Muscle Stretching Exercises for the Knees & Thighs. Part of the series: Yoga, Stretching & Muscle Health. Since your quadricep muscles insert into your patella tendon, you'll have to stretch your four quadricep muscles to stretch your knee. Find out about muscle stretching exercises for the knees and the thighs with help from an expert who was a competitive gymnast for seven years in this free video clip.