. This is an avascular necrosis of the femoral head. Common between the ages of 3-12 years (mean 7 years old) and greater incidence in males. 10% are bilateral 
    2. The onset is insidious with painless limp and then development of hip, groin, lateral thigh, or knee pain. Physical examination will demonstrate leg length discrepancy, decreased abduction and internal rotation. 
    3. Radiographic diagnosis. There is a flattening and fragmentation of the femoral head.
    4. Treatment is bracing or surgery.
  6. Osteoid Osteoma
    1. These are benign bone tumors, most common in the femur and tibia prior to adolescence.
    2. Pain is worse at night and responds dramatically to aspirin. Failure to respond to ASA usually rules out the diagnosis.
    3. May require CT scan or bone scan to demonstrate
    4. Surgical removal 
  7. Malignancy
    1. Rarely presents as arthritis.
    2. Neuroblastomas, leukemias (ALL most common cancer to present as joint pain in children), osteosarcomas, and Ewing’s sarcomas, Eosinophilic granulomas
    3. Pain at night, bone pain distant from the joint, anemia, leucopenia, LDH or uric acid can suggest leukemia
  8. Rheumotologic disorders
    1. Spondyloarthopathies-psoriatic arthritis.  Skin manifestations may be subtle, such as dryness behind the ears or nail pits.
    2. JIA- rarely presents with isolated hip disease
    3. Kawasaki disease
    4. Lyme diseasez
    5. Acute rheumatic fever
    6. Poststreptococcal arthritis
  9. Trauma
    1. Femor is the third most common site of stress fracture in children. 
    2. Pain commonly experienced in the anterior thigh.
    3. Plain films are usually negative early in the course of fracture.  Bone scan or MRI are the test of choice.
  10. Idiopathic chondrolysis of the hip
    1. Poorly defined condition in which articular cartilage of the hip is injured by an undefined inflammatory process.
    2. F>M, usually in second decade of life.  African-Americans are affected more severely.
    3. Biopsy reveals mild chronic inflammation and is helpful to exclude infection
    4. Some patients recover but some go on to develop painful and disabling osteoarthritis of the hip.
    5. Treatment with antiinflammatories seems helpful in some patients.

Reference

  1. Hollingsworth,P Differential Diagnosis and Management of Hip Pain in Childhood. British Journal of Rheumatology. 1995; 34: 78-82
  2. Elyn Palermo Theophilopoulos and Douglas Barnett. Get a grip on the pediatric hip. Contemporary Pediatrics November 1998
  3. Frick, SL. Evaluation of the child who has hip pain.  Orthop Clin North Am. 2006 Apr; 37(2):133-40
  4. Uptodate: “Overview of hip pain in childhood”

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