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Wearable ACL Tear Detector

Did you know that the knee is the largest joint in the body, and one of the most easily injured?

Among Indians, one of the most common injuries is Anterior Cruciate Ligament tear that affects the knee. ACL is also responsible for providing almost 90% of the stability to the knee joint.

Our goal was to create a device that could accurately measure the pressure being applied to the knee. The perfect device would be user friendly and provide the right information to the user, so that he/she could take the appropriate remedial action and avoid further damage to the knee.

Before the prototyping started, we tried to understand the basic working of the knee. So the knee is a joint that is formed by three bones: Femur (the long bone extending down from the hip); Tibia (the bone between the knee and ankle); and Patella (the kneecap). These bones are joined together by a number of ligaments. Two ligaments crisscross in the joint from the femur to the tibia and are called cruciate ligaments (cruciate means cross). The one towards the front of the leg is called the Anterior Cruciate Ligament.

In 2015, Lionel Messi had a Medial Collateral Ligament tear and needed 2 months to recover.


It was mostly prevalent in sports like skiing, athletics, basketball, soccerwhich includes lots of stop-and-go movements, jumping, or weaving. The fact was that 60–80% of ACL tears occur without contact with another athlete. This could happen when you are changing direction rapidly, slowing down when running, and changing speed while running or landing from a jump. We also found that according to the American Academy of Orthopedic Surgeons, ACL injuries are two to ten times more likely to occur in female athletes than in male athletes.

Famous athletes who have had ACL tears included Yuvraj Singh and Tiger Woods. We also got to know that ACL tears often occurs in sports but is seen commonly in people who are maintain a highly active lifestyle. Those above the age of 40, who walk and jog just to keep healthy are also equally prone to ACL.

The major disadvantage with ACL tears and similar ligament injuries was that they showed up in an aggravated stage after many months or years. Once you have diagnosed an ACL injury, it could take six to nine months to return to normal activity.

The global self care medical device market will be valued at $16.9 billion globally in 2019. This includes the sale of Blood Glucose Monitors, Pedometers, Sleep Apnea Monitors and Nebulizers. As technology has advanced, more people are demanding to receive at-home care, and the demand for self-medication is increasing. Conditions that require lifelong monitoring will definitely require self-care devices that can be easily adopted to save time and money.

Every year, more than 50,000 people in India undergo ACL surgery. Also we knew that ACL surgery is expensive and cannot be afforded by a large population in India. The actual population suffering from various degrees of ACL tears in India is close to 10,00,000.

Technology could also come to the the rescue of animals. Dogs, cats and horses are prone to injuries similar to ACL tears. By preventing these injuries with early diagnosis, surgery can be avoided saving between $2000 to $5000 per incident.


Two bright minds came together to solve this problem, in the form of Shiva Sharma and Tadichetty Nihar. They were also assisted by Dr. Vipin who helped them in the process of goal-setting and execution.

The Idea was creating a wearable device that detects the amount of force acting upon our knee, depending upon the force that acts and the comparison between the obtained values and the ranges of standard thresholds of an ACL it can give the probable grade of tear caused.

The device consisted of piezoelectric sensors which are fabricated accordingly to avoid any damage to the sensors and to pick up the vibrations effectively. An array of sensors was used for effective detection. The piezoelectric sensors were calibrated by applying known amount of force on it and by measuring the corresponding voltage drops across the piezoelectric.

The prototype was made by integrating the entire circuit onto a knee cap. The device is currently powered by a universal Serial Bus cable (USB). The entire circuit has a potential to be reduced into a Printed Circuit Board (PCB) and can be powered by a button cell to make it more wearable.


“Technology, like art, is a soaring exercise of the human imagination.” — Daniel Bell

The ideal situation would be where the ACL tear can be detected at an early stage. This is the goal that many designers, developers and doctors around the world are working towards.

But as of now we have been able to detect the pressure that is being applied on the knee. This device can be improved to a great extent. In the future it can become a device that can worn throughout the day. It could be connected to a mobile device and show the information as a notification as when a particular threshold is crossed. This will ensure that a damaged knee has the proper care while participating in strenuous physical events and especially while recovering.

The issue is that many people have trouble with their knee and keep ignoring until it becomes unbearable. Their gait or walking style is altered when they have a niggle in the knee but they keep walking in that manner for a long time. This leads to the condition becoming worse. This device will also need to analyze the moving of the limbs and suggest corrections. It must become a one stop self care device to measure knee problems in the early stage and suggesting solutions.

To share your ideas and participate, check our Initiatives page.

Originally Published on April 05, 2016

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