While it may sound like an astrological star sign, the sartorius actually the longest muscle in your body, stretching from the anterior superior iliac spine (ASIS) to the medial knee. Named from the Latin sartor ‘tailor’, (commonly thought to have attained this name in reference to the activation of the muscle when sitting in the cross-legged position once adopted by tailors). It also is a bi-articular muscle, meaning it operates on two joints, the hip and the knee.
Like Cinderella, the sartorius is often overshadowed by its more famous “step-sisters” − the psoas and iliacus − as a cause of anterior hip pain. Yet an overly tight sartorius can cause acute discomfort at the front of the pelvis. Like the iliopsoas, it can also adaptively shorten due to sitting, which results in chronic dysfunction. This dysfunction can have concomitant far-reaching effects throughout the body. For example, considering the downward pull of the sartorius on the ASIS, chronic tightness in this muscle has the potential to cause stress and impingement in the lumbar spine.
At the hip, the sartorius acts in synergy with the iliopsoas for hip flexion and aids the lateral rotators (gluteus maximus, obturators internus and externus, gemelli superior and inferior, quadratus femoris and piriformis) to create hip external rotation. Along with the tensor fascia latae, gluteus maximus and gluteus medius, sartorius abducts the hip. At the tibiofemoral joint, the sartorius is a synergist in knee flexion (working with the prime movers – biceps femoris, semitendinosus, and semimembranosus) and involved in medial rotation of the flexed knee. The next time you look at the sole of your shoe to see if you have stepped in gum, give a shout out to your sartorius (and it’s back up band), which is orchestrating all these directions of movement simultaneously!
Because it crosses at the knee, the sartorius can also be a cause of medial knee pain. Joining with the tendons of gracilis and semitendinosus to form the pes anserinus (PA) tendon, tightnessdysfunctional movement patterns and over use of any of these muscles can result in inflammation at the PA tendon, and sometimes its under-lying bursae. This inflammation may be experienced as pain or hypersensitivity on the inside of the knee.
Other symptoms of sartorius-related muscle pain can include a burning or stinging sensation at the front of the hip. This pain may be brought on by an overt trauma, such as an athletic injury. Sports which require sharp turns around a planted foot, such as basketball and football, or a fall whilst skiing where one foot remains trapped in deep snow, can expose the sartorius to unexpected and sudden torsional forces resulting in muscle strain and tissue damage.
Outside of acute injury, however, poor postural and alignment habits can also contribute to sartorius-related pain. Now that you’ve read this introduction to sartorius anatomy, check back in on Friday to read more on how our habits may be contributing to sartorius dysfunction and how Yoga Tune Up® can provide relief!
 Rennie, W.J. & Saifuddin, A. Pes Anserine Bursitis: incidence in symptomatic knees & clinical presentation. Skeletal Radiol (2005) 34:395-398