Irritable Hip: A clinical syndrome of acute hip pain and limited movement in a child, requiring systematic evaluation to exclude serious pathology.

Common Causes by Age:

Key Principle: Transient synovitis is a diagnosis of exclusion - always rule out septic arthritis first.

Presenting Complaint:

• Duration of symptoms (hours vs days)
• Onset (sudden vs gradual)
• Pain character and location
• Weight-bearing status

Associated Features:

• Fever (measure temperature)
• Recent viral illness (supports transient synovitis)
• General wellbeing (eating, drinking, activity level)
• Night pain (red flag for malignancy)

Past History:

• Previous hip problems
• Recent trauma
• Immunocompromise
• Sickle cell disease

Red Flag History:

• High fever
• Rapid deterioration
• Systemically unwell
• Not eating/drinking

First Impressions:

• Sick vs well-appearing child
• Comfortable vs distressed at rest
• Position of comfort

Lying Position:

• Hip held in flexion, abduction, external rotation
• This position maximizes hip joint capsule volume
• Reduces intracapsular pressure

Standing/Walking (if possible):

• Willingness to weight-bear
• Antalgic gait (short stance phase)
• Trendelenburg gait

Can Child Weight-Bear?

• Non-weight-bearing is Kocher criterion
• Willingness improves prognosis
• Compare with other leg

Antalgic Gait:

• Shortened stance phase on affected side
• Quick off painful leg
• May lean toward affected side

Trendelenburg Gait:

• Pelvis drops on swing side
• Trunk lurches to stance side
• Suggests abductor weakness/inhibition

Stiff Hip Gait:

• No hip movement during swing
• Circumduction or hip hiking
• Suggests fixed or very painful hip

Test in This Order:

1. Log roll first (gentlest, most sensitive)
2. Flexion (usually least painful)
3. Abduction/Adduction
4. Internal rotation (most restricted in septic arthritis)
5. External rotation

Compare with Normal Side:

• Always compare ROM bilaterally
• Note any asymmetry
• Quantify restriction

Key Finding in Septic Arthritis: Marked restriction of ALL movements, especially internal rotation, with severe pain.

Spine:

• Discitis can present as hip pain
• Examine for spinal tenderness
• Assess spinal movement

Knee:

• Hip pathology can refer to knee
• "Knee pain = examine hip"
• Check knee examination is normal

Lymph Nodes:

• Inguinal lymphadenopathy
• Suggests infection

Skin:

• Look for rashes (reactive arthritis, JIA)
• Check for bruising (NAI, malignancy)
• Insect bites (reactive synovitis)

Blood Tests:

• FBC (WCC for Kocher criteria)
• ESR (for Kocher criteria)
• CRP (more sensitive for infection, some include as 5th criterion)
• Blood cultures (before antibiotics)

Imaging:

• X-ray pelvis AP and frog lateral: Rule out Perthes, SUFE
• Ultrasound hip: Detect effusion (sensitivity greater than 95%)

Second-Line:

• MRI: If diagnosis unclear
• Hip aspiration: USS-guided if 2 or more Kocher criteria

Aspiration Findings:

• Turbid/purulent = likely septic
• Clear yellow = likely transient synovitis
• Send for microscopy, culture, cell count

1. Observation: General appearance, position in bed, distress level
2. Temperature: Check actual temperature (Kocher criterion)
3. Weight-bearing: Observe if child will stand and walk
4. Gait: Antalgic, Trendelenburg, stiff-hip pattern
5. Log roll: Most sensitive test - do first
6. ROM: Flexion, abduction, IR, ER - compare sides
7. Thomas test: Fixed flexion deformity
8. Spine: Tenderness, movement
9. Knee: Examine to exclude referred pain
10. Systemic: Lymph nodes, rash, general wellbeing