The thigh is the region of the lower limb located between the hip and the knee. It plays a crucial role in supporting the body’s weight and facilitating movement. The thigh is composed of various structures including bones, muscles, blood vessels, and nerves.
The thigh’s structure allows for a wide range of motion at the hip and knee joints, enabling activities such as walking, running, jumping, and sitting. The strength and stability of the thigh are crucial for mobility and balance.
Bones: The femur or the thighbone is the only bone in the human thigh. It is the longest and strongest bone in the body, designed to withstand the high stresses of weight-bearing and locomotion.
Muscles: There are three main groups of muscles in the thigh:
Quadriceps Femoris: Composed of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. These muscles are primarily responsible for knee extension and hip flexion (rectus femoris).
Hamstrings: Composed of the biceps femoris, semitendinosus, and semimembranosus. These muscles are primarily responsible for knee flexion and hip extension.
Adductors: Composed of the adductor magnus, adductor longus, adductor brevis, gracilis, and obturator externus. These muscles are primarily responsible for adduction of the thigh at the hip joint.
Ligaments: The primary ligaments in the thigh are located at the hip joint (iliofemoral, ischiofemoral, and pubofemoral ligaments) and the knee joint (anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments).
Fascial Compartments: The thigh has three fascial compartments, each containing a group of muscles with similar functions:
Anterior Compartment: Contains the quadriceps and is responsible for knee extension.
Medial Compartment: Contains the adductors and is responsible for adduction of the thigh.
Posterior Compartment: Contains the hamstrings and is responsible for knee flexion and hip extension.
Blood Vessels: The main artery of the thigh is the femoral artery, which supplies oxygenated blood to the thigh’s tissues. The femoral vein runs parallel to the artery and carries deoxygenated blood back to the heart.
Nerves: The femoral nerve innervates the anterior compartment of the thigh, while the obturator nerve innervates the medial compartment. The sciatic nerve innervates the posterior compartment and is the largest nerve in the body.
Fascia: The thigh is encased in a tough connective tissue known as the fascia lata. This fascia helps to compartmentalize and support the structures within the thigh.
Joint Anatomy The femur articulates with the pelvis at the hip joint and with the tibia at the knee joint. Both the hip and knee are synovial joints, allowing for a great deal of movement.
Bursa Sacs: These are small fluid-filled sacs that provide cushioning and reduce friction between the bones, tendons, and muscles. Notable bursae in the thigh include the trochanteric bursa, iliopsoas bursa, and several bursae around the knee.
Kinesiology: The thigh plays a vital role in locomotion, providing power and control for walking, running, and jumping. This includes actions such as:
Hip Flexion and Extension: Lifting the leg forward (flexion, primarily by the iliopsoas and rectus femoris) and backward (extension, primarily by the hamstrings and gluteus maximus).
Hip Abduction and Adduction: Moving the leg away from the midline of the body (abduction, primarily by the gluteal muscles) and toward the midline (adduction, primarily by the adductor group).
Knee Flexion and Extension: Bending (flexion, primarily by the hamstrings) and straightening (extension, primarily by the quadriceps) the knee.
Knee Rotation: Some degree of rotation is also possible at the knee when it is flexed, due to the articulation between the femur and the tibia.