Tight Hip Flexors
Your hip flexors, otherwise known as your illiopsoas actually consists of two muscles. The Iliacus and the Psoas Major. The Iliacus originates on your pelvic crest and attaches on the top of the femur, which is the big bone on the top of your leg. The Psoas Major, is thelonger of the two muscles and it starts at the lumbar vertebrae and attaches to the femur as well. There is also another muscle that can contribute to hip flexion. The Rectus Femoris. This is actually one of the quadriceps muscles, however because it attaches to the hip joint and below the knee, crossing two joints it performs hip flexion and knee extension.
Many people get tight hip flexors, for various reasons. These can often cause low back pain, as the pelvis is tilted forward constantly. We will go into this a little more later.

