PAINFUL HIP

Christopher G. Anton, MD

DIFFERENTIAL DIAGNOSIS

Common

Transient Synovitis
Septic Arthritis
Osteomyelitis
Slipped Capital Femoral Epiphysis (SCFE)
Legg-Calvé-Perthes (LCP)
Juvenile Idiopathic Arthritis (JIA)
Trauma

Less Common

Idiopathic Chondrolysis
Osteoid Osteoma
Osteonecrosis
Malignancy

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Age and history are helpful in narrowing differential diagnosis

Helpful Clues for Common Diagnoses

Transient Synovitis
- a.k.a. irritable hip, toxic synovitis
- Age: 18 months to 10 years; most common from age 4-7
- Typically follows recent upper respiratory infection
- Radiographs
  - Normal
  - Widening of medial joint space, lateral displacement of femoral head
- 70% hip effusion on ultrasound
- Hip held in flexion, external rotation, and abduction, restricted abduction and internal rotation
- ± fever (often < 38° C)
- May have mildly elevated erythrocyte sedimentation rate and white blood cell
- Symptoms improve (usually within 48 hours) in 1-5 weeks
  - If symptoms persists beyond 1 week, consider another diagnosis
  - Recur in up to 17%
  - Legg-Calvé-Perthes develops in 1-3%
Septic Arthritis
- Important to diagnose early to avoid destruction of joint
  - Delay in treatment ≥ 4 days results in suboptimal recovery
- Age: < 4 years old
- Staphylococcus aureus most common cause
  - Umbilical catheter, sepsis, and prior venous puncture have been implicated
- Hip held in flexion
- Infants can present with low-grade fever and feeding intolerance
- Radiographs
  - Normal
  - Periostitis of proximal femur in neonates within days after start of symptoms
- Treatment: Surgical drainage, IV antibiotics, traction
Osteomyelitis
- Staphylococcus aureus most common
- Streptococcus pneumonia (hypogammaglobinemia, sickle cell disease, asplenia)
- Referred pain from spine or sacroiliac joints
  - Importance of scrutinizing spine and sacroiliac joints when imaging hips
- May take up to 10-14 days before radiographs depict changes or osteomyelitis
- Treatment: Abscess drainage, debridement, IV antibiotics
Slipped Capital Femoral Epiphysis (SCFE)
- Salter-Harris type 1 femoral epiphyseal fracture
- Age: 10-15 years old
- M:F = 2:1; occurs earlier in girls
- Predisposed: Obesity and endocrine disorders
- Bilateral (18-36%)
  - Opposite side occurs within 18-24 months of 1st occurrence
- Presentations: Acute, chronic, and acute on chronic
- Radiographs
  - Widened femoral physis, medial and posterior displacement of femoral head (best seen frog leg lateral view)
  - Capital femoral epiphysis displacement without intersection of Klein line
  - Klein line: Line along lateral femoral neck and continuing toward acetabulum; ordinarily crosses small portion of femoral ossification center
Legg-Calvé-Perthes (LCP)
- Osteonecrosis of femoral head of unknown etiology
- Age: 3-12 years old; peak: 6-8 years old
- Bilateral (10-20%)
- Radiographs
  - Normal
  - Flattening, fragmentation, and sclerosis of femoral head
- Key: Prognosis heavily depends on containment of femoral head
Juvenile Idiopathic Arthritis (JIA)
- a.k.a. juvenile rheumatoid arthritis (JRA)
- Age: < 16 years old
- Symptoms with > 6 week duration
- Other causes of arthritis are excluded
- Stiff, swollen, painful, warm, and decreased motion in joint involved
- MR: Synovitis, ± erosions, ± rice bodies
- Joint space narrowing and ankylosis are late findings
Trauma
- Acute (fracture) or repetitive (stress fracture) trauma

Helpful Clues for Less Common Diagnoses

Idiopathic Chondrolysis
- Destruction of articular cartilage of femoral head and acetabulum
- Stiffness, limpness, and pain around hip
- Radiographs
  - Concentrically joint space narrowing, < 3 mm with osteopenia and pelvic tilt
- MR: Rectangular hypointense T1 and hyperintense T2WI signal abnormality of center 1/3 of femoral head, ± ill defined within acetabulum
Osteoid Osteoma
- Benign composed of osteoid and woven bone
- 3 types: Cortical (most common), cancellous, or subperiosteal
- < 2 cm nidus surrounded by dense sclerotic bone
- Most common location is femur
- Age: 10-30 years old, uncommon before age 5
- Classic history: Pain at night relieved by nonsteroidal anti-inflammatory agents
- NECT: Depicts nidus better than MR
- Bone scan: Increased flow, “double density” pattern
  - Intense uptake by nidus surrounded by less intense activity of reactive bone
Osteonecrosis
- Most commonly located in anterolateral weightbearing portion of femoral head
- T2WI: “Double line” sign
- Many causes, including sickle cell disease, trauma, steroid therapy, vasculitis, Gaucher disease, hemophilia
Malignancy
- Primary such as chondroblastoma
- Metastatic disease: Most commonly neuroblastoma
- ± pathologic fracture

Image Gallery

Longitudinal ultrasound shows a widened anechoic joint space

with a convex outer margin, consistent with a hip effusion. Note the synovial thickening

along the femoral neck and joint lining.

Longitudinal ultrasound shows a normal hip for comparison with no significant joint fluid, evidenced by a normal joint space with a concave anterior margin