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The muscles of the thigh are responsible for a variety of movements, acting on both the hip and the knee joint. There are many muscles in the thigh, however, they can be categorised into the anterior, posterior and medial compartments.
These compartments are separated by layers of fascia.
It is also very important when studying muscles that you are comfortable with anatomical terminology, as a lot is used in these articles. For more information, please check out our Anatomical Terminology Article.
Diagram - The fascial compartments of the thigh. Pink represents the anterior compartment, green is the medial compartment and blue represents the posterior compartment
Public Domain Image [Public domain]
The muscles of the anterior compartment of the thigh are innervated by the femoral nerve. Generally speaking, these muscles act to flex the thigh at the hip joint and can also act on the knee joint.
Diagram - Muscles of the anterior thigh. Note that the vastus intermedialis tucked underneath the rectus femoris and is, therefore, not visible
Creative commons source by OpenStax College [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
This muscle is the longest in the body and runs in an oblique fashion across the anterior thigh. It is long, thin and is the most superficial of the anterior compartment muscles. It runs from the anterior superior iliac spine and runs inferomedially to the medial tibia.
It flexes, abducts and laterally rotates the hip joint and flexes the knee joint.
This is a flat muscle that runs from the anterior surface of the pubis to the pectineal line of the femur. Its placement within the body allows it to flex and adduct the hip joint.
There are three vastus muscles that contribute the quadriceps femoris group of muscles. These muscles are responsible for extension of the knee joint. They all attach to the patella via the patellar ligament. There are three vastus muscles:
- Vastus Lateralis - originating from the lateral lip of the linea aspera
- Vastus Intermedius - originating from the anterior surface of the femoral shaft
- Vastus Medialis - originating from the medial lip of the linea aspera
This muscle makes up the fourth muscle of quadriceps femoris. It originates from the ilium and attaches to the patella, then to the tibial tuberosity via the patellar ligament. It flexes the hip and extends the knee.
This muscle is a combination of both the psoas major and iliacus muscles, hence the name.
They contribute to flexion of the hip joint.
Thankfully, the posterior compartment is simpler. Collectively, these muscles are known as the hamstrings and are involved with extension of the hip and flexion of the knee. They are innervated by the sciatic nerve.
Diagram - Posterior compartment (Hamstring) muscles on the right leg highlighted in red
Creative commons source by OpenStax College, edited by Dr. Thomas Burnell [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
This muscle has two heads. The long head originates at the ischial tuberosity, whilst the short head originates at the linea aspera of the femur. Together, they insert into the head of the fibula. This tendon can be palpated on the lateral aspect of the posterior knee. The two heads are innervated by two different branches of the sciatic nerve: the long head by the tibial branch, and the short head by the common fibular branch. It can contribute to some lateral rotation of the hip and the knee, as well as extension of the hip and flexion of the knee.
This muscle lies medial to the biceps femoris. It originates from the ischial tuberosity and attaches to the medial tibia. It is primarily responsible for flexion of the knee joint and extension of the hip, but can also medially rotate the thigh. It is innervated by the tibial branch of the sciatic nerve. When looking at the back of the thigh, it can be difficult to differentiate between semitendinosus and semimembranosus - semitendinosus is the one with a very long tendon at the bottom that attaches to the medial tibia.
This is the most medial of the posterior muscles. It is deep to the semitendinosus muscle. Like the other hamstrings, it originates from the ischial tuberosity. It attaches to the medial tibial condyle. In addition to extension of the hip and flexion of the knee, it can medially rotate the thigh. When looking at the back of the thigh, it can be difficult to differentiate between semintendinosus and semimembranosus - semimembranosus is the most medial of the hamstrings (both 'm' words).
These muscles are generally involved in hip adduction. They are innervated by the obturator nerve.
Diagram - Medial compartment of the thigh. Note that the Obturator Externus is not illustrated, but would be deep to pectineus and superior to adductor muscles
Creative commons source by Beth ohara, edited by Dr. Thomas Burnell [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
These are a group of muscles found in the medial thigh. They are primarily responsible for hip adduction and originate from the pubis. There are three muscles in this group:
- Adductor brevis - a short muscle that lies beneath adductor longus. It attaches to the linea aspera on the posterior femur.
- Adductor longus - a long, fan-shaped muscle that inserts into the middle third of the linea aspera.
- Adductor magnus - the largest muscle in the medial compartment. It is also the most deep of all the medial compartment muscles. This muscle can be divided into two regions, an adductor region and a hamstring region. The adductor region contributes to hip flexion whilst the hamstring region contributes to hip extension.
Obturator Externus is the most superior of the medial compartment muscles. It attaches to greater trochanter, and originates from the membrane covering the obturator foramen (the big hole in the pelvis made by the ischium and pubis). In addition to adduction, it also contributes to lateral rotation of the thigh.
The most superficial and most medial of the muscles in the medial compartment. It originates from the pubis and descends to the medial surface of the tibia. It, therefore, also contributes to flexion of the knee in addition to hip adduction.
For Pathologies and Conditions affecting the Thigh area, check out our Conditions of the Thigh article.
Edited by: Dr. Marcus Judge and Dr. Maddie Swannack
In this article
Learn the anterior, medial and posterior thigh muscles, their origins, insertions, actions and nerve supply, with clear anatomy diagrams.
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