The structure indicated is the medial condyle of the femur.

The distal end of the femur forms two rounded condyles which articulate with the tibia below and the patella anteriorly – the medial condyle and the lateral condyle.

The linea aspera is a roughened crest of bone on the posterior aspect of the femur. Distally the linea aspera forms two ridges known as the lateral supracondylar line and the medial supracondylar line which as the name suggests, terminate just superiorly to the lateral and medial femoral condyles respectively. At the end of the medial supracondylar line is a tubercle called the adductor tubercle.

In between the medial and lateral femoral condyles is the intercondylar fossa. On each condyle is a smaller epicondyle which serve as the point of attachment for the collateral ligaments – the medial collateral (MCL) and the lateral collateral ligaments (LCL).

Learn more about the femur in this anatomy tutorial.