Hip Pain

OVERVIEW

Hip pain is discomfort arising from the acetabulofemoral articulation or surrounding periarticular soft tissues (tendons, bursae, musculature, neurovascular structures).

Anatomical Mapping & Referral Patterns:

• Anterior / Groin Pain: Most specific for true intra-articular pathology (Osteoarthritis, Labral Tear, Femoroacetabular Impingement [FAI], Avascular Necrosis, Septic Arthritis).
• Lateral Hip Pain: Periarticular soft tissue pathology, predominantly Greater Trochanteric Pain Syndrome / gluteal tendinopathy.
• Posterior Hip / Buttock Pain: Referred pain from the lumbar spine (L4–S1 radiculopathy), sacroiliac joint, or deep gluteal syndrome (piriformis syndrome).

Knee pain is a classic referred presentation of hip pathology (via the obturator and femoral nerves); every patient presenting with isolated knee pain—especially children and adolescents—requires a mandatory hip examination.

TRIAGE & ALGORITHM

Step 1: Emergency Triage & Red Flag Screening

• Trauma + Inability to Bear Weight + Shortened & Externally Rotated Leg
  • -> Suspect Fractured Neck of Femur (#NOF). Immediate immobilization, orthogonal X-rays, analgesia, and urgent Orthopedic consult.
• Trauma + Flexed, Adducted, Internally Rotated Leg
  • -> Suspect Posterior Hip Dislocation (High-energy MVA; emergency closed reduction required within 6 hours to avoid avascular necrosis).
• Fever + Severe Inability to Bear Weight + Refusal to Tolerate Passive ROM
  • -> Suspect Septic Arthritis (Apply Kocher criteria in children; urgent joint aspiration required).
• Adolescent / Child with Limp or Isolated Knee/Thigh Pain:
  • -> Suspect Slipped Capital Femoral Epiphysis (orthopedic emergency: strict non-weight-bearing) or Perthes Disease.

Step 2: Anatomical Pain Localization

• Anterior Groin Pain
  • Worse with internal rotation/flexion (FADIR test positive): Labral Tear / FAI.
  • Chronic, activity-related, morning stiffness < 30 min: Hip Osteoarthritis.
  • High-dose corticosteroid use or alcohol excess: Avascular Necrosis (AVN).
• Lateral Hip Pain
  • Focal tenderness over greater trochanter, worse lying on affected side: Greater Trochanteric Pain Syndrome (GTPS) / Gluteal Tendinopathy.
• Posterior / Buttock Pain
  • Dermatomal radiation down the leg, positive straight leg raise: Lumbar Radiculopathy / Sciatica.

Step 3: Diagnostic Decision Branching

• Acute Traumatic Suspicion + Normal Plain Radiographs: -> Obtain an urgent MRI Hip (or CT Pelvis/Hip) to rule out an occult femoral neck fracture or stress fracture.
• Non-Traumatic Acute Monoarthritis: -> Urgent Ultrasound-guided hip aspiration to differentiate Septic Arthritis from Crystal Arthropathy.

DIFFERENTIAL DIAGNOSIS

Acute & Traumatic Emergencies

• Neck of Femur Fracture
  • Distinguishing features: Elderly, osteoporotic, minor fall; shortened and externally rotated lower limb; groin/hip pain on active straight leg raise and gentle axial loading.
• Septic Arthritis of the Hip
  • Distinguishing features: Rapid onset of severe groin pain, high fever, systemic toxicity, refusal to bear weight; joint held in flexion, abduction, and external rotation (position of maximal intracapsular volume); synovial WBC > 50,000 x 10^6/L with > 90% polymorphs.

Pediatric & Adolescent Hip Conditions

• Slipped Capital Femoral Epiphysis (SCFE / SUFE)
  • Distinguishing features: Overweight/obese adolescent (age 10–16); presents with an antalgic limp and dull ache referred to the thigh or knee; obligate external rotation during passive hip flexion; frog-leg lateral X-ray shows failure of Klein’s line to intersect the lateral epiphysis.
• Legg-Calvé-Perthes Disease (Avascular Necrosis of Femoral Epiphysis)
  • Distinguishing features: Boys aged 4–8 years; insidious painless or mildly painful limp; limited hip abduction and internal rotation; X-ray shows femoral head flattening, fragmentation, and sclerosis.
• Transient Synovitis (Irritable Hip)
  • Distinguishing features: Young child (age 3–8); mild limp following a viral URTI; child is afebrile or low-grade; inflammatory markers normal/mildly elevated; self-limiting within 7–10 days.

Chronic & Degenerative Intra-Articular Conditions

• Hip Osteoarthritis
  • Distinguishing features: Age > 50; insidious groin/anterior thigh pain; morning stiffness < 30 minutes; loss of internal rotation is the earliest clinical sign; weight-bearing X-ray shows joint space narrowing, subchondral sclerosis, osteophytes, and subchondral cysts.
• Femoroacetabular Impingement & Acetabular Labral Tears
  • Distinguishing features: Young active athletes; deep anterior groin pain provoked by prolonged sitting, pivoting, or deep squatting; positive FADIR test (Flexion, Adduction, Internal Rotation reproduces sharp pain).
• Avascular Necrosis (AVN / Osteonecrosis) of the Femoral Head
  • Distinguishing features: History of systemic steroid therapy, chronic alcohol excess, sickle cell disease, or previous trauma; progressive groin pain, normal early X-ray followed by the pathognomonic “crescent sign” (subchondral collapse) on plain film; MRI is gold standard.

• Extra-Articular / Soft Tissue Disorders:
  • Greater Trochanteric Pain Syndrome / Gluteal Tendinopathy:
    • Distinguishing features: Middle-aged females; lateral hip/thigh pain, point tenderness over the greater trochanter; pain aggravated by lying on the affected side, climbing stairs, or single-leg standing for 30 seconds.

INVESTIGATIONS

First-Line / Emergency Diagnostics

• Plain Radiographs (AP Pelvis + Dedicated Lateral of Affected Hip):
  • Adults: Weight-bearing AP Pelvis, cross-table lateral of affected hip (assesses fractures, osteoarthritis, AVN).
  • Pediatrics: AP Pelvis + Bilateral Frog-Leg Lateral (Dunlap) views (mandatory to detect subtle posterior displacement in SCFE).
• Inflammatory Markers & Bloods: FBC, ESR, CRP, Blood cultures (mandatory if septic arthritis or osteomyelitis is suspected).
• Diagnostic Ultrasound of the Hip: Evaluates hip joint effusion; guides urgent percutaneous arthrocentesis for synovial fluid Gram stain, culture, and crystal analysis.

Targeted / Specialized Imaging

• MRI Hip (Non-Contrast):
  • Indications: Gold standard for diagnosing occult femoral neck fractures, early Avascular Necrosis (before X-ray changes appear), stress fractures, osteitis pubis, and transient osteoporosis of the hip.
• MR Arthrogram (MRA Hip with Intra-Articular Gadolinium):
  • Indications: Diagnostic modality of choice for acetabular labral tears and articular cartilage defects.
• CT Pelvis / Hip: Best for defining complex acetabular fractures, preoperative planning for arthroplasty, or assessing bony morphology in FAI (cam/pincer lesions).

CRITICAL MANAGEMENT

Fractured Neck of Femur (#NOF):

• Emergency Resuscitation: Fast-track analgesia (Fascia Iliaca Compartment Block [FICB]), IV fluids, pressure area care.
• Early Surgical Fixation: Operative management within 24–48 hours (Cannulated screws for undisplaced intracapsular; Hemiarthroplasty / Total Hip Arthroplasty for displaced intracapsular; Cephalomedullary nail or Dynamic Hip Screw for extracapsular/intertrochanteric fractures).

Slipped Capital Femoral Epiphysis Emergency Protocol:

• Immediate Non-Weight-Bearing: Patient must NOT walk or bear any weight (admit directly to hospital in a wheelchair/bed).
• Urgent Surgical Pinning: Urgent in situ single cannulated screw fixation to prevent further slip progression and catastrophic avascular necrosis of the femoral head.

Septic Arthritis of the Hip

• Emergency Decompression: Immediate arthroscopic or open arthrotomy washout by Orthopedics.
• Empiric IV Antibiotics: Administer IV Flucloxacillin or Cefazolin (+ Vancomycin if MRSA suspected) only after synovial fluid aspiration has been performed.

Greater Trochanteric Pain Syndrome

• Conservative Therapy: Avoid aggressive stretching of the ITB; activity modification (avoid crossing legs, sleep with pillow between knees); targeted physical therapy focusing on isometric gluteal strengthening.
• Second-Line: Ultrasound-guided corticosteroid injection around the trochanteric bursa (short-term relief only; not a long-term cure).