It’s important to understand the leg anatomy in order to understand how to optimally train the lower body…
I’ll give you a little hint before you continue on: the leg muscles are not as simple as just the quadriceps and hamstrings.
Specifically, this page discusses all the major muscle groups of the upper leg. In other words, this page excludes information about the calf muscles…
…You can read about the calf muscle anatomy here, if you are interested.
The leg anatomy is so complex, containing both the knee and hip joints. The hip joint allows you to move and rotate your legs pelvic area in all directions. The knee joint enables the movement of bending and straightening your legs.
It’s important to understand that greater range of motion and rotational freedom naturally lead to a higher chance of injury through increased use. This is why the old folks home is chock full of old people with metal hips and knees!…
…Which alludes to one major reason why you should understand the leg anatomy: to prevent injury. Of course the other reason is to build muscular legs that you could move mountains with – A little more short-term and narcissistic, but a great reason nonetheless.
That said, lets get on to the first step by understanding all the different movements made possible by the mechanics of the leg muscles and their respective joints…
Functions of the Leg Muscles
There are several muscle groups in the upper leg anatomy, each of which contains multiple individual muscles.
The muscle groups can work independently for specific movements. However, many of the leg muscles share functions with other leg muscles. And so they work together to carry out larger, more “natural” movements; this is why there is much overlap in terms of muscle groups worked, between the different compound leg exercises.
List of All Leg Muscles’ Functions. The following list contains a description of all of the possible functions of the muscles in the leg anatomy. I’ll try to explain each movement by describing it in more universal terms instead of simply listing an exercise, which may be ambiguous or altogether unfamiliar to some.
- Hip Abduction. With a straight hip joint, moving your leg away from the center-line of your body, outward and upward. If you’ve watched any Kung-Fu/Action/Fighting movies, then you’ve surely seen hip abduction performed to the extreme with gravity defying mid-air split kicks (sorry, that was the best example I could think of!).
- Hip Adduction. Moving your leg toward the center-line of your body. A practical way to demonstrate hip adduction is by clenching your legs together as if you’re crushing something (an opponent’s head maybe?) between your inner thigs.
- Hip Extension. The movement of straightening the hip joint to increase the angle between your thighs and torso. One way to do this is by moving your leg backward, as exemplified by a “donkey kick” motion (donkey kick also an exercise name); or move your pelvis forward, as demonstrated by the classic pelvic thrust (the “booyah!” and fist pump are optional).
- Hip Flexion. The movement of bending the hip joint to decrease the angle between your thighs and torso. This is exemplified by the knee-to-chest “tucking” movement performed by divers or gymnasts while flipping; or the chest-to-knee movement, which is done by performing sit-ups or similar movements.
- Internal & External Hip Rotation. Rotating your upper leg and pelvis to the inside or outside of your body’s center line. Try this movement out by standing on one foot with the other leg slightly raised. Then “turn over” the raised leg to the inside (internal rotation) or to the outside (external rotation).
- Internal & External Knee Rotation. Rotating the lower leg to the inside or outside from a bent-leg position. Try it out by sitting in a chair and putting your heels on the floor. Then pivot on your lower leg by turning your feet so that your toes point toward your body’s center-line (internal rotation) or away from your body’s center line (external rotation).
- Knee Extension. Knee extension constitutes the movement from a bent-knee position to a straight-leg position. An example of knee extension is a simple kicking motion – whether that be kicking a football, soccer ball or an armed assailant.
- Knee Flexion. Knee flexion involves curling your leg backward by raising the heel of your foot toward the ceiling. The action of knee flexion is exemplified kicking yourself in the butt with the bottom of your foot.
- Transverse Hip Adduction. Moving your leg toward the center-line of your body, doing so on a horizontal plane and with your hip joint bent (i.e. the body position – not the movement – is similar to that when reclining in a Lay-Z-Boy). The movement is simply to bring the legs together.
Refer to the above list when reading about the individual muscle groups of the leg anatomy, below. While I will list the functions, I will not repeat the descriptions.
Now, let’s get to learning about the many muscles in the leg anatomy…
Quadriceps Femoris Anatomy
Quadriceps Muscles. The quadriceps muscles are the large muscles that make up the front of the thighs. This leg muscle group is popular – It’s what most people think of when they hear “leg anatomy.” This leg muscle group consists of these four individual muscles:
The Quadriceps Muscle Attachment Points. All four quadriceps muscles insert into the tibia (shin bone). And with one exception, they all originates from They all originate from the femur (thigh bone); that exception is the rectus femoris, which originates from the ilium (highest bone on the pelvis), which allows it to play a role in hip flexion.
Overall Quadriceps Functions. The quadriceps roles include:
- Knee Extension (main function).
- Hip Flexion.
Quadriceps Exercises. Examples of quadriceps-targeting exercises include:
Hamstring Muscles. The hamstring muscles, also known as the rear thighs, make up the backside of the upper leg anatomy. Like the quadriceps, the hamstring muscle group also contains four separate muscles:
The Hamstring Muscle Attachment Points. They all originate from the ischium (sitting bones), and insert into the tibia. That is, all except for the short head of the biceps femoris; it originates from near the head of the femur (thigh bone) and inserts into the fibula (calf bone).
Overall Hamstring Functions. They are mainly responsible for knee flexion as well as hip extension.
- Knee Flexion (main function)
- Internal Knee Rotation
- External Rotation
- Hip Extension
Hamstring Exercises. Examples of hamstring exercises include:
Gluteal Muscles. The gluteal muscles refer to the individual muscles of the glutes – which we all know is the fancy word for “butt” and its many other nicknames. The three main muscles of the glutes include:
Here’s a quick fun fact for you – The gluteus maximus is not only the largest muscle muscle in the leg anatomy, but it’s the largest in the entire body.
The Gluteal Muscles’ Attachment Points. The attachments of the gluteal muscles are relatively complex. Each muscle head originates from either the ilium (highest bone on the pelvis), lumbar fascia (thick sheet of fibrous muscle in the lower back), sacrum (a triangular bone at bottom of spine near the tailbone). And each muscle inserts into femur (thigh bone) or the iliotibial tract (the IT Band – a long fibrous tissue that travels down the femur).
Overall Functions of the Glutes. The major roles of the glutes are to perform:
- Hip Extension (main function)
- Hip Abduction
Glutes Exercises. The best exercises for targeting the gluteal muscles include:
Hip Abductor Muscles. These muscles are located on the outter thigh area of the leg anatomy. The hip abductors are not so much a muscle group as they are a “group of muscles,” so to speak. That is, “hip abductors” refers to the muscles involved in hip abduction. The hip abductors include:
- All 3 Gluteal Muscles
- Tensor Fasciae Latae
Hip Abductor Muscles’ Attachment Points. The attachment points for the gluteals were explained above. The tensor fasciae latae originates from the ilium (highest bone on the pelvis) and inserts into the tibia (shin bone).
Main Function of the Hip Abductors. Although the muscles that are considered to be hip abductors have other functions, their function in this context is – drumroll please….
- …Hip Abduction!
Hip Abductor Exercises. Leg exercises that directly target the hip abductors include:
- Cable Hip Abductions
- Lying Hip Abductions (Weighted or Bodyweight)
- Machine Seated Hip Abductions
- Machine Standing Hip Abductions
- [For the Tensor Fasciae Latae], see hip flexor exercises below
- [For the gluteal muscles], see glutes exerices above
Hip Adductor Muscles. The hip adductors are located on the inner thigh region of the leg anatomy. They are a small, specific muscle group that contains 3 individual muscles:
Hip Adductor Muscles’ Attachment Points. All three of the adductors originate from the pubis (pubic bone) and insert into the femur (thigh bones). Note that the posterior head of the adductor magnus inserts into the ischium (sitting bones).
Overall Function of the Hip Adductors. The roles of the hip adductors include:
- Hip Adduction (main function)
- External Rotation
- Hip Extension
- Hip Flexion
Hip Adductor Exercises. The best leg exercises for directly hitting the hip adductor muscles include:
- Cable Hip Adductions
- Lying Hip Adductions (Weighted or Bodyweight)
- Machine Seated Hip Adductions
- Machine Standing Hip Adductions
The Hip Flexors & Iliopsoas
Iliopsoas. The hip flexors refer to a group of muscles in the frontal-hip area of the leg anatomy. Although there are others, the iliopsoas is the main muscle group that is associated with the “hip flexors.”
- Psoas Major
The “Other” Hip Flexor Muscles You see, the hip flexors are more like a “group of muscles” rather than a muscle group – if that makes sense. For example the rectus femoris is officially a quadriceps muscle, although it’s grouped here due to it’s hip flexion function.
- Rectus Femoris (see quadriceps for pic)
- Tensor Fasciae Latae
Main Function of Hip Flexor Muscles. The Iliacus and the other muscles that make up the hip flexors have an array of functions. But the functions we care about in this context is, you guessed it…
- …Hip Flexion!
Hip Flexor Exercises. The exercises that most directly work the hip flexors include:
- Decline Sit Ups
- Knee Raises
- Leg Raises
- Quadriceps exercises such as squats or the leg press (for the rectus femoris)
Shortened, tight and inflexible hip flexors are on the rise. This is largely a result of the modern lifestyle, which is characterized by too much sitting and a lack of stretching. The result is flexibility issues, postural problems and lower back pain…
…But this doesn’t mean that you should avoid exercises that involve the hip flexor muscles. Instead you can counteract the hip flexor tightness by forming habits out of these two simple tips:
- Hip Flexor Stretches. Stretch your hip flexors at least 2-3 times a day (using a forward lunge position). Each time, stretch for 20-30 seconds per side, then repeat with the other side. Continue if desired.
- Get Up, Lazy Ass! You should also stand up every 15 to 30 minutes to break up long periods of sitting – even if just for a few seconds. This does make a real difference, and is backed up by the “Law of Repetitive Motion.”
Leg Anatomy Summary
This wraps up my synopsis of the leg anatomy. If you haven’t already done so, be sure to visit the links at the end of each of the above section to get an in-depth and satisfying understanding of each muscle group within the leg anatomy.