You may not understand exactly what causes a tight IT (iliotibial) band, but you've probably experienced that uncomfortable tension along the outside of your thigh. While it's not actually a muscle, the IT band may require daily stretching, says Suzanne Semanson, physical therapist at New York University Langone Medical Center's Harkness Center for Dance Injuries. The IT band is made of fascia, or tough connective tissue, that attaches to the pelvis through the tensor fascia lata (or TFL)—a small muscle between the pelvis and femur—and runs down to the outside of the knee.

When you're dancing with a fully extended knee, the IT band stabilizes the knee so that it doesn't move sideways out of alignment. However, “it is commonly tight in dancers due to compensatory patterns and overuse of the TFL," says Semanson. For example, if you force your turnout too much from your knees or rely on the TFL (instead of muscles in the hip) for développés to the front or side, this area might be too tight. The IT band and TFL can also build up excess tension from the demands of dancing several hours a day.