This works the glutes and TFL!
The gluteus medius is a thick muscle that is largely covered by the gluteus maximus. It works to abduct and medially rotate the thigh -- turning the thigh inward so that the knee points toward your other leg -- while also steadying the pelvis. When performing the side leg raise with your right leg, the gluteus medius on the right side is actively working to abduct the thigh while the gluteus medius on the left side is stabilising the pelvis.
The gluteus minimus is the smallest of the gluteal muscles and lies deep beneath the other two. This muscles aids the gluteus medius in pelvic stabilization and thigh abduction.
The tensor fasciae latae is a muscle enclosed between layers of connective tissue. The muscle itself is rather short and originates in the hips but attaches to the knee via the long, thick iliotibial tract. This muscle helps the gluteus medius and minimus muscles in thigh abduction and medial rotation. Because it crosses the knee, it also works to steady the joint, keeping it straight during the exercise.
