A simple way to periodize your training is by constantly varying your movements for a specific muscle group. Squats are great for building your legs, but they’re not the end-all, be-all. Add variations to your training to maximize gains and to keep training interesting!
Reference: Fonseca, R. M., Roschel, H., Tricoli, V., de Souza, E. O., Wilson, J. M., Laurentino, G. C., … & Ugrinowitsch, C. (2014). Changes in exercises are more effective than in loading schemes to improve muscle strength. The Journal of Strength & Conditioning Research, 28(11), 3085-3092.