The purpose of the study is to examine the outcomes of home-based robot-guided therapy and compare it to laboratory-based robot-guided therapy for impaired ankles in cerebral palsy. Children with spastic cerebral palsy (CP) are randomly placed into two groups, participating in robot-guided stretching and active movement training either in a research lab setting (Lab group) or in a home setting (Home group).

Children with spastic CP will be randomly placed to 2 groups, either a Lab group or a Home group. For both groups, the participation will involve 18 training sessions over 6 weeks with 3 sessions each week. Each training session will last about 45 minutes, including stretching and active movement training.

The participant will be asked to sit with the foot secured to a footplate and leg fixed by a leg-support. Once the rehab robot is on the child's ankle, the investigator will first determine maximum range of motion that is safe for the ankle stretching. The robot will then move the ankle joint slowly within the set range of motion, and stretch the ankle back and forth. The passive stretching will help loosen the child's muscle and increase range of motion in the ankle joint. Passive stretching will last about 15 minutes.

After stretching, the investigator will ask the child to move and control the ankle joint back and forth to complete video-game tasks. While the child moves the ankle, the robot will provide assistance or resistance to improve control of the ankle joint. Active movement training will last about 20 minutes.

For Home group, the family members will be trained by the research team at the lab on how they use the rehab robot properly. On the day of the first assessment, the investigator will go through the device operation with family members. A detailed user manual will be given. The investigator will allow the family members and the child to practice using the device as many times as needed until the participant feel comfortable using the device at home. The family members should prepare for a minimum of one hour for this instructional period to learn the device, but they will be allowed as much time as needed.

Before leaving UMB to begin at-home training, the family members will be checked for the competency of using the device. The family members will be asked to go through each step without any direct assistance with the research staff. The family members may use their own vehicle to take the portable rehab robot home. While the family members are doing training for the child at home, the training data will be saved automatically in the laptop with the rehab robot.

Only one ankle joint will be allowed to treat using this robotic device. The investigator will choose the more impaired side ankle of the child to start the training. The investigator will follow up with the family members 1-3 times per week to check in regarding the child's participation and any issues during the training. The family members can also call the research staff if they have any questions about the training. The family members should follow the same training plan during 18 training sessions unless the investigator decide to adjust the training setups based on the child's progress.

Outcome assessments

During the study, the child will have 3 assessment visits in the research lab. The visits will occur before and after 6-week training, and at a follow-up 6 weeks after the training ends. During the assessment, the child's ankle will be moved by the robot to test passive range of motion and joint stiffness. The participant will also move the ankle himself and the active range of motion and muscle strength will be recorded. Clinical exam scales will be done including modified Ashworth scale, Selective Control Assessment of Lower Extremity (SCALE), balance, and walking ability (distance covered in 6 minutes).

Inclusion Criteria:

1. Spastic cerebral palsy with diplegia or hemiplegia (affected both legs or one leg)
2. 6-17 years old
3. Can follow instructions and express any discomfort during the sessions.

Exclusion Criteria:

1. Orthopedic surgery, serial casting, or injection of muscle relaxants such as botulinum toxin type A within 6 months prior to participation in the study
2. Severe ankle contracture, greater than 20° plantar flexion
3. Other unrelated neurological impairments or musculoskeletal injuries
4. Can not sit for 1 hour