Long Bones: Femur

Which way is up?

Whenever you look at a bone, you should orient it as it would be viewed in the anatomical positionA standard reference position where the body stands upright, facing forward, with arms at the sides. The patient should be standing erect with face, palms, and feet forward.  Creating this internal 3D image will help you determine if you have a right or a left femurThigh bone; longest and strongest bone in the body; has a large round head and prominent trochanters.  To approach this, we have to identify which side of this bone is the lateralAway from the midline of the body. side. Next, determine which side is the medialToward the midline of the body side.  You know that this headRounded proximal end that fits into the acetabulum of the hip bone. attaches to the hip. Therefore, the side with the head is the medial side of the bone.  However, just knowing medial and lateral doesn’t help. We haven’t determined if you have a picture of the posterior side. We also haven’t determined if it is of the anteriorThe front of the body or toward the front when standing in the anatomical position. side of a femur.  

Anterior Femur

I like to start with the femur. Students generally know that this knob here is called the head. The head is where the femur fits into the hip or coxal boneHip bone formed by fusion of ilium, ischium, and pubis; one on each side of pelvis..  The head of the femur is what articulates with the hip bone. It connects to make that ball-and-socket hip joint everyone’s always breaking.  The head is connected to the shaft of the bone via the neckNarrow region just below the head; common fracture site..  Seriously…it’s called the neck.  This is called the proximalCloser to the point of attachment or origin. end of the bone. The part of the femur that connects to the tibiaShinbone; large, weight-bearing medial bone of the lower leg. is called the distal end. This is where the knee is formed.

The patellaKneecap; small triangular bone embedded in quadriceps tendon; protects knee joint. or knee cap slides over the front of the femur every time you bend your knee.  Put your hand on your knee. Flex and extend your knee. Move the bottom part of your leg away from and to your body. As you move your knee you can feel the movementA fundamental property of life involving motion of the body or its parts. of your patella along the femur.  Actually, as you move your femur, the patella stays in place. The femur slides along the patella.  The movement of the patella creates a very smooth surface called the patellar surfaceSmooth anterior groove where the patella glides during knee movement.. This surface is only on the anterior side of the bone. 

Posterior Femur

On the posterior side of the bone is a very deepAway from the surface of the body. depression called a fossa.  This fossa is called the intercondylar fossaDeep notch on posterior distal femur between the condyles..  Why would someone name it that?  Well…because it is between these two big knobs that you have here that are called condyles.  This shallow depression is called a fossa, which means “basin.” It is located between these two knobs called condyles. Therefore, it is the intercondylar fossa.  Note how different it is that the patellar surface. It is a much deeper depression and appears darker on 2D pictures due to shadowing.

Now that we know which side of this bone is anterior and posterior, we can fill in some gaps about those condyles. We also know which side is medial and lateral. A condyle is a projection that is a knob-like structure that connects one bone with another.  A condyle is not a head of a bone.  Condyles are not pronounced as the completely rounded head of the femur.  These distal condyles of the femur just kind of sit on the plateaued top of the tibia (shin bone).  If you broke a condyle on your femur, someone might ask, “Which one?”  You have two condyles on one femur…how do you tell them apart.  The medial condyleInner rounded bump at distal end; articulates with tibia and meniscus. is on the side with the head.  The head is always medial.

Right Posterior Femur

The head and the condyles are sites of articulation or joining with other bones.  Articulation is a fancy word for joint.  Muscles complete the movement around an articulation. For muscles to enable movement, they must attach to the bones somewhere.  Muscle attachments are usually projections. The femur has three important places. Tendons extend from muscles in these areas and attach them to bone. 

The femur has trochanters, a word which means “to run.”  These are attachment points for the tendons of your large hip and quadricep muscles.  The greater trochanterLarge lateral projection near the head; palpable on the side of the hip. is on the superiorAbove or toward the upper part of the body. side of the neck. In contrast, the lesser trochanterSmaller medial projection below the head; muscle attachment site. is completely inferiorBelow or toward the lower part of the body. to the head and neck.  It’s important to recognize these from both sides of the bone: anterior and posterior.  Some pictures don’t do the placement of the trochanters justice.
 I highly recommend using the virtual 3D skeleton to rotate a femur and see the trochanters. 

Visible only on the posterior side, however, is the linea asperaProminent ridge running down posterior shaft; attachment for thigh muscles..  This, as well, is an attachment point for muscles.