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Anatomy Insight |  Comic  Sans | Lexend

The proximal end of the femur consists of the head, neck, and two projections called the greater and lesser trochanters. 

The head is rounded and articulates with the acetabulum of the hip bone to form the hip joint. 

On the head is a small depression called the fovea capitis, which provides attachment for a ligament that connects the femur to the acetabulum and carries an important artery.

Below the head is the neck of the femur, which connects the head to the shaft. This region is narrower and is a common site of fractures. 

The greater trochanter is a large, prominent projection located laterally and serves as an attachment point for several muscles, giving them increased leverage. 

The lesser trochanter is smaller and located on the medial side, serving as the attachment for a powerful muscle. 

The greater and lesser trochanters are connected by the intertrochanteric line on the anterior side and the intertrochanteric crest on the posterior side.

The shaft of the femur is long and slightly curved, being convex in front and concave behind. Along its posterior surface runs a rough ridge called the linea aspera, which serves as an attachment site for many muscles of the thigh and hip. 

Near the upper part of the shaft is the gluteal tuberosity, which continues into the linea aspera.

The distal end of the femur is expanded and forms two large rounded areas called the medial and lateral condyles. These articulate with the tibia to form the knee joint.

Patella

The patella, or kneecap, is the largest sesamoid bone in the body. It is embedded within the tendon of the quadriceps femoris muscle, which crosses the knee joint to attach to the tibia. A sesamoid bone forms within a tendon where it passes over a joint.

The patella articulates with the patellar surface of the femur and helps prevent the tendon from rubbing directly against the bone during movement. It also increases the leverage of the quadriceps muscle by holding the tendon away from the joint, making its action more effective. The patella does not articulate with the tibia.

The proximal end of the tibia is expanded and forms the medial and lateral condyles. These have smooth surfaces that articulate with the condyles of the femur to form the knee joint. 

Between them is the intercondylar eminence, which serves as an attachment point for important ligaments of the knee.

On the anterior surface near the top is the tibial tuberosity, which is the attachment point for the tendon associated with the patella. 

The shaft of the tibia is triangular in shape. Its anterior border runs down the front of the leg and is easily felt, while the lateral side has the interosseous border for attachment of the interosseous membrane that connects the tibia and fibula. On the posterior surface is the soleal line, which provides attachment for muscles.

At the distal end, the tibia expands again. On its medial side is the medial malleolus, which forms the bony prominence on the inner side of the ankle. The distal tibia articulates with the talus of the foot to form part of the ankle joint. On the lateral side is the fibular notch, where the tibia articulates with the fibula.