Though they are small, almost everything you do with your legs requires your knees. Their hinging action allows your legs to bend and straighten, which you need for standing, walking, crouching, jumping, and turning. You might know how often you use them, but here are seven fascinating facts about your knees that might surprise you.

1. Babies are born without kneecaps.

Babies’ kneecaps are made up of soft cartilage that hasn’t yet ossified into bones, so their “true” kneecaps don’t show up on x-rays until somewhere between two and six years of age.

2. The knee connects two bones.

Like the old song goes, the knee bone is actually connected to the thighbone, so to speak. More accurately, the knee is the joint where the femur bone of your thigh and the tibia bone of your shin meet, allowing flexion. The knee joint allows your leg to kick and jump, run and leap.

3. You can walk without a kneecap.

Your kneecap, known as the patella, is a small bone that protects your knee joint. If you are so unlucky as to shatter or break your kneecap badly enough, it will most likely have to be surgically removed. In those cases, though, surgeons do not create or install kneecap prostheses—because you can walk without a kneecap. Kneeling, however, may be a challenge without one, requiring protective gear.

4. For such a small part of the body, it’s prone to many problems.

For such a tiny part of the body, the knee is prone to a large variety of aches, pains, and injuries. Even small repetitive strains can cause serious ligament and tendon injuries, such as tearing of the meniscus or chronic inflammation. The autoimmune condition rheumatoid arthritis, and a collagen disorder known as Ehlers-Danlos, both tend to cause tremendous pain in the knee joint.

5. Knees are a favorite of terrorists and crime groups.

Kneecapping is a nasty torture practice used by terrorists and organized crime groups to destroy the kneecaps, either by shooting a knee, or shattering them with a blunt object. The result is not life-threatening, but it's extremely painful and permanently disabling.

6. Knees are associated with surrender.

The phrase “brought to one's knees” suggests a position of submission or desperation; to be “cut off at the knees" usually connotes humiliation or surrender. In ancient Greece, the phrase "on the knees of the gods" (theón en gounasi) meant something was beyond human control or knowledge.

7. Shel Silverstein wrote a poem about knees.

The narrator of the kids’ poem “Stop, Thief!” by famous poet Shel Silverstein imagines someone stealing their knees, and asks a policeman for assistance since “my feet and legs just won’t connect.” Guess they hadn’t had their kneecaps removed!