Video: Femur

Did you know that apparently every 11 seconds, someone somewhere around the world suffers a hip fracture? And this is becoming even more common due to the fact that the risk of hip fractures increases with age, and as our life expectancy rises and the population ages, the incidence of hip fractures tends to increase. But did you know that most hip fractures are actually fractures of the proximal end of the femur rather than the hip bone? Yes, indeed. Let's find out more now as we learn about all things related to the anatomy of the femur.

The femur forms the long bone of the thigh and is the longest and strongest bone in the body. As a long bone, the femur has a hard outer surface of compact bone and a mesh-like interior of spongy bone which contains bone marrow. It comprises a proximal end which articulates with the hip bone to form the hip joint, a body, and a distal end that articulates with the patella and the tibia to form the knee joint. It acts as the attachment site for many muscles of the hip and thigh and transmits body weight from the hip bone to the tibia when upright.

Now that we know where the femur is and what it does, let's take a closer look at the anatomical landmarks of the regions of the femur starting at the proximal end.

The proximal end of the femur is composed of a head, neck, as well as greater and lesser trochanters. The head of the femur forms the most proximal aspect of the femur. It articulates with the lunate surface of the acetabulum of the pelvis, forming a ball-and-socket synovial joint called the acetabulofemoral joint, or as it's more commonly known, the hip joint.

The surface of the head of the femur is smooth and coated with hyaline cartilage except in a medially-located area known as the fovea which is a depression for the attachment of the ligament of the head of the femur. Fovea in Latin means "pit" which is exactly what the small bony indentation represents.

The neck of the femur is distal to and continuous with the head of the femur. The neck of the femur connects the head with the body and is primarily covered by the fibrous joint capsule of the hip joint and its supporting ligaments. At the base of the neck of the femur are two femoral trochanters -- the lesser trochanter and the greater trochanter.

The lesser trochanter is a conical eminence of variable size projecting from the medial aspect of the proximal end of the femur. It forms the attachment site for the distal attachment for the iliopsoas muscle. The greater trochanter is a large, roughly quadrangular, palpable prominence on the superolateral aspect of the proximal end of the femur. It projects superiorly from the superior aspect of the junction between the neck and body of the femur.

The greater trochanter is the site of attachment for the following muscles: the gluteus medius and minimus; the piriformis, the obturator internus, and the superior and inferior gemelli. The medial surface of the greater trochanter presents with a deep depression known as the trochanteric fossa. The tendon of the obturator externus muscle inserts into this fossa.

The third trochanter is a variably present round bony projection adjacent to the proximal aspect of the gluteal tuberosity of the proximal end. When present, it functions to provide an additional attachment site for the ascending tendon of the gluteus maximus muscle.

The intertrochanteric line is a ridge located along the anterior aspect of the junction of the femoral neck and shaft. It traverses between the apex of the greater trochanter and to a small tubercle on the distal part of the lesser trochanter and functions as an attachment point for the joint capsule of the hip, the iliofemoral ligament, and the vastus medialis and lateralis muscles.

Not to be confused with the intertrochanteric line, the intertrochanteric crest is a bony elevation on the posterior aspect of the proximal end which marks the transition between the neck and the body of the femur. It extends from the greater trochanter superolaterally to the lesser trochanter inferomedially. It forms the posterior part of the attachment for the joint capsule of the hip.

Approximately halfway across the intertrochanteric crest is a bony protuberance known as the quadrate tubercle. The quadrate tubercle forms the insertion site of the quadratus femoris muscle.

Now that we have explored the features of the proximal end, it's time to take a look at the body side of the femur.

The body of the femur, also known as the shaft of the femur, is bowed anteriorly which contributes to its weightbearing capacity. Extending along the posterior surface of the body of the femur is a broad ridge known as the linea aspera which translates to "rough line," perfectly describing this structure. The linea aspera divides the posterior surface of the femur into medial and lateral halves. It consists of medial and lateral lips with a narrow intermediate zone that extends between them.

The linea aspera functions as an attachment site for many important muscles of the thigh. It provides an origin or proximal attachment for the vastus medialis, vastus lateralis, and the short head of the biceps femoris muscle. It is also an insertion or distal attachment for the adductor brevis, longus, and magnus muscles, and finally acts as an attachment site for both the medial and lateral femoral intermuscular septa. The linea aspera terminates proximally by merging with the pectineal line and gluteal tuberosity, and inferiorly, as it divides into the medial and lateral supracondylar lines all of which we will look at now.

The gluteal tuberosity is a bony ridge which extends in a superolateral direction from the lateral lip of the linea aspera towards the greater trochanter. It acts as an attachment site for the gluteus maximus as well as the adductor magnus and minimus muscles. Extending proximally from the medial lip of the linea aspera is the pectineal line which extends in a superomedial direction towards the lesser trochanter. As its name suggests, the pectineal line forms an attachment site for the pectineus.

Next is the spiral line, one of the lesser known landmarks of the femur. It can be described as a continuation of the intertrochanteric line, which we saw earlier, that courses, or spirals, just below the lesser trochanter from anterior to posterior, towards the medial lip of the linea aspera. It provides a proximal attachment point for the vastus medialis muscle and sometimes also the iliopsoas muscle. The spiral line is often confused with the pectineal line due to its proximity with it.

Moving distally, the medial and lateral lips of the linea aspera diverge once again to form the medial and lateral supracondylar lines. The medial supracondylar line extends from the medial lip of the linea aspera to the adductor tubercle. It acts as a distal attachment site for the vastus medialis and adductor magnus muscles.

The lateral supracondylar line arises as an inferior continuation of the lateral lip of the linea aspera and is the more pronounced of the two supracondylar lines. It provides an attachment for the plantaris muscle and the short head of the biceps femoris muscle.

The popliteal surface of the femur is the smooth triangular area between the medial and lateral supracondylar lines. It contributes to the floor of the popliteal fossa and functions as an attachment site for the medial head of the gastrocnemius muscle.

The final part of the femur is its distal end, which we'll take a look at next.

The distal end of the femur extends from the body and expands to form a trapezoidal shape. It is characterized by the medial and lateral condyles which articulate with the tibia and patella to form the knee joint. The medal condyle of the femur is the shorter bony eminence of the distal femur. It articulates with the medial condyle of the tibia via the medial meniscus forming the medial femorotibial joint, a component of the knee joint.

The superomedial aspect of the medial condyle presents with a small bony prominence known as the adductor tubercle. It lies at the inferior end of the medial supracondylar line and provides an insertion site for the adductor magnus muscle.

Distal to the adductor tubercle is a rough eminence on the medial aspect of the medial condyle of the femur known as the medial epicondyle. The medial epicondyle of the femur provides the attachment site for one of the ligaments of the knee joint, the tibial collateral ligament. The lateral condyle is the longer round eminence of the distal femur. It articulates with the lateral condyle of the tibia via the lateral meniscus to form the lateral femorotibial joint.

Another bony landmark on the lateral condyle of the femur is the groove for the popliteus muscle, which is located distal to the lateral epicondyle of the femur. It is a smooth, curved depression which, as its name suggests, allows for the passage of the tendon of the popliteus muscle.

The distal portion of the femur also articulates with the patella, forming the patellofemoral joint, which completes the knee joint. The part of the femur that articulates with the patella is simply known as the patellar surface of the femur. It is a grooved area on the anterior aspect of the distal end of the femur and is located between the articular surfaces of the medial and lateral condyles.

On the posterior aspect of the distal femur is the intercondylar line which is a horizontal ridge which extends between the medial and lateral condyles along the distal border of the popliteal surface. It provides an attachment site for the capsular ligaments of the knee joint and the oblique popliteal ligament.

Distal to the intercondylar line is a shallow depression known as the intercondylar fossa. Its walls are formed by the opposing aspects of the medial and lateral condyles and provide an attachment site for the cruciate ligaments of the knee.

Now that you have a good understanding of the landmarks and associated articulations of the femur, it's time to apply this knowledge to a clinical scenario.

So remember at the beginning of this tutorial, we mentioned that the elderly are more susceptible to hip fractures. Well, this is usually secondary to trauma. In younger patients, high energy trauma like car accidents can lead to these fractures, but in the elderly, low energy trauma like simply falling from standing height can cause neck or femur fractures.

Patients who have fractured their femur present with significant pain and inability to bear weight on the affected leg. On examination, the leg is shortened and externally rotated. Because the arteries that supply the femoral head are in close proximity to the neck of the femur, a fracture here can also lead to avascular necrosis or lack of blood supply to the head of the femur. The surgeons would usually order x-rays to assess the damage and confirm their diagnosis. Management of these patients is initially analgesia to help with the excruciating pain. The definitive management is surgery.

And that's a wrap on all things femur! Fantastic work! To review everything you learned today, check the quiz and atlas galleries in our study unit.

We hope you enjoyed this tutorial, and can't wait to see you next time. Happy studying!