Thursday, 24 September 2015

What's wrong with this child's legs?

Normal legs (Part 1 of a series of paediatric orthopaedic posts)

When I was newly a father, my own grandmother scolded me for bouncing my son on his feet when he was a few months old.  Apparently, I would give him “bandy legs” and cripple him for life.  What I now know is that bandy legs were a normal part of how children grow, not a medical problem.  In fact the vast majority of what happens to children’s legs are a normal part of development.  However. like most things in medicine, these presentations can be an orthopaedic problem in disguise.  This post will explore what (in general) is normal and how to spot what is not.

Much of the time, children’s legs seem to be a 'funny shape'.  As a general rule, things start to point out, then in and then straighten up as a child grows into their adult body.  

Fig 1. From birth, children's knees will tend to go into varus and then valgus before becoming a normal adult shape.  Bandy legs (also called bow legs) are therefore expected in a child under the age of three and knock knees are considered normal until roughly 8 years old.  Genu valgum may persist into adolescence without any need for intervention.

There are some general rules that help the clinician to know that a child's legs are normal.

Similarly, there are some indications that there is a genuine problem

In general terms, the following presentations are normal unless there is reason to think otherwise (see red flags above):
  • Knock knees, in a child up to the age of 3 years or up to the age of 10 if resolving .
  • In-toeing gait with knees that are also internally rotated.
  • Flat feet on weight bearing.
  • Tip toe walking in toddlers
  • Hypermobility
  • 'Growing pains'
The term Growing pains is a misnomer since there is no proven link between episodes of pain and periods of increased growth.  It is true that children roughly between the ages of 3 and 12 get unexplained episodes of lower limb pains.

These are all common problems which can either be the reason for attending primary care (including emergency departments, walk-in centres etc.) or asked about as an aside when a child attends for another problem.  The lovely thing about all of them is that the history and examination required is usually brief.  It is rare to need to refer or investigate.  What's wrong with  this child's legs?  Usually nothing, but more on that story next week...

Edward Snelson
The Hitchcock of Free Open Access Medical Education

Disclaimer:  I turns out that I was causing my son to have limb problems.  He is now unfeasibly tall.

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