IRQ in long sitting ("Short arc quads" Knee terminal extension strengthening, roller under knee, supine)

Lie on your back with a foam roller or rolled towel under your knees and let your legs hang over in a comfortable position.
Straighten your affected knee by tensing the thigh muscles, so that your heel comes off the table and the knee straightens.
Hold this position, then control the movement back down to the start position and repeat.