Free Material


Clinicians regularly use outcome measures to monitor changes in the children in their care and help to demonstrate evidence based practice. One of the most common measures used for children with cerebral palsy is the Gross Motor Function Measure (GMFM), an internationally recognised, standardised and validated measure. This evaluative tool provides information about a child’s functional skills at a specific point in time and gives information about abilities relative to other children with cerebral palsy.

The Motor Development Curves combined the GMFM and Gross Motor Function Classification System (GMFCS), enable evaluation of functional skills relative to the average for a child’s age and GMFCS Level.  The tabulated reference percentiles*, as graphical data, are available on-line meaning that clinicians can make a more accurate review of a child’s progress. These tables provide information at 0, 3, 6 and 9 months for each year from 2 years to 12 years 0 months with GMFM scores enabling identification of every 5th percentile from 5th to 95th with the addition of the 3rd and 97th percentile.

*Percentiles are most commonly seen in the standard height and weight charts used to monitor growth in childhood. The percentiles referred to here, monitoring functional change, work in exactly the same way.

The Optimi Percentile Calculator has further developed this work by creation of a tool that accurately calculates the percentile, rather than relying on specifying a point on a printed graph. It requires only the child’s date of birth, GMFCS Level, date of assessment and GMFM score to be entered. Data can also be entered for several GMFM assessments of the same child over time. A graph is then produced which can be printed and filed or stored electronically (Please observe local Data Protection rules).

This work was therefore to develop a system extending the use of Reference Percentiles to numerically calculate the percentile and to be able to present the mean percentile change over a course of therapy/intervention so that individual and group results can be easily and accurately determined.

This system also enables easier comparison of clinical outcomes in children with cerebral palsy between physiotherapists, between departments and possibly even between countries. It is recognised that the GMFM is a measure based on therapeutic strategies in use some years ago and today’s practice may be quite different. However, GMFM remains in widespread use and retains value.

Clinicians will naturally wish to see an increase in GMFM score in the children in their care, although recognising from the Motor Development Curves that there may be some plateauing or even some reduction in abilities with increasing age, depending on a child’s GMFCS Level. Caution must be used when interpreting percentile comparisons since the expected within-child variability in percentiles is substantial. Clinicians should also be aware that an increase in GMFM score does not necessarily equate with an increase in percentile! A child may be performing more activities but still falling behind comparable children in same GMFCS Level.

Take a look at these example percentile graphs.


Look at the GMFM-66 data for this child.  As you can see, the scores are gradually increasing as the child grows but does this report on how they are doing compared to their peers?  Advance the slide to see the percentile comparison.

Here we see the same tabulated data with the percentile calculated and plotted on the right hand side.

If you look at the final GMFM score, it continues the steady increase seen previously. Adding the percentile data shows how this child is faring in comparison with children of similar age and degree of disability. This data shows a plateauing where the child is not maintaining the same rate of change from measurement point 3 to 4 as in the previous measurements. This does not negate the improvement made by this child but is a reminder of the value of the percentile scores.

In a similar fashion consider these results from a child classified as GMFCS V where there appears to be a steady decline in performance.



Revealing the percentile results shows that their peers would be losing performance at a faster rate so this child is really doing well.

Now read on if you would like the app to help you produce your own similar results.


This Excel based calculator allows entry of measurements from up to 10 assessments of a child for whom the GFMCS classification has been selected.   Given the birth date and assessment date it will calculate the child’s age at each assessment.


N.B.  The app contains macros and your protection software will probably issue a warning about possible viruses.  We have checked the coding with a virus checker but you should only proceed if you trust us.

Excel will probably warn you that you need to enable macros by clicking on the yellow warning message.


When the App loads the opening screen appears.

If you are content with the words in the yellow box click on the green “Accept” button causing this new red button to appear:

The APP can be started by clicking on this button which ensures that all previous data is cleared.

The calculator needs to know the child’s date of birth and the GFMCS classification of the child and these are set up as shown below:

Entries should only be made in white boxes (any other entries will have unpredictable results).  The child’s date of birth (DoB) should be entered into the box that the red arrow points to (The two boxes above may be left empty or you can use you own reference and name entries as you prefer). Note that DoB must be in DD/MM/YY format and the child’s age must be between 2 and 12 years.

The appropriate GMFCS classification can be selected by using the 2 left and right buttons identified with the black arrow. The graph on the RH side will change as you click on these buttons which can be rather fun.

Now data from up to 10 assessments can be entered (please enter then in ascending date order:

For each assessment give the Assessment number 1, 2, 3, etc followed by the date (again in DD/MM/YY format) and then enter the GMFM-66 score in the lower box.  Once all boxes are correctly filled out you may click on the yellow O.K. button.  This causes the age and percentile value to be calculated and this information is displayed in the middle table and plotted on the graph.  As you add more assessment information the table and chart will develop.

Clicking the grey ‘RESET’ button clears all data and returns to the opening screen condition.

At any stage you can see the resulting graph by selecting the ‘REPORT’ tab at the bottom of the screen and this screen may be printed if a hard copy is required.

To help you comply with local data protection legislation we suggest that the app is never saved when it has been used with data.  Simply close the app using the red X at the top right.





Therapists and families of children with cerebral palsy or other problems of movement control often encounter the stage where their child seems to become less able and appear to ‘lose functional skills’. “My child used to be able to sit without support/stand/walk and now they can’t. What is going wrong?” This can be very distressing, especially for families, and can lead to feelings of guilt.

Look at this Discussion about growth and control. It helps to explain why a child who has problems of movement control can find functional abilities increasingly challenging as they grow older, taller and heavier.


Is there anything that can be done? 

You will see that, as a child grows, control abilities become more critical to maintaining levels of function and ability. A therapy programme that has a focus on improving control is important, especially when the child is young, so that control and function are maximised as young as possible. But don’t forget that the effects of growth will still occur. It cannot be stopped and it’s no-one’s fault. Children grow!

For now you might like to look at this short presentation exploring the relationships between Growth and control discussion


If you have found this free information useful please consider making a small donation to help keep this site going.