Squats are king . . . This phrase has echoed through fitness communities as long as I can remember. Some experts have even stated that squats are the only lower body exercise you will need. Don't get me wrong . . . I love squats and the whole body workout benefit it provides. Destroy your quads, your hamstrings, and core all in one motion. Who wouldn't love that. But here is some interesting information that has come about.
Some studies have shown unilateral exercises can actually activate your outer quads more effectively. This happens based on the necessary balance and stability requirements of the motion. At the end of the day, if you are looking to increase muscle size in a specific muscle group . . . Performing just one exercise isn't going to cut it. Every muscle unique neuromuscular sections that are activated differently and by variation in exercises.
So, not saying to give up on squats . . . Keep those going strong . . . But, get more quad activation by incorporating Lunges and Step-Ups.
Check out the chart below for outer quad activation by exercise: