Quadriceps femoris muscle
The quadriceps femoris muscle translates to “four-headed muscle” from Latin. It bears this name because it consists of four individual muscles; rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius. Out of all four muscles, only the rectus femoris crosses both the hip and knee joints. The others cross only the knee joint. These muscles differ in their origin, but share a common quadriceps femoris tendon which inserts into the patella. The function of the quadriceps femoris muscle is to extend the leg at the knee joint and to flex the thigh at the hip joint.
This article will discuss the anatomy and function of the quadriceps femoris muscle.
- Rectus femoris
- Vastus medialis
- Vastus lateralis
- Vastus intermedius
- Quadriceps femoris tendon
- Clinical notes
Origin and insertion
The rectus femoris is a fusiform muscle that consists of two heads. It originates from two sites on the ilium; the anterior inferior iliac spine (straight head) and supraacetabular groove (reflected head). The two heads unite into a common muscle belly that courses down the thigh in an almost vertical fashion, covering the anterior aspect of this region.
The muscle fibers converge towards a thick tendon which inserts into the base of patella. Occasionally, the rectus femoris can have a third head that originates from the iliofemoral ligament.
The quadriceps femoris muscles are a big topic to learn! Feeling a bit overwhelmed? Learn the attachments, innervations and functions of these muscles faster and easier with our lower extremity muscle chart.
The proximal part of rectus femoris muscle lies deep to tensor fasciae latae, sartorius and iliacus muscles. All the contents of the anterior compartment of the thigh lie deep to rectus femoris. These include the capsule of the hip joint, vastus intermedius, anterior margins of vastus lateralis and vastus intermedius, lateral circumflex femoral artery and some branches of the femoral nerve.
The rectus femoris muscle is supplied by the artery of the quadriceps, which can stem from three sources; femoral, deep femoral or lateral circumflex femoral arteries. The lateral circumflex femoral and superficial circumflex iliac arteries also contribute to the blood supply of rectus femoris, but to a lesser extent.
Origin and insertion
The vastus medialis muscle originates from several landmarks of the proximal femur; the inferior part of the intertrochanteric line, pectineal line of femur, medial lip of linea aspera and proximal half of the medial supracondylar line. It descends obliquely through the thigh, with its fibers spiraling around the long axis of the muscle.
The lowermost fibers lie in an almost horizontal plane, forming a noticeable bulge superior to the medial side of the patella. This particular part of vastus medialis is often referred to as the vastus obliquus by some authors. Finally, the muscle inserts into the base of patella via the quadriceps femoris tendon. Some of its tendinous fibers continue downwards and insert into the medial condyle of tibia.
Vastus medialis lies medial to rectus femoris and is partially covered by it. The sartorius muscle also crosses the superficial surface of vastus medialis. In the middle third of the thigh, vastus medialis forms the lateral wall of the adductor canal (Hunter’s canal). This canal is completed by adductor longus and adductor magnus posteriorly, and by sartorius medially. It transmits the femoral artery, femoral vein, saphenous nerve and nerve to vastus medialis (both being branches of femoral nerve).
Vastus medialis is supplied by three muscular branches of the femoral artery. It also receives some minor contributions from the deep femoral and descending genicular arteries.
Origin and insertion
Vastus lateralis is the largest of all four quadriceps femoris muscles. It originates via a broad aponeurosis from various sites on the femur, such as the proximal half of the intertrochanteric line, anterior and inferior borders of the greater trochanter, lateral lip of the gluteal tuberosity and proximal half of the lateral lip of linea aspera. The aponeurosis overlies the upper three-quarters of the muscle, with many muscle fibers originating from its deep surface.
The muscle descends through the lateral part of the anterior thigh compartment and inserts to the base of patella via the quadriceps tendon. Some of its tendinous fibers descend all the way to the proximal tibia and blend with the iliotibial tract to insert into the lateral condyle of tibia.
The vastus lateralis muscle lies superficial to the biceps femoris muscle, from which it is separated by the lateral intermuscular septum. The lateral side of the muscle is covered by the tensor fasciae latae and gluteus maximus. Its medial surface is related to vastus intermedius, from which it is separated by the lateral femoral circumflex artery and branches of the femoral nerve.
Vastus lateralis receives its blood supply from three sources;
- The superior medial artery, which is a branch of the lateral circumflex femoral artery.
- The inferior medial artery, a branch of the artery of the quadriceps.
- The lateral artery, which is actually the first perforator of the deep femoral artery.
Origin and insertion
The vastus intermedius muscle lies between vastus lateralis and vastus medialis. It originates from the anterior surface of the femur, more specifically from the proximal two-thirds of its shaft. The muscle descends over the anterior surface of femur, filling the interval between vastus medialis and lateralis. It gives off a wide aponeurosis at the level of the distal femur, via which it attaches to the base of patella via the common quadriceps tendon. It also inserts into the lateral condyle of tibia.
Vastus intermedius is completely surrounded by the other muscles of the quadriceps femoris. Rectus femoris covers its anterior surface, while vastus lateralis and medialis lie on its lateral and medial surfaces, respectively.
The blood supply to the vastus intermedius comes from the artery of the quadriceps and deep femoral artery.
Quadriceps femoris tendon
The quadriceps femoris tendon is a common tendon via which the four components of the quadriceps femoris muscle insert to the base of patella.
- The tendon of the rectus femoris muscle contributes to the superficial central part of the quadriceps tendon.
- The tendon of vastus medialis makes up the superficial medial part of the quadriceps tendon.
- The tendon of vastus lateralis comprises the superficial lateral part of the quadriceps tendon.
- The tendon of vastus intermedius makes the deep part of the quadriceps tendon.
The tendon of quadriceps continues distally and blends with the patellar ligament which attaches to the tibial tuberosity. This significantly contributes to the stability of the patella and knee joint.
The entire quadriceps femoris muscle is innervated by the femoral nerve (L2-L4).
Quadriceps femoris is the most powerful extensor of the knee. All four of its components are capable to extend the knee, however, they do so in different directions. Rectus femoris muscle aligns with the mechanical axis of the lower limb and pulls the patella along this axis. However, the remaining muscles originate from femur, meaning that their pull is oriented both proximally and laterally. This is where the vastus obliquus (the above-explained part of vastus medialis) is extremely important. Its horizontally oriented fibers counter the pull of the three vasti, contributing to the stability of the knee during extension and preventing the dislocation of the patella.
Aside from extending the knee, the rectus femoris muscle exhibits additional actions since it crosses both the hip and knee joints. By acting on the hip joint, it helps with thigh flexion. When its patellar attachment is fixed, this muscle aids to flex the pelvis anteriorly towards the thigh. Rectus femoris is also capable of simultaneously flexing the hip and extending the knee.
Clinical analysis of the quadriceps group involves extending the knee against resistance, in the supine position with the hip flexed.
The knee jerk or patellar reflex is a clinical test involving the patellar ligament. It tests spinal cord segments L2, L3, and L4. Striking the patellar ligament causes it to stretch, activating the muscle spindle stretch receptor in the quadriceps femoris muscle. The stretch causes activation of a reflex arc, which cause the quadriceps femoris muscles to contract and oppose the stretch of the tendon. The sensory input from the force applied to the patellar ligament is relayed back to the spinal cord through the L2, L3 and L4 spinal nerves. The sensory stimulus is processed at this level of the spinal cord, and as these roots are the same as the motor roots for the quadriceps femoris muscle (i.e. the femoral nerve), a motor stimulus is relayed through the same spinal nerve roots to the muscle causing it to contract. This is an important mechanism in maintaining balance. If there is an overstretch in the patellar ligament in real life situations, for example, when overbalancing backwards, the reflex arc is activated, and causes a contraction of the quadriceps muscle to extend the knee and correct the overbalancing. This prevents the person from falling backwards. Absence of the patellar reflex could indicate could indicate a lesion to the spinal cord at the level of the nerves that innervate the quadriceps femoris muscle (L2, L3, and L4). Such injuries are usually caused by physical trauma, one of the leading causes being road traffic collisions. These injuries are considered irreversible, so treatment entails mainly physical therapy techniques in order to maintain and strengthen existing function of the muscles.
As it is an extremely large muscle mass, the muscles of the anterior thigh are also susceptible to contusions, specifically in individuals that participate in high impact sports. A contusion causes bleeding from capillaries and blood infiltration into the muscle and surrounding soft tissues. They are commonly referred to as a bruise. These usually do not require medical attention, and heal on their own over time.