Clinical Anatomy: The Bones of the Knee and Leg
The bones of the knee and the leg include the femur, which is the large thigh bone; the tibia and fibula, which are the leg bones between the knee and ankle; and the patella, which is sometimes called the kneecap.
Femur: This long bone runs between the hip and the knee. The medial and lateral femoral condyles protrude from the distal end of the femur (the medial femoral condyle is close to the midline of the body, and the lateral femoral condyle is farther from the midline). Posteriorly, the indented space between the condyles is called the intercondylar fossa. Anteriorly, the condyles are joined, forming the smooth patellar surface.
The linea aspera is a ridge that runs longitudinally (lengthwise) along the posterior surface of the femur. At its distal end, it diverges into the medial and lateral supracondylar lines that run toward their respective condyles. These lines serve as attachment points for muscles.
Tibia: This long bone is the larger of the two leg bones below the knee. The proximal end has two projections, called the medial and lateral condyles. An intercondylar eminence with two tubercles (bony prominences) lies between the condyles. The articular surfaces between the condyles and eminence are called the medial and lateral tibial plateaus. The tibial tuberosity (another bony outgrowth) projects anteriorly from the shaft.
Medial tibial stress syndrome (MTSS), better known as “shin splints,” is a common condition, especially in people who jog or run frequently. It may be the result of a strained tibialis anterior muscle or feet that pronate too much (in other words, flat feet). Shin splints cause a dull, achy pain in the anterior part of the leg. Treatment for shin splints includes rest, ice on the anterior part of the leg, nonsteroidal anti-inflammatory medications, and arch supports or appropriate shoes.
Fibula: This long bone, the thinner of the two leg bones, is located lateral to the tibia. The proximal part of the fibula has an enlarged head that articulates (forms a joint) with the tibia.
The shafts of the tibia and fibula are connected by an interosseous membrane. It’s a sheet of connective tissue that fills most of the space between the two bones. The membrane has one opening at the top that allows for passage of blood vessels.
Patella: This large sesamoid bone is formed in the tendon of the quadriceps muscle. It’s shaped like a triangle, with a thick base forming the superior (top) border. The pointed apex is at the inferior (bottom) part of the bone. The anterior (front) surface is slightly convex (in other words, the surface curves outward), and the posterior (back) part has medial and lateral articular surfaces (articular surfaces are joint forming).
Patellofemoral syndrome, or chondromalacia patella, is a painful condition in which the cartilage on the articular surfaces of the patella becomes soft and breaks down. The condition occurs when the patella rubs against the femur due to problems with patellar alignment or excessive physical activity involving the knee. Patellofemoral syndrome is most commonly seen in adolescent and young adult females.