A variety of lower extremity injuries can occur as a result of decreased ankle mobility, specifically decreased dorsiflexion (see my posts on this HERE and HERE). The ankle dorsiflexion test is my favorite tool for assessing dorsiflexion mobility because it doesn’t require any tools or training, can be quickly performed, and has been shown to have excellent reliability (source).
To perform the test, have the athlete barefoot and kneeling with the tested leg in front. The 1st toe should be 3-5 inches away from the wall depending on their height. The athlete then shifts their knee forward, trying to touch the wall with the knee cap while keeping the heel flat on the floor. If the knee cap touches, you can be fairly certain that the athlete has sufficient dorsiflexion mobility. If they cannot touch, dorsiflexion is restricted.
It is important to note that the posterior leg can limit this as well if hip extension is very limited. In this case, have the patient/athlete perform the same test while standing with the tested ankle on a chair or stool.