The patella, or kneecap, is a sesamoid bone located at the front of the knee joint, within the patellofemoral groove of the femur. It is the largest sesamoid bone located within the quadriceps tendon, and its superior aspect is attached to the quadriceps tendon while its inferior aspect is connected to the patellar ligament. In this article we will look at the anatomy of the patella – its surface features, functions and clinical relevance.
The patella is triangular in shape, with anterior and posterior surfaces. The apex of the patella is situated inferiorly and is connected to the tibial tuberosity by the patellar ligament. The base forms the superior aspect of the bone and provides the attachment area for the quadriceps tendon.
The posterior surface of the patella articulates with the femur and is marked by two distinct facets: a medial facet which articulates with the medial condyle of the femur and a lateral facet which articulates with the lateral condyle of the femur.
The patella has two primary functions. Firstly, its presence in the knee joint enhances the leverage that the quadriceps tendon can exert on the femur, thereby increasing the efficiency of the muscle. Secondly, it serves as a protective structure that shields the anterior aspect of the knee joint from physical trauma.
Patellar dislocation describes a condition in which the patella is displaced out of its normal position in the patellofemoral groove. It accounts for around 3% of all knee injuries and most commonly occurs as a result of a forceful impact to the patella or sudden forceful twisting of the knee. This condition is especially common in individuals participating in sports such as football, rugby and ice hockey.
A patellar fracture is a break in the patella bone, usually caused by direct trauma or sudden contraction of the quadriceps muscle. This condition is more frequently observed in males, and is most commonly seen in individuals between the ages of 20 and 50. In cases where the patellar breaks into multiple fragments, the proximal fragment will usually be displaced superiorly by the quadriceps tendon, while the distal fragment is pulled inferiorly by the patellar ligament.
