Patella Fractures: Approach to Treatment

Damayea I. Hargett, MD; Brent R. Sanderson, DO; Milton T.M. Little, MD


J Am Acad Orthop Surg. 2021;29(6):244-253. 

In This Article


As the largest sesamoid bone in the body, the patella's primary ossification typically occurs by the age of 5 or 6 years. The patella forms from a single ossification center in 97% to 98% of patients, whereas in 2% to 3% of the cohort, it develops as a bipartite patella. This usually occurs when the secondary ossific nucleus fails to unite with the primary nucleus. The superolateral aspect of the patella is the most common site of the secondary nucleus.

The patella is located anterior to the knee joint with musculotendinous insertions of the quadriceps tendon and tensor fascia lata into the anterosuperior margin. The patellar ligament arises from the inferior pole attaching to the tibial tubercle. The lateral and medial retinacula are formed by the quadriceps aponeurosis, vastus lateralis, iliotibial band, and vastus medialis, respectively. Posteriorly, the articulating surface is composed of a medial facet and larger lateral facet, separated by a median vertical ridge. The medial facet contains a far medial portion known as the odd facet, which is in contact with the femoral condyle in full flexion. The thickest articular cartilage in the body covers this patellar articular surface. The ligamentous and tendinous insertions maintain the patellar articulation within the femoral trochlea while enhancing the biomechanical advantage of the knee extensor mechanism.[1]

The vascular supply to the patella is primarily derived from an extraosseous and intraosseous blood supply arising from an anastomotic ring from the genicular and anterior tibial recurrent arteries and midpatellar vessels. Lazaro et al[2] demonstrated that the inferomedial vessels were the most dominant vessel in 80% of cadavers in their vascular evaluation of the patellar blood supply.