Internal and external rotation of the knee is a popular test especially in ski-ing populations. The popliteus and hamstrings muscles play a significant role in rotating the knee (internally and externally) to aid unlocking and locking the knee.
It should be noted that this position stretches the ligaments at t the rear of the knee and can impinge the meniscus (cartilages) at the posterior horns.
This could be the effect you want some patient populations (like ski-ing) but in many cases can lead to injury.
Care should be exercised if using this test.
Until the late 1970s 75% of all isokinetic use and research was based on a single joint system - the knee. With more recent progress in rehabilitation and knee surgery this trend no longer exists. The basic design of isokinetic dynamometers (except for special purpose units) has not changed since the original instrumentation became available in the 1960s. The design is still better suited for knee testing and rehabilitation than any other joint (Dvir 1995). Although the knee has 2 major articulations the relevant one in this section is the tibio-femoral component.
Testing and exercise are generally performed in the sitting position although absolute hamstring testing is best performed in the prone lying position as this allows a greater range of motion and functional testing is best performed in the standing position. However, flexion and extension can be performed in either the Seated (most popular), Prone lying, Supine lying or standing positions.