The most common causes of non-traumatic hip or inguinal pain in growing children are transient synovitis of the hip, Perthes disease, slipped upper femoral epiphysis and overuse injuries of pelvic ossification centres.
Rare, but serious aetiologies of hip pain requiring emergency treatment are leukaemia, tumours and septic arthritis/osteomyelitis.
Transient synovitis of the hip
Symptoms and findings
The most common cause of a sudden limp and refusal to walk in children between 3 and 10 years of age.
This is an aseptic inflammation of the joint capsule of the hip.
The child refuses to bear weight on the limb, complains of pain in the hip, thigh or knee, and holds the thigh in a flexed position and externally rotated with the knee bent. Hip rotation and extension are limited.
ESR may be slightly elevated.
An ultrasound examination of the hip will reveal possible effusion in the hip joint.
X-ray findings will be normal. X-rays are not necessarily indicated in early disease but should always be taken if symptoms persist for more than 2 weeks and when the patient is older than 10 years.
Differential diagnosis
Another diagnosis is likely and further investigations are warranted if
the symptoms have persisted for longer than two weeks
the patient is under 2 or over 10 years of age
the patient has fever or general symptoms
CRP is higher than 20 mg/l or ESR higher than 35 mm/h.
If symptoms persist for a longer time, further examinations should be done in specialized care.
Perthes disease
Circulatory disturbance of unknown aetiology involving the femoral head and causing bone fragility and hip pain.
Patients are typically boys between 5 and 9 years of age (the disease is 4 times more common in boys than in girls).
Symptoms and findings
Symptoms usually develop gradually and fluctuate.
Limping gait
Pain in the groin, thigh or knee
ESR, CRP and blood leukocyte count are normal.
Diagnosis is based on X-raying: irregularity and consolidation of the subchondral bone structure is noted initially, followed by a decrease in the size of the femoral head in comparison with the unaffected side.
Treatment, follow-up and prognosis
Perthes disease should be treated and followed up in specialized care, in a paediatric orthopaedic unit. Urgent (not emergency) referral is indicated.
The circulatory disturbance makes the femoral head more fragile. To prevent this, the load acting on the bone should be reduced.
Lighter exercise (such as swimming, cycling) should be used to maintain the range of hip motion and muscle strength.
The need for surgical treatment is assessed case by case.
The prognosis depends on the child's age at diagnosis and the extent of the circulatory disturbance.
The prognosis for functional recovery is usually good in children below 6 years of age.
Slipped upper femoral epiphysis (SUFE)
Definition
The femoral head, or epiphysis, slides into a displaced position in relation to the femoral neck.
Onset may be acute or gradual.
Symptoms and diagnosis
The typical patient is an overweight child of 11 to 16 years of age with delayed puberty.
The disease is about twice as common in boys as in girls.
The patient has a limp and holds the limb in external rotation.
The clinical picture may be acute, with the pain starting suddenly, and the patient may not be able to place any weight on the limb.
The patient may describe the pain as being located in the groin, thigh or knee.
The diagnosis is based on X-raying. The shift can best be seen in the Lauenstein projection that should always be taken.
Treatment
The situation is equivalent to femoral neck fracture: the patient should be referred as an emergency case to a paediatric orthopaedic unit.
Operative treatment is required, primarily closed reduction and screw fixation.
Patients run an about 10-20% risk of subsequent contralateral SUFE. Therefore, prophylactic fixation of the contralateral asymptomatic hip should be considered.
If the diagnosis is delayed, the femoral head may become ossified in a malposition, and open surgery will be needed to fix this. Such procedures involve a significant risk of circulatory disturbance in the femoral head and should be concentrated to specialized paediatric orthopaedic units (e.g. at university hospitals).
Overuse injuries of pelvic ossification centres, or apophysitis
These conditions typically occur during the pubertal growth spurt, sometimes earlier.
They occur at the attachment sites of large muscle tendons, which are cartilaginous structures in children.
Nouri A, Walmsley D, Pruszczynski B, et al. Transient synovitis of the hip: a comprehensive review. J Pediatr Orthop B 2014;23(1):32-6 [PubMed]
Cook PC. Transient synovitis, septic hip, and Legg-Calvé-Perthes disease: an approach to the correct diagnosis. Pediatr Clin North Am 2014;61(6):1109-18 [PubMed]