Irritable hip syndrome, also known as acute transient synovitis is a common cause of acute hip pain in children and there is swelling of tissues around the hip joint. It is one the most common hip joint disorders which is usually present at birth (congenital hip disorders). In most cases just one hip is affected. Irritable hip occurs in children before puberty. Boys are affected two to four times as often as girls. It commonly occurs about two weeks after a viral illness, especially of the upper respiratory tract. Sometimes the child may experience pain that spreads from the hip to the groin, thigh and knee. It does not usually last long, hence the term transient. However, the symptoms of pain and limping may alarm parents and guardians.
The main symptom of irritable hip syndrome in children is pain in one of the hips. The pain isn't usually severe, but it may prevent the child from placing weight on the affected leg, and it may cause them to limp. Occasionally, a child with irritable hip may also complain about additional pain in their knee or thigh, or restricted movement in one of the hip joints. In younger children who are unable to speak, the only noticeable symptom may be them crying at night. Sometimes, a child with irritable hip will have a slightly higher temperature than normal. Normal body temperature for a child is about 37ºC (98.6ºF).
Irritable hip occurs when the synovial membrane in the hip area becomes irritated and inflamed. All of the body's joints have a thin layer of delicate tissue that lubricates the joint and helps it to move. The layer of tissue is called the synovial membrane. Exactly what causes the membrane to become irritated and inflamed is unclear.
Some cases of irritable hip occur after a child has had a viral infection of their chest, throat or digestive system. As a result of this, many experts think that the synovial membrane in the hip becomes inflamed as a complication of the infection. However, there is no hard evidence to support this theory. Another theory is that a hip injury may cause the swelling, although many cases develop in children who do not have a history of injury.
Most children with irritable hip can be treated at home using a combination of painkillers and bed rest.
Painkillers: The non-steroidal anti-inflammatory drug (NSAID) called ibuprofen is the painkiller that's usually recommended to treat hip pain. Ibuprofen should help to relieve pain, reduce inflammation and speed up your child's recovery. Aspirin is not given to children who are under 16 years old because it can trigger a serious condition called Reye's syndrome, which can cause brain and liver damage. Massaging the affected hip and applying heat may also help to reduce the child's hip pain.
Bed rest: Bed rest is recommended until the symptoms of pain resolve, which usually takes around 7 to 10 days.
Hospital admission: The child may be admitted to hospital if diagnosis is uncertain or painkillers and bed rest haven't eased the pain. Further tests may be given to rule out an infection inside the hip joint (septic arthritis).
These tests may include:
It usually takes a fortnight to recover from irritable hip, although your doctor may recommend that the child does not play sport or take part in any strenuous activities for at least another two weeks following treatment. This is to reduce the chance of irritable hip returning. Swimming is a good way to strengthen the joint and get it moving again.