thigh muscles

Posterior view Anterior view

• Rectus femoris is located in the anterior compartment of the thigh.
• The muscle has two heads which originate from sites on the ilium (part of the pelvis)
• The two heads unite to form a long muscle that runs down the thigh and then inserts into the patella via the quadriceps tendon
• Rectus femoris is part of the quadriceps group of muscles which work together to create the action of knee extension.
• Rectus femoris also contributes to hip flexion.

Rectus Femoris Muscle

The quadriceps muscles are the prime movers in knee extension. The four quadriceps muscles work together to move the knee from a flexed posiiton to an extended position.The quadriceps are assisted during knee extension by tensor fascia latae.During extension the patella glides over the patellar surface of the femur. The patella acts as a pulley for the quadriceps muscles providing greater force.

Knee Extension

• Vastus lateralis originates from the femur via a flat sheet of connective tissue
• The muscle travels down the leg and inserts into the patella via the quadriceps tendon.
• Vastus lateralis is the largest of the quadriceps group of muscles.
• The quadriceps muscles work together to create the action of knee extension.

Vastus Lateralis Muscle

• The tensor fascia latae (TFL) muscle is located on the lateral aspect of the thigh.
• The TFL originates from the iliac crest (part of the pelvis) and travels down the leg to form the iliotrbial tract (IT band).
• The IT band eventually inserts into the tibia.
• The TFL assists the quadriceps with knee extension and contributes to external rotation of the knee.
• The TFL is also involved in internal rotation of the hip.

Tensor Fascia Latea Muscle

Vastus Medialis Muscle

• Vastus medialis is a large muscle in the anterior compartment of the thigh.
• The muscle originates from the proximal part of the femur, descends down the thigh before inserting into the base of the patella via the quadriceps tendon.
• Vastus medialis is part of the quadriceps group of muscles.
• The quadriceps muscles work together to create the action of knee extension.

• The sartorius muscle is located in the anterior of the thigh.
• Sartorius originates from the iliac spine (part of the pelvis) and crosses the thigh inserting into the tibia below the knee.
• Sartorius contributes to flexion and internal rotation of the knee.
• Sartorius also contributes to flexion, abduction and external rotation at the hip.

Sartorius Muscle

• The gracilis muscle is a long slender muscle.
• It is the most medial and superficial muscle of the thigh.
• The muscle extends from the pubis to the tibia.
• Function: supports flexion and internal rotation of the knee. It is also involved in hip adduction.

Gracilis Muscle

• Vastus intermedius sits between vastus lateralis and vastus medialis and deep to rectus femoris.
• The muscle originates from the surface of the femur, descends the thigh, and inserts into the patella via the quadriceps tendon.
• Vastus intermedius is part of the quadriceps group of muscles.
• The quadriceps muscles work together to create the action of knee extension.

Vastus Intermedius Muscle

The knee joint allows limited external or lateral rotation when “unlocking” and flexing the knee.External rotation of the knee is created by contraction of the biceps femoris muscle which is part of the hamstrings muscle group.

Knee External Rotation

Being a hinge joint, the main movements in the knee joint are flexion and extension of the knee. The knee joint also allows limited internal or medial rotation when in a flexed position and in the last stage of extension.Internal rotation is created by contraction of the popliteus muscle as well as two of the hamstrings muscles - semi membranosus, and semi tendinosus.Internal rotation is assisted by the action of the sartorius and gracilis muscles

Knee Internal Rotation

Popliteus is a small muscle that sits behind the knee in an area known as the popliteal fossa.The popliteus muscle extends from the femur to the tibia.Popliteus has an important role in initiating flexion of the knee when it is fully extended or "locked".Additionaly, the popliteus muscle is the main stabilizer of the posterior knee region.

Popliteus Muscle

Biceps femoris is located in the posterior aspect of the thigh. The muscle is part of the hamstrings muscle group along with the semitendinosus and semimembranosus muscles.The biceps femoris muscle runs from the ischial tuberosity (part of the pelvis), all the way to the proximal part of the fibula.Biceps femoris creates flexion and external rotation at the knee joint.The muscles also acts on the hip joint contributing to extension and external rotation.

Biceps Femoris Muscle

Posterior view Lateral view

Semimembranosus is part of the hamstrings muscle group in the posterior thigh. It runs deep to semitendinosus and medial to biceps femoris.Semimembranosus originates from the ischial tuberosity of the pelvis and inserts into the medial condyle of the tibia.Semimembranosus flexes and internally rotates the leg through the knee joint. Semimembranosus also extends and causes internal rotation of the hip.

Semimembranosus Muscle

Semitendinosus is a long muscle in the posterior thigh, it sits medially to biceps femoris.The muscle extends from the ischial tuberosity of the pelvis to the end of the tibia below medial condyle.Semitendinosus main functions are to contribute to flexion of the knee and to assist in stabilising the knee joint. When the knee is semiflexed, semitendinosus contributes to internal rotation of the knee.

Semitendinosus Muscle

The hamstring muscles are the prime movers in knee flexion. The three hamstring muscles work together to move the knee from an extended posiiton to a flexed position. The quadriceps are assisted during knee extension by sartorius, gracilis, and gastrocnemius (one of the posterior calf muscles).During flexion the patella glides over the patellar surface of the femur. The patella acts as a pulley for the hamstrings muscles providing greater force.

Knee Flexion