ERMI is the abbreviation of End Range Motion Improvement - a rehabilitation device to improve end range of motion of the knee.
Why is 'end range of motion' important?
One can get away with a lack of quite a few degrees of flexion, but extension (straightening) is much more imporant to acheive. The lack of only 5 degrees or so of extension means that one cannot lock the leg back while standing, and this causes stress on the whole frame.
Torque Measures of Common Therapies for the Treatment of Loss of Knee Flexion. Uhl TL and Jacobs CA. Sports Health. 2012 Mar; 4(2): 101–106.