It is the clinical experience of the authors that some children with cerebral palsy who walk in crouch gait show sufficient knee extension during the clinical gait analysis, but walk in considerable knee flexion when they leave the gait laboratory. Possible differences between walking in a gait lab and walking in daily life may be caused by the effect of observational awareness in the lab (also known as the Hawthorne effect), and the lack of dual-tasks (DT) during the analysis (which are common during daily life walking). Since so far there is no technique to reliably measure gait kinematics in children with CP outside of the laboratory, the researchers aim to objectify the influence of both the Hawthorne effect and dual-tasks by introducing different conditions during a standard clinical 3D gait analysis.

Study design: Observational study

Study population: Patients with cerebral palsy, bilateral spastic, knee flexion gait pattern, GMFCS classification I-III, age 4-16 years.

Objective: To determine the effect of observational awareness (the Hawthorne effect) and dual-tasks on spatiotemporal and kinematic variables during a clinical 3D gait analysis.

Primary research question:

Does reduced observational awareness and/or introduction of a dual-task influence knee flexion in stance phase in children with spastic diplegie cerebral palsy and knee flexion gait?

Secondary research questions:

1. Does reduced observational awareness and/or introduction of a dual-task increase toe walking in children with spastic diplegie cerebral palsy and knee flexion gait?
2. In children with spastic diplegic cerebral palsy and knee flexion gait, do spatiotemporal gait parameters change when observational awareness is reduced and/or a dual-task is introduced?

Conditions in which gait data will be gathered:

1. With awareness of observation + without Dual-task
2. With awareness of observation + with Dual-task
3. Without awareness of observation + without Dual-task
4. Without awareness of observation + with Dual-task

Inclusion Criteria:

• Cerebral palsy, bilateral spastic, GMFCS classification I-III
• Age <16 years
• Use of bilateral AFO's (rigid or ground reaction AFO's) to improve knee extension in stance

Exclusion Criteria:

• Behavioural issues or poor instructability which might affect participation in the protocol
• Significant visual disorders
• Other diagnoses influencing gait
• Not willing to sign informed consent before inclusion

All subjects are recruited from the patient base of Roessingh Center for Rehabilitation. Subjects will be included in the study when a clinical 3D gait analysis is due and the inclusion and exclusion criteria as mentioned are met.