Project Knee-Mo:
Aquatic Pediatric Knee Immobilizer
Designed an aquatic pediatric knee immobilizer to help a physical therapist perform aquatic therapy with children with cerebral palsy
Product Manager
Lead Designer & Prototyper
Materials selection
Shirley Ryan AbilityLab
Chicago, IL
Dsgn 106-1
Design Thinking and Communication
‣ Our client needed an aquatic knee immobilizer that is durable and safe for children with cerebral palsy to be used during pool exercise sessions
• Client needs help performing pool exercises with children affected by cerebral palsy, a condition
that causes poor coordination, stiff and weak muscles, and tremors
• Client needs legs to be safely and comfortably immobilized and kept straight while she can focus
on upper body exercises
• Previous student-made aquatic pediatric knee immobilizers broke quickly, none exist on market
• Cerebral palsy is a neurological disorder caused by brain damage before, during or immediately
after birth.
• Muscles can tighten and spasm – stretching and exercise can relieve the tightness and facilitate
blood flow
• Fertilizer solution is made at the farm and filtered to water-like consistency
• Ideally, our solution should be attached to the tractor and seedbox plow
• Aquatic therapy is very effective method of rehabilitation that can be less painful and straining
than land-based therapy
• It is a great form of stretching and exercise for rehab patients with cerebral palsy
• It is difficult for one physical therapist to assist their patients with certain exercises in the water
while holding other limbs in place
• Immobilizer will be put on in the water - it should be a fast and easy one-person process
• Pool water has more chemicals than regular pools - we took samples for later testing
Pool where aquatic therapy takes place
‣ Conducted a brainstorming session with students in our class to expand our creativity and develop new ideas
During our brainstorming session, I thought back to my experience with scuba diving. It is a sport that requires durable and waterproof materials that are critical to a safe and successful dive. I also thought about the attachment mechanisms of the buoyancy control device (BCD) on which divers' lives are dependent. Divers put on a BCD like a life jacket. It first has velcro to secure the it around the diver's upper body. After the velcro is secured, the buckles are attached and tightened. This double attachment method causes the tension of the tightly secured BCD to distribute across multiple parts and materials, reducing wear and tear. I explained these aspects about the BCD to my class and noted that we should look into what materials divers use that we could also use to construct our knee immobilizer.
We also thought about what materials could we use to keep the immobilizer straight. After researching knee immobilizers on the market, we learned that rods are used to keep the immobilizer stiff on the leg. We decided to adopt this approach and use rods as well.
I found a scuba diving shop in a nearby town and rented a BCD to show members of my team and our client how it works. Our client was initially opposed to using velcro, because it wears easily. After seeing the double attachment mechanism for the BCD, she understood that velcro could work given the force distribution. She urged us to use the same wide width of the velcro of the BCD.
Bouyancy control device (BCD) with velcro and buckle fastening system
We cut a PVC rod with dimensions according to the average leg length of our client's patients. We showed her the rod and that one would be attached on both sides of the leg. She liked the positioning of the rods, but noted that the rods should be bent at an angle so that it could accomodate the natural bend of a straight leg.
14inch PVC rod
‣ We used materials commonly found in scuba gear
We researched common materials used for BCDs and scuba gear. We wanted the knee immobilizer to be comfortable and durable. To do this, we decided to have two layers of material in our prototype. The inner layer, which is in direct contact with the user's skin, is made of neoprene, a waterproof synthetic rubber commonly used in wetsuits. It is soft, comfortable, and will protect the skin from the rods of the knee immobilizerer. The inner layer also includes the soft part of velcro.
Inner layer of Knee-Mo featuring neoprene and soft velcro
The outer layer of Knee-Mo was made out of waterproof 500 Denier Cordura nylon fabric, which is used in BCDs. It is very dense and durable, making it suitable to withstand the tension of the rods and fastening system.
We decided to use PVC to make the rods, because it is durable and waterproof. We sewed it in place under the nylon fabric. We hand stitched and used a sewing machine to stich the layers and buckles together.
Outer layer of Knee-Mo featuring nylon fabric
‣ A waterproof knee immobilizer made for children that fastens similarly to a bouyancy control device
Application
Knee-Mo is first wrapped around the leg and secured with velcro
It is then tightened in place with buckles
