When you perform the 1st CMC grind test, compress the joint and rotate thumb metacarpal. It’s the same motion you would use when using a mortar and pestle (Licensed from Shutterstock). Source: The Hand, Wrist, and Elbow, Practical Office Orthopedics Citation: Parks E. Practical Office Orthopedics; 2017 Available at: https://accessmedicine.mhmedical.com/DownloadImage.aspx?image=/data/books/2230/parksortho_ch4_f021-4-b.png&sec=172778630&BookID=2230&ChapterSecID=172778553&imagename= Accessed: January 03, 2018 Copyright © 2018 McGraw-Hill Education. All rights reserved