Gross Motor Function Measure (GMFM-66 & GMFM-88): Protocol & GMFCS Tracking
In short
The Gross Motor Function Measure (GMFM) evaluates gross motor capacity changes in children with cerebral palsy. Learn the difference between GMFM-88 and GMFM-66.
In this guide (4 sections)
What Is the Gross Motor Function Measure (GMFM)?
Developed by Dianne Russell and the CanChild Centre for Childhood Disability Research in 1989, the Gross Motor Function Measure (GMFM) is the premier evaluative instrument designed to quantify motor capacity in children with cerebral palsy and Down syndrome.
Unlike norm-referenced developmental motor scales that compare a child against typically developing peers, the GMFM evaluates what a child can do independently regardless of atypical movement patterns.
GMFM-88 vs GMFM-66: Key Differences
The original GMFM-88 contains 88 items across 5 gross motor dimensions scored on a 4-point ordinal scale from 0 (does not initiate) to 3 (completes item).
The updated GMFM-66 uses Rasch analysis to create an interval-scaled measure of 66 selected items, eliminating items with poor item difficulty hierarchy. GMFM-66 requires the Gross Motor Ability Estimator (GMAE) software for conversion.
| Dimension | GMFM-88 Items | GMFM-66 Items | Core Developmental Motor Skills Tested | |
|---|---|---|---|---|
| Dimension A: Lying and Rolling | 17 items | 4 items | Head turning, supine to prone rolling, reaching across midline, lifting head. | |
| Dimension B: Sitting | 20 items | 15 items | Supported and unsupported sitting, reaching, ring sitting, pivoting, floor transfers. | |
| Dimension C: Crawling and Kneeling | 14 items | 10 items | Prone crawling, quadruped creeping, high kneeling, half kneeling, transitions. | |
| Dimension D: Standing | 13 items | 13 items | Pulling to stand, standing with/without support, single limb balance, floor to stand. | |
| Dimension E: Walking, Running & Jumping | 24 items | 24 items | Cruising, supported walking, independent walking, running, stair climbing, hopping. |
Integration with GMFCS Levels and Motor Growth Curves
GMFM scores are interpreted alongside the Gross Motor Function Classification System (GMFCS Levels I to V).
Motor growth curves established by Rosenbaum et al. demonstrate that children with cerebral palsy reach their gross motor peak at approximately 5 to 7 years of age. GMFM tracking confirms whether a child is tracking along their expected developmental trajectory or plateauing.
- GMFCS Level I: Expected GMFM-66 peak average is 85 to 90 points.
- GMFCS Level II: Expected GMFM-66 peak average is 65 to 70 points.
- GMFCS Level III: Expected GMFM-66 peak average is 50 to 55 points (uses manual wheelchair for long distances).
- GMFCS Level IV: Expected GMFM-66 peak average is 35 to 40 points.
- GMFCS Level V: Expected GMFM-66 peak average is 15 to 20 points (dependent in all mobility).
Frequently Asked Questions
Can a child wear ankle-foot orthoses (AFOs) during the GMFM?
Yes. The GMFM can be tested without shoes and orthoses, or with footwear and orthoses. The testing conditions must be clearly documented to evaluate the functional advantage provided by the brace.
When should GMFM-88 be chosen instead of GMFM-66?
Use GMFM-88 for children with severe impairment (GMFCS IV and V), children with Down syndrome, or when evaluating use of assistive devices like canes or crutches.
What is the Minimal Clinically Important Difference (MCID) for GMFM?
A change of 1.1 to 1.3 points on the GMFM-66 represents a clinically meaningful difference in gross motor capability.
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