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Anatomy and function of the thigh bone.
Hey everyone! This is Nicole from Kenhub, and in this tutorial, we're going to be looking at the femur.
So, as we can see in this lovely image of the femur highlighted in green, the femur is a long bone of the lower limb, and we can see it connecting with the acetabulum of the hip joint here and down here, we've got the tibia with the patella resting on top. And as we can see, it is the longest and strongest bone of the body. It's also the attachment site for many muscles of the hip and leg and as it must do being the major bone of the leg, it can withstand pressure from multiple angles.
As a long bone, the femur has a hard outer surface of compact bone and a mesh-like interior of cancellous bone which contains bone marrow. And if you remember the other bones I pointed out before – that is the pelvis, the patella and the tibia – well, we're going to point out some of the joints they create right now.
So, here we have the head of the femur at the proximal end of the femur which slips into the acetabulum of the pelvis to form the acetabulofemoral joint also known as the hip joint while distally, we have the femur which forms the tibiofemoral joint with the tibia, and here we have the patellofemoral joint with the patella.
And in this tutorial, we're going to review the anatomical features of the three parts of the femur – the upper extremity, the shaft and the lower extremity.
The upper extremity of the femur is comprised of the head, the neck, the lesser trochanter and the greater trochanter. The head of the femur is situated in the most proximal aspect of the femur. It articulates with the lunate surface of the acetabulum of the pelvis which is now highlighted in green creating a ball-and-socket synovial joint called the acetabulofemoral joint or the hip joint. And the surface of the head of the femur is smooth and coated with hyaline cartilage except in an area called the fovea capitis femoris which is a depressed site for the attachment of the ligament of the head of the femur.
Now we're looking at an image of the neck of the femur, and the neck of the femur is inferior to and continuous with the head of the femur situated between the head and the two femoral trochanters – the lesser trochanter and the greater trochanter. And the neck of the femur connects the upper extremity of the femur with the shaft and is covered by the fibrous joint capsule of the acetabulofemoral joint and its supporting ligaments. And just to connect our femur with some clinical notes, in the case of a fracture to the neck of the femur, the blood supply through the neck of the femur to the shaft and lower extremity of the femur may become insufficient and result in avascular necrosis.
The lesser trochanter is, as we can see, a conical eminence of variable size projecting from the superomedial surface of the upper extremity of the femur and it's somewhat connected to the greater trochanter by the intertrochanteric line as we can see in the image just here. Now, the lesser trochanter is the attachment site for the iliofemoral ligament, the proximal fibers of the vastus lateralis and the vastus medialis muscles, the iliopsoas muscle and the superior portion of the adductor magnus muscle. And these muscles tend to be attached to those down the length of the femur or in the case of the iliopsoas from the femur to the spine.
And now we're at an image of the greater trochanter, and the greater trochanter is a large palpable prominence on the superolateral aspect of the upper extremity of the femur, and it's the site of attachment for quite a few muscles and I'm going to list them for you now. So they are the gluteus medius, the gluteus minimus, the piriformis, the obturator internus, the obturator externus, the superior gemellus and the inferior gemellus, and most of these muscles connect the femur to the pelvis in some way.
The shaft of the femur is situated between the upper and lower extremities of the femur and is continuous with both, and the shaft is somewhat cylindrically shaped and slightly broader superiorly and inferiorly with a thinner middle section as we can see in this image. And there are three notable surface features of the shaft of the femur and these are the pectineal line which is a medially situated ridge that curves inferiorly from the lesser trochanter, and the pectineal line is important because it is the site of attachment for the pectineus muscle; the gluteal tuberosity which is a laterally situated ledge that courses inferiorly along the superoposterior surface of the shaft, and this is the site of attachment for the deep distal fibers of the gluteus maximus muscle – so that's important to note as well. The pectineal line and the gluteal tuberosity converged to form a prominent longitudinal ridge on the posterior aspect of the femur and you can see this pointed out with my arrow on the slide just here. Now, this ridge has another name and its name is the linea aspera, and the linea aspera is the site of attachment for the adductor longus muscle, the short head of the biceps femoris muscle and the intermuscular septa – so that's also an important line to know. And just looking at our image here, just note that the shaft of the femur descends at a seven degree angle medially from the vertical axis.
Now we're looking down the bottom at our lower extremity of the femur. And the lower extremity of the femur articulates with the tibia and the patella forming the tibiofemoral joint and the patellofemoral joint. As we can see, it contains two condyles – a medial condyle and a lateral condyle. Posteriorly, there is a deep smooth notch separating the condyles and this is called the intercondylar fossa while anteriorly, the condyles are more prominent and separated from one another by the patellar surface. And of course, the medial condyle of the femur articulates with the articular surface of the medial condyle of the tibia while the lateral condyle of the femur articulates with the articular surface of the lateral condyle of the tibia.
And as before, the condyles are covered with a thick layer of hyaline cartilage which of course helps with the movement of the joint. And superior to the condyles are bony prominences and this is the medial epicondyle which is the point of origin for the medial or tibial collateral ligament and over here, we have the lateral epicondyle which is the point of origin for the lateral or the fibular collateral ligament.