Hip Pathology Referred to Knee: Why Kids with Hip Problems Complain of Knee Pain
Referred Pain Patterns · 6 min read · 2026-02-28
The Classic Miss
A 12-year-old presents with a limp and complains of knee pain. The knee examination is normal. X-rays of the knee are normal. The child is sent home with "growing pains." Two weeks later, they return unable to bear weight — and the diagnosis is slipped capital femoral epiphysis (SCFE).
This scenario plays out repeatedly in emergency departments worldwide, and it is entirely preventable with one piece of anatomical knowledge.
The Obturator Nerve Connection
The hip joint is innervated by the obturator nerve (L2–L4), the femoral nerve, and the sciatic nerve. The obturator nerve also supplies sensory branches to the medial knee region. This shared innervation creates a referred pain pattern: pathology in the hip is perceived as pain in the knee.
This is not a rare curiosity — it is one of the most clinically important referral patterns in pediatric orthopedics.
Which Hip Conditions Present This Way?
- Slipped Capital Femoral Epiphysis (SCFE): The most dangerous miss. Common in overweight adolescents age 10–16. Knee pain with a limp and limited hip internal rotation.
- Legg-Calvé-Perthes Disease: Avascular necrosis of the femoral head in children age 4–10. Presents with a painless limp that progresses to knee or groin pain.
- Septic Arthritis of the Hip: Medical emergency. The child may be febrile and refuse to bear weight, but point to the knee.
- Transient Synovitis: Self-limiting hip inflammation, but must be distinguished from septic arthritis.
The Clinical Rule
Any child with knee pain and a normal knee examination must have their hip examined. This is non-negotiable.
The hip exam should include:
- Log roll test (most sensitive for hip irritability)
- Internal rotation range (restricted early in SCFE)
- FABER test (Flexion, Abduction, External Rotation)
- Gait assessment
Why Students Miss It
Students are taught to examine the joint that hurts. The patient points to the knee, so the student examines the knee. The knee is normal, and the student is reassured. The critical error is failing to examine the joint above and below — a fundamental principle that is easy to forget under pressure.
Clinical Pearl
In any child with an unexplained limp, always obtain an AP pelvis and frog-leg lateral X-ray of BOTH hips, regardless of where the child reports pain. SCFE is bilateral in up to 25% of cases.
Summary
Knee pain in a child with a normal knee = examine the hip. The obturator nerve connects these two joints, and hip pathology — especially SCFE — is a diagnosis you cannot afford to miss.