The femur is the only bone in the thigh and is the longest bone in the human body. It houses numerous muscles and ligaments, and its three separate parts are referred to as the proximal, shaft, and distal. In the following article, we shall explore its anatomical features, its attachments, bony landmarks, and their clinical correlations.
The proximal aspect of the femur articulates with the acetabulum of the pelvis to form the hip joint. It is composed of a head, a neck, and two bony processes - the greater and lesser trochanters, connected by two ridges, the intertrochanteric line anteriorly and the trochanteric crest posteriorly.
The shaft of the femur descends in a slight medial direction, thus bringing the knees closer to the body's center of gravity, increasing stability. At its middle section, the shaft can be viewed as circular when cross-sectioned, though anteriorly and posteriorly it is flattened. On the posterior surface of the shaft, there are rough ridges of bone referred to as the linea aspera (Latin for ‘rough line’), which splits into the medial and lateral supracondylar lines distally.
The femur is the largest and strongest bone in the body. It is a long bone of the thigh and has a proximal aspect composed of the head, neck, and greater and lesser trochanters, and a shaft. These various parts of the femur provide attachment points for many muscles in the gluteal region, such as gluteus medius, gluteus minimus, and piriformis, and the origin of vastus lateralis.
The lesser trochanter is smaller than the greater trochanter and projects from the posteromedial side of the femur, just inferior to the neck-shaft junction. This is also the site of attachment for iliopsoas. Additionally, the femur shaft is cylindrical in shape and is covered in muscles, with the flat popliteal surface lying between them.
Proximally, the medial border of the linea aspera becomes the pectineal line, while the lateral border becomes the gluteal tuberosity where gluteus maximus attaches. Distally, the linea aspera widens and forms the floor of the popliteal fossa, with the medial and lateral borders forming the medial and lateral supracondylar lines. The distal end of the femur is characterized by the presence of the medial and lateral condyles, which articulate with the tibia and patella to form the knee joint.
The medial and lateral condyles are rounded areas at the end of the femur. The posterior and inferior surfaces articulate with the tibia and menisci of the knee, while the anterior surface articulates with the patella. The more prominent lateral condyle helps prevent the natural lateral movement of the patella; a flatter condyle is more likely to result in patellar dislocation. Additionally, medial and lateral epicondyles, which are bony elevations on the non-articular areas of the condyles, are present. The medial epicondyle is the larger.
The intercondylar fossa, a deep notch on the posterior surface of the femur between the two condyles, contains two facets for attachment of intracapsular knee ligaments. The anterior cruciate ligament (ACL) attaches to the medial aspect of the lateral condyle and the posterior cruciate ligament (PCL) to the lateral aspect of the medial condyle.
The intertrochanteric line and intertrochanteric crest are two ridges of bone on the anterior and posterior surface of the femur, respectively, spanning between the two trochanters. The intertrochanteric line serves as the site of attachment for the iliofemoral ligament (the strongest ligament of the hip joint) and also serves as the anterior attachment of the hip joint capsule. The intertrochanteric crest has a rounded tubercle on its superior half called the quadrate tubercle, to which quadratus femoris attaches.
The femur shaft descends in a slight medial direction; its cross section in the middle is circular but flattened posteriorly at the proximal and distal aspects. On the posterior surface of the femoral shaft, there are roughened ridges of bone, called the linea aspera (Latin for rough line). This splits distally to form the medial and lateral supracondylar lines.
The medial supracondylar line ends at the adductor tubercle, where adductor magnus attaches. These and the other components of the femur are essential for their supportive roles in the flexibility and movement of the body.
On the anterior surface of the femur, there is a structure known as the gluteal tuberosity. This structure is located at the proximal end, which is the end closest to the torso, as well as the part that is connected to the hip joint. The distal end is the part that is furthest away from the torso. At this end is where medial and lateral condyles, medial and lateral epicondyles, and an intercondylar fossa can be found.
The gluteal tuberosity is a bony protrusion which is located on the anterior side at the femur's proximal end. It is important because it is a site of attachment for the gluteal muscles, specifically the gluteus maximus. It is also a prominent landmark for palpation and may be useful for locating the greater trochanter, which is the large protruding bony prominance located on the lateral aspect of the femur.
The medial and lateral condyles are located at the distal end of the femur. The medial condyle is slightly larger than the lateral one and extends farther medially. These structures, along with the medial and lateral epicondyles create the articulating surface of the knee joint. The medial and lateral epicondyles, which are located above the condyles, are also sites of attachment for various muscles that aid in the movement of the knee.
In between the lateral and medial condyles lies the intercondylar fossa. This is a depression located within the two condyles that provides space for the cruciate ligaments, which connect the femur and tibia. Without these ligaments, the knee joint would not have stability and could not move freely.
The distal end of the femur is a complex area because of the number of structures that can be found there. Together, these features help to provide important sites of attachment and stability for the knee joint. Knowing the anatomy of the anterior surface can help medical and health professionals to understand how the knee works and to evaluate any structural problems that may be present.
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