Leg · Sesamoid bone
Patella (Kneecap)
The patella, or kneecap, is the small bone at the front of the knee. It sits within the thigh-muscle tendon and protects the knee joint while improving the power of the muscles that straighten the leg.
What it is
The patella is the largest sesamoid bone — a bone embedded within a tendon. It lies at the front of the knee inside the tendon of the quadriceps muscle.
Where it is
At the front of the knee, gliding in a groove at the lower end of the femur as the knee bends and straightens.
What it does
Protects the front of the knee joint and acts like a pulley, increasing the leverage of the quadriceps muscle so it can straighten the knee more powerfully.
Connections
Joints and connections
- Patellofemoral joint (with the femur)
When things go wrong
Common injuries and conditions
- Patella fracture (from a direct blow or fall)
- Patellar dislocation
- Anterior knee pain / patellofemoral pain syndrome
Education and reference only. This explains the anatomy in plain terms; it is not a diagnosis. A severe injury, a visibly deformed limb, or the inability to move or bear weight needs urgent assessment — call 999 or go to A&E for a serious injury.
Did you know?
An interesting fact
The patella is the largest sesamoid bone in the human body.
Answers
Patella: frequently asked questions
What is the kneecap for?
The kneecap (patella) protects the front of the knee and works as a pulley, boosting the power of the thigh muscle that straightens the leg.
Can you walk without a kneecap?
It is possible to walk after a kneecap is removed or badly injured, but the knee is weaker at straightening. Kneecap injuries are assessed and managed by a clinician.
Explore the leg
Related bones
Sources
Where this is drawn from
- NHS — Anatomy and body systems
- Gray's Anatomy for Students (Drake, Vogl, Mitchell)
- TeachMeAnatomy — skeletal system
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