Orthopaedic instrument for balancing the knee during TKR-surgery

During Total Knee Replacement-surgery it's of high importance to properly balance the collateral ligaments of the knee. For BIOMET we developed a product that can standardize and improve this procedure.

Analysis of the TKR-procedure and balancing the knee

Through observing the procedure and a series of interviews with orthopaedics we gained detailed knowledge of the why, when and how of this balancing.

It appeared this is now mostly done based on the surgeon's feeling and sight. On one hand this can be good as the orthopaedic is in total control, on the other it makes his balancing impossible to quantify, replicate and standardize and therefore improve.

Several products do exist can measure the balance inside the knee but are purely mechanical. The internal placement can furthermore hinder the operation and are not often used.

We decided to go a different direction and looked for and found a way of measuring the balance from outside the knee: by comparing deflection of the lower leg in set forces exerted by the orthopaedic to both sides.

Looking for ways to measure the balance in the knee, from outside the knee

Ideation of a smart brace and interface

At least 2 elements were needed to be developed for main elements: a smart brace with force sensors (measuring the exerted forces by the orthopaedic surgeon) and a 9-DOF sensor (measuring deflection of the lower leg) and an interface to visualise the balancing.

We prototyped and tested an array of different brace designs with different ways of measuring the orthopaedic's force. The final brace-design resembles a regular ankle brace, fitting properly around the ankle through padding and adjustable straps and for the surgeon to easily grab the ankle like he/she is used to without the use of this design.

The interface needed to be both accurate and somehow intuitive as the surgeon will sometimes have only short intervls to check the screen. We provided in this by showing both graphical, colored bars and numerical output.

Iterative sketches of possible brace-designs

Interface and KeyShot render of the "KneeBalance"

Prototyping & testing

We presented and tested the concept and prototype (installed on a simulation leg) at a orthopaedic conference. Orthopaedic surgeons saw its value and found the interface and interaction easy to understand. Physiotherapists furthermore, saw another usecase for their own practice as the knee does not need to be opened up to measure balance.

Physical prototype of the ankle brace,

Testing the prototype at a conference for orthopaedic surgeons


My focus in this project was firstly on analyzing the procedure and balancing, creating and illustrating the user flow of the product and ideation and prototyping of the different options for the brace and prototyping its final design.

What I especially enjoyed within this project was the innovativity and the great atmosphere and drive within the group. Each member had its own specialities and knowledge leading to many meaningfull discussions, ideation & brainstorm sessions.

Time & Team

4 months

4 days a week

Team of 6 IPD designers