Overview
This lecture explains the structure and primary function of the kneecap (patella), emphasizing its biomechanical role in increasing the strength and efficiency of the quadriceps muscle.
Patella Structure & Anatomy
- The kneecap is called the patella, meaning "little dish," located on the front of the knee.
- The patella has an apex (pointing downward) and a base (top portion).
- The patella sits within the quadriceps tendon, above the shin bone's bump (tibial tuberosity).
- In a straightened leg, the patella is not directly over the knee joint anatomy.
- The patella slides up when the leg is extended and down when the knee is bent.
Patella Function & Biomechanical Advantage
- The patella is a sesamoid bone, meaning it develops inside a tendon.
- Sesamoid bones reduce friction and protect tendons from stress and wear.
- The primary function of the patella is to increase the leverage (mechanical advantage) of the quadriceps muscle by extending the lever arm.
- The quadriceps (four muscles: vastus lateralis, vastus medialis, rectus femoris, vastus intermedius) converge into the quadriceps tendon, which passes over the patella and attaches to the tibia.
- The presence of the patella makes the quadriceps up to 30% stronger by increasing the lever arm.
- The mechanical advantage is greatest when the knee is flexed between 20° to 60°.
Misconceptions About Patella Function
- While the patella offers some protection to the knee joint, this is not its main function.
- Babies do not have a fully formed bony patella during crawling, so its protective role is limited in early life.
Key Terms & Definitions
- Patella — the kneecap; a small bone on the front of the knee embedded in the quadriceps tendon.
- Sesamoid Bone — a bone formed within a tendon, reducing friction and improving leverage.
- Quadriceps Tendon — tendon where the four quadriceps muscles converge and attach to the patella.
- Patellar Ligament — connective tissue extending from the patella to the tibial tuberosity.
- Mechanical Advantage — increased force or efficiency gained through anatomical structures like the patella.
Action Items / Next Steps
- Review the biomechanics of levers and pulleys as they apply to muscle function.
- Learn the names and locations of the quadriceps muscles.
- Study the flexion and extension mechanics of the knee joint for further understanding.