Hip flexor muscle size in ballet dancers compared to athletes, and relationship to hip pain.

•Iliopsoas, tensor fascia latae and sartorius muscle size was larger in ballet dancers compared to athletes.•Rectus femoris muscle size was similar in dancers and athletes.•Iliopsoas muscle size was smaller in participants with hip pain.•Tensor fascia latae, sartorius and rectus femoris muscle size was not related to hip pain.