Reliability of the gross motor function measure in cerebral palsy.

The Gross Motor Function Measure (GMFM), an instrument comprising five dimensions devised by Russell and co-workers (7) to measure gross motor function in children with cerebral palsy (CP) or brain damage, enables changes in performance status to be evaluated after therapy or when monitored over time. We analysed its inter-rater and intra-rater reliability on the three most difficult dimensions. A video-recording of three children with CP performing test tasks was assessed on two occasions at an interval of six months by each of the 15 physiotherapists using the GMFM manual but without previous experience or training in the use of the instrument. Mean percentage scores were similar at the first and second assessments. Both inter- and intra-rater reliabilities were good, inter-rater reliability being 0.77 and 0.88 at the first and second assessments, respectively, and intra-rater reliability 0.68 at the second assessment. The findings suggest the GMFM to be a useful and reliable instrument for assessing motor function and treatment outcome in CP.