WiSys Technologies

Easy-to-Use Device to Measure Range of Motion in Knee During Post-Operation Recovery

WiSys is seeking a strategic partner for further development, validation, manufacture, sales, and distribution of a new range of motion measuring device that will lower physical therapy costs and improve comfort for patients recovering from hinge joint operations or for patients with movement disorders.

WiSys Technology Number: T160048
Patent Filed: April 26, 2017
Stage of Development:

A prototype has been developed for this technology and has undergone preliminary studies to validate functionality and accuracy. Further testing will be needed to verify consistent usability by patients, as well as to gather more data on their needs. The estimated cost of production of the current version of the device is $50, and additional development would be needed to optimize the design for mass-manufacture and ultimately decrease the production cost. Further software development may be needed to produce data output for various potential end-users, including patients and physical therapists.


In the United States, approximately 5.2 million knee replacement surgeries were performed in the 11 years between 2000 and 2010, and U.S. hospital costs from total knee replacement were estimated at $41.7 billion in 2014. The number of these procedures in the U.S. is anticipated to be over 3.4 million in 2030 alone.

One standard indicator of progress in post-operation recovery is range of motion of the knee joint, which is typically measured by a physical therapist using a handheld, protractor-like device called a goniometer. Although simple, a goniometer can be easily misaligned, causing up to 5 degrees of measurement error. In addition, it requires a second individual besides the patient to make a reading while the knee is stationary. This need for another person increases numbers of visits to the physical therapist and therefore increases cost. The patient can also experience discomfort or pain while having to hold the joint still for measurement.


Inventors at University of Wisconsin-Platteville have developed a novel device that enables an individual to reliably measure range of motion of his or her own knee joint while avoiding the discomfort of holding it stationary. The core function of the device relies on commercially available sensors containing a flexible electroactive polymer that measures movement and stretching. The battery-powered device aligns to the knee using braces secured by Velcro straps to the patient’s thigh and lower leg, and the sensors are connected to these braces. As the lower leg moves relative to the thigh, digital measurements are transmitted by wireless signal to a handheld device such as a smartphone or tablet and can be read instantaneously by the patient or shared remotely with a doctor or physical therapist. The device can measure angles as the knee moves and does not require the joint to be held still for an extended time.

Preliminary studies indicate that measurements taken by a prototype of this range of motion device are at least as accurate as a standard goniometer. These results support this new device as a powerful new tool that can enhance patient comfort and reduce the cost of post-operation care. Future development could adapt this technology for use on other hinged joints such as elbows.


  • Measures range of motion of the knee; May be adapted for other hinge joints such as the elbow
  • Use in post-operation physical therapy following total knee replacement
  • Monitors mobility of joints in patients with movement disorders such as cerebral palsy
  • Device can be used by individual to measure own joint movement, rather than needing physical therapist to read
  • Measurements can be taken while joint is in motion rather than held stationary
  • Digital measurements recorded and reported by app on handheld device 


  • Lowers cost of physical therapy by decreasing number of visits to or from the physical therapist
  • Enhances patient comfort
  • Fast measurements
  • Easy record-keeping
UW-Platteville UW-Platteville
Jacob Knabe
Joshua Inglett
Kyle Valenza