The Patella

The Patella is the largest sesamoid bone in the

body

PatellaPatella

A sesamoid bone is a bone that is

embedded in the tendon of a muscle

Anterior view, right knee

PatellaPatella

The Patella lies in the tendon of the

Quadriceps muscle

QuadricepQuadricepss

Patellar Patellar TendonTendon

Anterior view, right knee

The Patella has a wide upper border

Wide upper Wide upper borderborder The lower border is pointed

and is called the Patellar Apex

Patellar ApexPatellar Apex

The Patella has a wide upper border

The ventral surface is convex and ridged

Ventral Ventral surfacesurface

The posterior surface has articular facets that articulate

with the Distal Femur

The Posterior Surface

The Posterior Surface

The upper 2/3rds is smoothand covered in hyaline cartilage

The Posterior Surface

The upper 2/3rds is smoothand covered in hyaline cartilage

It engages with theMedial and Lateral Femoral Condyles

Patella

Quadriceps Muscle

Patellar TendonThe patella engages with the

Medial and Lateral Femoral Condyles

The Posterior Surface

There is a prominent vertical ridge that

divides the posterior articular

surface into medial and lateral facets

The Posterior Surface

The Lateral Facet is larger and gently concave

The Posterior Surface

The Lateral Facet is larger and gently concave Medial Facet

The Posterior Surface

The inferior aspect of the posterior surface is

roughened due, partly, to the attachment of the

patellar tendon

Medial Facet

Patellar Stability

upwards and upwards and outwardsoutwards

The Patella is embedded in the Tendon of the

Quadriceps

upwards and upwards and outwardsoutwards

On contraction, the Quadriceps pulls the Patella upwards and outwards

upwards and upwards and outwardsoutwards

This is counteracted by the action of Vastus Medialis which pulls the Patella inwards

On contraction, the Quadriceps pulls the Patella upwards and outwards

The Patella is embedded in the Tendon of the

Quadriceps

The Lateral Femoral Condyle projects further forward than the Medial Femoral

Condyle and this provides a bony obstacle to lateral movement of the Patella

Lateral Femoral Lateral Femoral CondyleCondyle