The limping child due to transient synovitis of the hip joint (toxic synovitis)
The approach to the limping child is complex and difficult to write up. There are so many reasons, each of another source.
However, there’s a diagnosis that is relatively common in pediatrics, that’s worthwhile for parents to be familiar with its characteristics.
There are many names for transient synovitis of the hip such as toxic synovitis, although there’s nothing toxic about this disease.
So, read more and learn.
What is synovitis and what does it have to do with the hip joint?
The synovia is a tissue that covers some of the body’s joints, one of which is the hip joint. Its purpose is to cover the joint and produce nourishing and lubricating substances. Synovitis is an inflammation of this tissue and when there’s an inflammation and secretion of inflammatory fluid into the joint and this joint starts to hurt.
What is transient synovitis of the hip joint in children?
In the pediatrics text book this disease appears in the chapter of Rheumatology (diseases of joints), in a chapter called ‘Reactive and post infectious arthritis’. Thus, it can be inferred that this disease is caused after exposure to certain infections.
For example, the child encounters a virus that only causes a common cold and recovers. The body tried to fight the virus, cause an immune reaction against the virus but in fact created antibodies that cause an inflammatory reaction in one of the joints. This is ‘Reactive and post infectious arthritis’.
If we aspirate that fluid and analyze it, we will not find the virus, but rather demonstrate the body’s immune system response against this infection that caused the common cold two weeks ago.
What are the main pathogens that begin this chain reaction in children?
Usually, pathogens that cause mild upper respiratory viral infection in the two weeks preceding the limp. In many of the cases, the parents hadn’t noticed or don’t remember that such an infection occurred.
What is the typical clinical manifestation?
The typical ages are three to eight years and the disease is more common in boys than girls. Children usually complain of pain in the hip joint area or the hip itself, and the child starts to limp abruptly on the affected leg. Note that the leg does carry weight. This is in contrast to conditions in which the child will stand in stork position.
Usually there is of-course no history of injury and no fever of 38 degrees and above.
The pain and limp may be more significant during some hours of the day and almost disappear in others. At times, there might be a worsening in the evening after a day that the child has been active.
Sometimes it’s hard for parents to decide which is the problematic leg and which leg is the limping one. Well, it’s possible to ask the child to walk and the leg on which the child lingers less (skips quickly over), is the problematic one. For example, if the inflammation is in the left hip, then the child will limp and make a quicker movement while stepping on the left foot, as compared with a full and longer movement on the right foot.
This disease lasts several days, a week on average, but may proceed longer too.
If we were to take lab test in a child with transient synovitis, they will show low inflammatory markers.
If we were to perform an x-ray or ultrasound we would discover at times excess fluid in the joint capsule, that indicates inflammation.
But more important than blood tests or imaging is to refer to the pediatrician for an examination.
How will the pediatrician diagnose transient synovitis?
Truthfully? Almost at the early stage of describing the history of the present illness.
A child in the right age with a mild-moderate limp. No high fever or other red flags. On examination there’s a limp on one of the legs and no swollen joints or painful areas on bones that may indicate injury. During the physical examination, when the child is lying face up, the physician will examine the lower body including both legs. Customarily the examination begins with the non-painful limb to avoid pain and resistance of the examined child. At the end of the exam, the physician will reach the hip joint and will preform a movement called ‘internal rotation’ that will cause the child to startle. Internal rotation is the rotation of this joint (hip) inward.
Sometimes the pain is so mild that it’s necessary to look very closely at the face of the examined child, to identify the small grimace.
Lab tests? Are not required in most cases.
X-ray or pediatric orthopedic surgeon? Reserve for cases in which the diagnosis is unclear.
However, tour pediatrician must be professional and experienced in the diagnosis of this condition, because there are other diseases that should not be missed.
What should not be missed in the limping child?
Of-course, other important diagnoses.
Injuries – mainly fractures or sprains. There are fractures in children, that I might describe on the web-site one day, that are very difficult to diagnose (e.g., greenstick fracture), and experience is needed to suspect and diagnose. Read more here on the signs of fractures in children.
Infections – mainly deep infections of bone or joint. One must remember that during a bacterial infection of the joint the child will usually look sicker and will have fever. However, not all children have read the medical book. A bacterial infection must not be overlooked because appropriate and timely treatment is necessary.
Other diseases – there are countless other, rarer diseases that may cause a limp in children.
The experienced physician will have all of these alternative diagnoses pass through their mind and will reject them one by one, until remains only with transient synovitis.
What is the treatment of transient synovitis?
As this is an inflammatory process, anti-inflammatory drugs are appropriate, mainly NSAIDS (Ibuprofen) I recommend treatment twice a day for three days, and then gradual reduction. Normally, improvement is immediate, although after withdrawal of treatment the limp often comes back a little.
Rest? Yes and no. If the child is in pain and limping, better to rest. On the other hand, children (and muscles and bones) need to move, so I would perhaps wait with track and field, but there’s no reason to avoid going to school/kindergarten.
Most importantly, as in many other pediatric diseases, diagnose this condition with your pediatrician, and trust them that other important things are not missed.
Be patience, and the child will get well. If this proceeds over two weeks, return to your physician for a repeat evaluation.
Good luck.
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