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Recommended video: Knee joint [29:49]
Sagittal view of the knee joint showing the patellofemoral and tibiofemoral joints.
Patella (ventral view)

The patella is also known as the kneecap. It sits in front of the knee joint and protects the joint from damage.

It is the largest sesamoid bone in the body, and lies within the quadriceps tendon. The kneecap is an example of a bone we are all familiar with, and which has a significant functional role.

In this article we will discuss the anatomy and clinical relevance of the patella.

Key facts about the patella
Type Sesamoid bone
Location Within the quadriceps tendon, anterior to the knee joint
Parts Apex (pointing inferiorly), medial and lateral borders, base (lies proximally)
Function Aids with knee extension, allows for smooth movement during knee flexion/extension, protects the anterior surface of the knee joint
Blood supply Superior lateral and medial, inferior lateral and medial, descending and anterior genicular arteries
  1. Anatomy
  2. Function
  3. Blood supply
  4. Patellofemoral joint
  5. Clinical points
    1. Sinding-Larsson Johansson syndrome
    2. Patellar reflex
    3. Patellar dislocation
    4. Patellar fracture
  6. Sources
+ Show all


The patella is the largest sesamoid bone in the body and it lies within the quadriceps tendon in front of the knee joint. The bone originates from multiple ossification centres that develop from the ages of three to six, which rapidly coalesce. The patella is a thick, flat, triangular bone with its apex pointing downwards. The bone has a medial and lateral border, as well as its base which lies proximally.

The patella is a dense trabecular bone with a thin compact lamina covering it. The attachment of the quadriceps muscle if found on the superior surface extends distally onto the anterior surface. The rough marking found at the lateral and medial borders of the patella represent the attachments of vasti lateralis and medialis, and those at the apex represent the attachment of the patellar ligament.

The apex of the patella gives rise to the patellar ligament, which inserts onto the tibial tuberosity on the anterior surface of the tibia. The middle third of the patella has various vascular openings that allow for arteries to penetrate and supply the bone.

The patella is stabilized by the horizontal fibers of vastus medialis, as well as the anterior projection of the lateral femoral condyle. The tension in the medial patellar retinaculum also helps in its stability.

For more details about the anatomy of the patella, take a look below:


The primary function of the patella is during knee extension. The fact that the patella sits atop the anterior surface of the femoral condyles, increases the angle at which the quadriceps tendon pulls on the shaft of the tibia. The patella also functions to allow for smooth movement of the knee in flexion and extension, and also protects the anterior surface of the knee joint.

The patella is only one bone of the human body! Simplify your learning of the remaining 205 using Kenhub's skeletal system quizzes!

Blood supply

The blood supply to the patella arises from the genicular arteries, branches of the popliteal artery. There is:

  • a superior lateral and medial
  • inferior lateral and medial
  • a descending and anterior genicular artery

They form a peripatellar anastomosis and supply the patella and the knee joint.

Patellofemoral joint

The superior two thirds of the posterior articular surface of patella articulates with the anterior surface of the femoral condyles to form the patellofemoral joint. The lateral articulating surface of the patella is usually larger than the medial articulating surface. However the medial femoral condyle is larger and projects further anteriorly than the lateral femoral condyle.

Patella: want to learn more about it?

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