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The Femur & Patella | Thigh Bone & Kneecap | Runner's Knee

Author C. Sanders. Published on June 17, 2011 - 10:41 am (10605 views — 700 words)

The femur, or thigh bone, is the longest, heaviest, and strongest bone in the body. Its proximal end articulates with the acetabulum of the hip bone. Its distal end articulates with the tibia and patella. The body (shaft) of the femur angles medially and, as a result, the knee joints are closer to the midline. The angle (angle of convergence) is greater in females because the pelvis is broader.

The proximal end of the femur consists of a rounded head that articulates with the acetabulum of the hip bone to form the hip (coxal) joint. The head contains a small centered depression (pit) called the fovea capitis. The ligament of the head of the femur connects the fovea capitis of the femur to the acetabulum of the hip bone.

The neck of the femur is a constricted region distal to the head. A "broken hip" is more often associated with a fracture in the neck of the femur than fractures of the hip bones. The greater trochanter and lesser trochanter are projections from the junction of the neck and shaft that serve as points of attachment for the tendons of some of the thigh and buttock muscles.

The greater trochanter is the prominence felt and seen anterior to the hollow on the side of the hip. It is a landmark commonly used to locate the site for intramuscular injections into the lateral surface of the thigh. The lesser trochanter is inferior and medial to the greater trochanter. Between the anterior surfaces of the trochanters is a narrow intertrochanteric line. A ridge called the intertrochanteric crest appears between the posterior surfaces of the trochanters.

Inferior to the intertrochanteric crest on the posterior surface of the body of the femur is a vertical ridge called the gluteal tuberosity. It blends into another vertical ridge called the linea aspera. Both ridges serve as attachment points for the tendons of several thigh muscles.

The expanded distal end of the femur includes the medial condyle and the lateral condyle. These articulate with the medial and lateral condyles of the tibia. Superior to the condyles are the medial epicondyle and the lateral epicondyle, to which ligaments of the knee joint attach. A depressed area between the condyles on the posterior surface is called the intercondylar fossa. The patellar surface is located between the condyles on the anterior surface.

The Patella / Kneecap

The patella, or kneecap, is a small, triangular bone located anterior to the knee joint. The broad proximal end of this sesamoid bone, which develops in the tendon of the quadriceps femoris muscle, is called the base; the pointed distal end is referred to as the apex. The posterior surface contains two articular facets, one for the medial condyle of the femur and another for the lateral condyle of the femur. The patellar ligament attaches the patella to the tibial tuberosity. The patellofemoral joint, between the posterior surface of the patella and the patellar surface of the femur, is the intermediate component of the tibiofemoral (knee) joint. The patella increases the leverage of the tendon of the quadriceps femoris muscle, maintains the position of the tendon when the knee is bent (flexed), and protects the knee joint.

Clinical Connection: Patellofemoral Stress Syndrome

Patellofemoral stress syndrome (“runner’s knee”) is one of the most common problems runners experience. During normal flexion and extension of the knee, the patella tracks (glides) superiorly and inferiorly in the groove between the femoral condyles. In patellofemoral stress syndrome, normal tracking does not occur; instead, the patella tracks laterally as well as superiorly and inferiorly, and the increased pressure on the joint causes aching or tenderness around or under the patella. The pain typically occurs after a person has been sitting for a while, especially after exercise. It is worsened by squatting or walking down stairs. One cause of runner’s knee is constantly walking, running, or jogging on the same side of the road. Because roads slope down on the sides, the knee that is closer to the center of the road endures greater mechanical stress because it does not fully extend during a stride. Other predisposing factors include running on hills, running long distances, and an anatomical deformity called knock-knee.