Thanks to COVID-19 handshakes are no more. They have been replaced with the elbow bump. That got me thinking about a question I've been asked many times over the years. I've decided now is as good of a time as any to answer.
So as I mentioned, this all started a long time ago we posted on our Youtube channel explaining why our bodies have and need kneecaps. You can check out that video below if you're interested. But ever since that video was released, I have gotten many questions about why we don't have elbow caps.
One might presume that a hinge joint like the elbow would need a similar structure since the knee is also a hinge.
Without getting in too much detail, we have something that acts as a pivot joint on our ulna (one of the two bones that make up our forearm) called the olecranon. This is the pointy part of our elbow. So instead of having a floating structure like the kneecap, our elbow complex has an attached portion.
So although both the knee and elbow are hinge joints, their functions are entirely different.
So why is this important?
1. We need more stability for our wrists, hands and fingers.
This affords more dexterity and freedom for our shoulder and upper extremity to perform delicate manipulations and function. When the ulna is stable, we can rotate the radius (the other bone in our forearm) better for supination and pronation tasks.
2. We don't use our arms for propulsion or gait.
Unlike our legs, our arms rarely have to support the entirety of our bodyweight. Our arms also don't have to be able to propel our bodies to walk or run which requires massive amounts of force. The kneecap allows for that force to slide easily with minimal friction.
3. Developmentally, kneecaps were fundamental. Elbow caps, not so much.
Before you learn to walk, you must first learn to crawl. Imagine trying to crawl without a kneecap. We would all have to walk like Bambi. Our elbows rarely have to perform that kind of task, so we are able to function without an elbow cap.
So next time you wonder why we have such a hard elbow, you'll know it's because it doesn't have a cap to help it out. Whoever our maker is or the way we evolved made our elbows in such a way to allow for intricate movement. They support our hands which produce some of the greatest art in the world and the ability to perform incredible tasks.