Range of motion (ROM) of the knee is the range in degrees through which the knee can bend and straighten (flex and extend).
Knee range of motion is usually measured with a simple plastic device called a 'goniometer', although more sophisticated electronic devices are available.
Normal ROM is usually minus 5 to 143 degrees in women and minus 6 to 140 degrees in men.
A plastic goniometer with longer arms is usually used to measure range of motion.
|The scale part of the goniometer is placed on the joint line.|
Increasing Knee Range of Motion Using a Unique Sustained Method. Shah N. N Am J Sports Phys Ther. 2008 May; 3(2): 110–113.
Smartphone-based accelerometry is a valid tool for measuring dynamic changes in knee extension range of motion. Støve MP, Palsson TS, Hirata RP. Knee. 2018 Jan;25(1):66-72.