Lower Extremity 

Iliopsoas

The iliopsoas muscle is actually two muscles: iliacus and psoas major. Most people refer to this muscle as their ‘hip flexor’. If you were a pig, we’d call this your “tenderloin”. They have different origins but come together to attach on the lesser trochanter of the femur.

Gluteus Maximus 

The gluteus maximus is one of the largest and strongest muscles in the body. This muscle is a good example of being named for its location and size. This is also a common site for intramuscular (IM) injections, especially for larger volumes that dissipate over a longer period (such as penicillin or gamma globulin).

Gluteus Medius 

The gluteus medius is an important muscle for hip and knee stability and control. It is located on the lateral hip. Much like the deltoid, it is a common location for injections.

Sartorius

The sartorius is the longest muscle in the body.

Muscle Compartments

In studying the muscles of the thigh, it is helpful to know that the thigh is divided into three compartments. Blood vessels and nerves run in “seams” between the compartments.

1. Medial compartment contains adductors (purple in image)
2. Anterior compartment contains quadriceps (blue in image)
3. Posterior compartment contains hamstrings (green in image)

Other limbs, such as the lower leg, have similar compartments but we will not study them in this course.

Hip Adductor Group 

The adductors are comprised of the muscles in your medial thigh. They are housed in the medial compartment. Much like the wrist flexors and extensors, we are grouping the hip adductors together. These are typically referred to as your “groin muscles”.

Quadriceps Group

The quadriceps muscle group is comprised of the anterior thigh muscles. These muscles are housed in the anterior compartment of your thigh.

Hamstring Group 

The hamstring muscle group is comprised of the posterior thigh muscles. These muscles are housed in the posterior compartment of your thigh. They have unique names, which are explained in the table below.

Gastrocnemius

The gastrocnemius is the muscle that is often referred to when talking about the “calf muscles”.

Soleus

The soleus is deep to the gastrocnemius. Much like the brachialis, the soleus does not get much credit for the work it does because you do not see much of it from the surface of the body.

Tibialis Anterior 

The tibialis anterior is the muscle on the anterior leg (crus). This muscle performs dorsiflexion which is important for walking so you don’t trip over your feet. This muscle is often impaired as part of a stroke and patients develop drop foot.

Tibialis Posterior 

The tibialis posterior is the shin-splints muscle. It helps support your arch and when you run or jump a lot, it can get overworked and painful.

Fibularis/Peroneal Group 

The fibularis muscle group consists of three muscles. These muscles are also called the peroneal group. You can use the names interchangeably. Here,we will use fibularis to name the muscles based on their anatomic location. These muscles work together to prevent your ankle from rolling inward (inversion), the most common type of ankle sprain.