Your knees are some of the hardest-working joints in your body. They help you stand, walk, run, and change direction—and they absorb a tremendous amount of force every day. Here are a few interesting facts about the knees and why keeping them healthy matters.

Fact 1: Knees are the most complex joint in the body.

While your knees might look like a simple joint where your kneecap sits between your upper and lower leg, they are actually a complex system. The joint connects your femur (thigh bone), patella (kneecap), and tibia (shin bone), all held together by a network of tendons, ligaments—such as the ACL and MCL—and cushioning cartilage.

Fact 2: Ostriches have 4 kneecaps, 2 per leg.

This unique anatomy is believed to help them run at high speeds—up to miles per hour—by aiding faster knee extension and providing extra protection for the tendon. Smooth cartilage covers the ends of the bones in the knee, helping them glide against each other as they reach high speeds.

Fact 3: Everyone has unique kneecaps.

Just like your fingerprints and retinas, everyone’s kneecap shape is completely unique. The shape, bone density, and articular surface patterns of kneecaps vary highly between people, making them distinct.

Fact 4: Healthy knees do not have direct bone contact.

The knee is often called a “floating joint” because it is a synovial joint, meaning it isn’t directly connected to neighboring bones by bone itself—it relies on muscles, ligaments, and fluid.

Fact 5: Babies are born without fully formed kneecaps.

Babies are born without fully formed bony kneecaps, having only soft cartilage instead, which allows for extreme flexibility. This cartilage, which acts as a scaffold for future growth, does not begin to fully harden (ossify) into solid bone until around age two to six, with the process finishing around age ten to twelve.

The takeaway
Your knees play a key role in nearly every movement you make. Staying active, strengthening the muscles around the joint, and addressing pain early can help protect your knees and keep you moving with confidence.