[How it works]

The XT9 High Activity Knee functions differently than any other knee.  It is the only AK prostheses that mimics the functions of the quadriceps in high activity sports.  The XT9's specialized "coil over air" shock system/control unit makes the XT9 the only 'energy storing' prosthetic knee on the market.  As pressure is applied to the limb, the knee bends, compressing over 400 pounds of energy in the coil spring and air shock.  This spring and shock tension, combined with hydraulic flexion control, act supportively as the quadriceps would in a sporting situation.  The knee is allowed to bend to about 90 degrees before coming to a rest against the titanium hard stops, at which point the energy that has been built up and stored in the spring system is ready to release, returning the athlete to a ready stance.
In activities such as snowboarding and other board sports, which have often been impossible for above knee amputees to enjoy with an artificial limb, the XT9 works naturally providing constant support and dynamic flexion and extension assist as the rider turns, absorbs bumps and rough terrain, and even performs jumps and tricks.
The heavy duty support which the XT9 knee offers an amputee is what allows so many high energy sports to now be enjoyed.  The XT9 High Activity Knee has adjustable stance which allows the user to set an active stance which suites his or her activity and level of ability.  Unlike other prosthetic knees, the XT9 is capable of supporting the user in an activity stance and works dynamically as a natural limb would do specifically in these kinds of activities.

[Pros and Cons to the XT9 Energy Storing Prosthetic Knee]

It is important to know that the XT9 Knee only works for the activities it does because we took a radical deviation from conventional prosthetic design in creating the first ever energy storing prosthetic knee.  This means that it functions very differently than other prosthetic knees.  These knees have been designed very effectively to function for walking, running and everyday activities.  The XT9 is not designed to function well for the same uses.