The femur is the large bone between the knee and hip joints. Its size and strength make it a very important base for soft tissue attachment, weight bearing, and bio-mechanical purposes. The femur is a long bone, which means it has a hard outer surface known as compact bone, with a mesh-like interior called cancellous bone, designed to take pressure from multiple angles.
It is also useful to note that the cancellous bone contains bone marrow. The femur helps to make up two joints distally, articulating with the tibia and the patella, creating the tibiofemoral and patellofemoral joints respectively. Superiorly, the femur slips into the acetabulum of the hip, creating the acetabulofemoral joint.
Proximal end - head, neck, greater trochanter, lesser trochanter, intertrochanteric crest
Shaft - Borders: lateral and medial; Surfaces: anterior, medial, lateral; Ridges: lateral ridge (gluteal tuberosity), pectineal line, spiral line (these three lines converge and form the linea aspera)
Distal end - lateral and medial condyles, intercondylar fossa, lateral and medial epicondyles
|Origins||Gastrocnemius, vastus lateralis, vastus medialis, vastus intermedius muscles|
|Insertions||Gluteus maximus, gluteus medius, gluteus minimus, iliopsoas, lateral rotator group, adductors of the hip|
Hip: femoral head with the acetabulum of the pelvis
Knee: lateral and medial condyles of the femur with the tibial plateaus of the tibia (tibiofemoral); Patellar surface of the femur with the posterior surface of the patella (patellofemoral)
|Clinical relations||Coxa vara and coxa valga, genu vara and genu valgum; fractures (dangerous because of the dissection of the femoral artery); benign and malignant tumors (sarcomas)|
This article will discuss all of the important anatomical landmarks and clinical aspects related to the femur.
At its most superior point, the femur contains the femoral head, which articulates with the acetabulum. The head of the femur is very like half a sphere, allowing for a smooth circumduction motion at its joint.
The acetabulofemoral joint is stable due to the bony contact, which sees the acetabulum accommodate 4/5ths of the femoral head. Although the articulation is smooth, this smoothness is interrupted by a small fovea, for the ligamentum teres femoris to insert into.
Supporting the head is the femoral neck, which is covered until the base by the fibrous capsule and its ligaments.
Looking inferiorly, the greater and lesser trochanters and intertrochanteric line are important attachment sites for soft tissue.
- The greater trochanter is a large palpable emergence that is an insertion point for gluteus medius, gluteus minimus, piriformis, obturator internus, superior gemellus, inferior gemellus and obturator externus muscles.
- The lesser trochanter is found on the posteromedial side of the femoral neck. This projection is the attachment site for illiopsoas and superior portions of the adductor magnus muscles.
- On the posterior surface of the femur, the greater trochanter is connected somewhat to the lesser trochanter by the inferomedially running intertrochanteric crest. It is the site of insertion for the quadratus femoris muscle.
- On the anterior surface of the femoral neck, running between the greater and lesser trochanters is the intertrochanteric line. At its superior limit, it provides attachment to the iliofemoral ligament.
As the head and neck transcends into the shaft of the femur, there are three descending elongated ridges, all of which merge to form the linea aspera.
- The more lateral ridge is called the gluteal tuberosity (or gluteal line), which provides an attachment site for the deep, distal fibres of the gluteus maximus muscle. It extends from the base of the greater trochanter to the lateral lip of the linea aspera.
- Medial to this, is the pectineal line, a site of attachment for the pectineus muscle. This is a relatively short, curved ridge which extends from the base of the lesser trochanter.
- Immediately adjacent to, and often confused with the pectineal line, is the spiral line. It is a continuation of the intertrochanteric line (found anteriorly), which wraps around the proximal shaft of the femur to terminate on the medial lip of the linea aspera. The spiral line is the origin of the vastus medialis muscle.
The shaft of the femur is thinnest in the middle, progressively getting bigger as it reaches both ends of the bone. The shaft has less in terms of bony landmarks, only really the posterolateral rough line of the linea aspera. The linea aspera provides attachment to several attachment points of the thigh, for example the adductor longus, short head of biceps femoris muscle and vastus medialis muscle.
Concerning the distal end, the immediately obvious landmarks are the two condyles on either side of the patellar surface and intercondylar fossa. Just superior to the condyles is an area called the medial and lateral epicondyles (epi = above/upon), that are an origin to both collateral ligaments which prevent excessive abduction and adduction of the knee.
The lateral condyle articulates with the articular surface of the tibia, and is the larger of the two condyles. The medial condyle is more convex than its counterpart, and is easier to palpate. Both condyles are attachment points to two very important soft tissue structures of the knee that enables function, and are very difficult to recover from when injured.
The first is the knee menisci, which are two semi-lunar shaped pads of fibrocartilage that are attached to the opposing articular bone surfaces that forms the tibiofemoral joint. The menisci allows for a smooth movement of the knee. The menisci is stapled down to the femoral condyles via the meniscofemoral ligaments that attach to the posterior horn of the lateral meniscus to the medial femoral condyle. Studies suggest that these ligaments act to support the posterior cruciate ligament against posterior forces on the tibia when the femur is fixed.
The second important soft tissue structures are the two cruciate (meaning ‘crossed’) ligaments. The anterior cruciate ligament is thinner and more likely to get damaged, as it prevents a more likely movement - tibial anteriorization of the fixed femur and hyper-extension of the knee. The posterior cruciate ligament has the opposite effect, preventing tibial posteriorization of the fixed femur and hyper-flexion of the knee.
A lot of the mechanical ability to walk upright effectively derives from the relationship between the femur and acetabulum. A key component in this the angle of inclination (or the neck-shaft angle).
The angle of inclination is the angle of the femoral neck in relation to the shaft of the femur. This is important because it brings the femur away from the body, enabling a swinging movement, thus allowing a walking technique that is more fluid and expends less energy. This is visible when looking closely at someone’s walking pattern, it may be obvious to see that the pelvis swings around during the gait cycle.
If the angle of inclination is abnormal (normal is usually 90-130 degrees depending on gender) it can affect the forces generated through the hip joint and the effectiveness of the hip abductor muscles.
The Q-angle is the angle between the rectus femoris muscle and the patellar tendon alignment. Because the rectus femoris is inclined to pull medially (due to the oblique fibres of vastus medialis) but the patellar ligament is directed laterally (due to the strength of the lateral vastus muscles), any imbalance may cause weakness in the knee. The female pelvis is wider to support childbirth, whereas the male pelvis is narrower but deeper. The pubic arches are also different, with the female pubic arch obtuse compared to the male pubic arch angle usually being acute.
Because the hip joint is constantly under pressure and resisting gravity’s downward push, problems in this area can become quite potent. Coxa vara and coxa valga are terms to describe the decreased and increased position of the head and neck in relation to the shaft of the femur respectively. The diagnosis of coxa vara and coxa valga comes in two categories; congenital and acquired. Congenital problems are considered to be due to issues with the child before birth while acquired problems are problems that have developed over time, maybe because of poor posture or the body’s compensatory mechanics due to an injury. Coxa valga is associated with genu vara (bow legged syndrome) while coxa vara is associated with genu valgum (knock-kneed syndrome).