Patella

You have a bone in your knee. It is called a kneecap.

This bone is shaped like a small dish. It is shaped like a triangle, too. It protects your knee joint. Many animals have this bone. Cats, dogs, and birds all have one.

Babies are born with a soft kneecap. It turns into hard bone as they grow. This bone helps you straighten your leg. It is a very important part of your body.

The patella is your kneecap. It is a flat, triangular bone. It sits in front of your knee joint. This bone protects the joint. It also helps you move your leg.

The patella is a sesamoid bone. This means it is a bone inside a tendon. A tendon is a strong cord of tissue. In humans, it is the largest sesamoid bone. Babies are born with a soft kneecap made of cartilage. This cartilage turns into hard bone by age four.

The kneecap helps you straighten your leg. It works with the quadriceps muscle. This is a large muscle in your thigh. The kneecap gives the muscle more power. It acts like a lever to help the leg move.

Sometimes the kneecap can move out of place. This is called a dislocation. It can cause a lot of pain. The bone can also break if you hit it hard. Some people have a bipartite patella. This means the bone is in two parts. This happens when a second layer of bone grows. It mostly happens to men.

The patella is the bone we call the kneecap. It is a flat and rounded triangular bone. This bone sits right in front of your knee joint. Its main job is to protect the front of the knee. It also helps your leg move in a very special way. The patella is a sesamoid bone. This means the bone is tucked inside a muscle or a tendon. In humans, it is the largest sesamoid bone in the whole body.

This bone works like a lever to help you move. It is attached to the quadriceps muscle in your thigh. When that muscle pulls, the patella helps straighten your leg. This process is called knee extension. The bone increases the leverage that the muscle can use. This makes it easier for the muscle to act on the thigh bone. The patella is held in place by several muscles and strong fibers. These help keep the bone stable when you exercise or move.

Every person's kneecap starts out differently when they are very small. Babies are not born with hard bone in their knees. Instead, they have a soft material called cartilage. This cartilage begins to turn into hard bone around age four. This change is called ossification. Sometimes, the bone forms in two different centers that join together. In some people, the bone stays in two parts. This is called a bipartite patella. This type of bone structure happens almost only in men.

There are many different kinds of kneecaps in the world. Many animals have them, like cats, dogs, birds, and mice. However, whales and most reptiles do not have a patella. Some frogs might have a soft version made of cartilage. Scientists think the kneecap may have appeared 350 million years ago. This was when the first tetrapods, or four-legged animals, first appeared. The word patella comes from a Latin word. It means a shallow dish, which describes its shape.

Because the kneecap is right on the outside, it can get hurt. A hard hit can cause a fracture, which is a break. This often leads to swelling and pain. Sometimes the bone can slide out of its proper place. This is called a dislocation and can be very painful. Doctors can sometimes fix this with surgery. One way is to use a tendon from the leg to make a new ligament. This helps the bone stay on the right path.

The patella, commonly known as the kneecap, is a vital part of the human skeletal system. It is a flat, rounded, and triangular bone located at the front of the knee joint. Its primary purpose is to protect the anterior articular surface, which is the front part of the joint. In humans, the patella is categorized as a sesamoid bone. A sesamoid bone is a bone that is embedded within a tendon or a muscle. The patella is the largest sesamoid bone found in the human body.

To understand how the patella works, we must look at its role in knee extension, which is the process of straightening the leg. The patella is attached to the quadriceps femoris muscle via a large tendon. When this muscle contracts, it pulls on the patella to move the lower leg. The bone acts as a lever by increasing the angle at which the quadriceps tendon acts on the femur, or thigh bone. This increased leverage makes the movement much more efficient. To keep the bone in place, the body uses several stabilizers. These include the vastus medialis muscle and the retinacular fibers.

The physical structure of the patella is quite complex. The apex is the lowest, pointed part of the bone, and it provides an attachment point for the patellar ligament. The top of the bone is attached to the quadriceps femoris tendon. The sides of the bone, known as the medial and lateral borders, connect to different parts of the muscle. The back of the bone is divided into two main sections. The upper three-quarters of this posterior surface articulate with the femur. This area is split into a medial and a lateral facet by a vertical ledge. The lower part of the back surface contains the infrapatellar fat pad, which is filled with fatty tissue.

Because the patella experiences significant stress during knee movement, its protective coating is very specialized. This coating is called articular cartilage. In an adult, the articular surface is covered by this cartilage to allow for smooth movement. The cartilage can reach its maximum thickness in the center around age 30. This thickness is necessary because of the intense pressure placed on the patellofemoral joint during resisted knee flexion. Flexion is the act of bending the knee. This specialized structure helps the joint withstand the heavy loads placed on it during physical activity.

Human development of the patella begins long before birth. Babies are born with a patella made of soft cartilage rather than hard bone. The process of turning this cartilage into bone is called ossification. This process typically begins when an ossification center develops between the ages of three and six years. The patella actually starts from two separate ossification centers that eventually unite to form one bone. Sometimes, the bone does not fuse perfectly. This can result in a bipartite patella, where the bone is split into two distinct parts. This variation occurs almost exclusively in men.

Injuries to the patella are common because of its exposed position. A direct impact can cause a fracture, which is a break in the bone. This often leads to swelling and a condition called hemarthrosis, where blood enters the joint. Another common issue is patellar dislocation. This happens when the kneecap slides out of its proper position, usually toward the outside of the leg. This can cause intense pain and swelling. Doctors may use surgery to treat chronic instability. One method is MPFL reconstruction, where a surgeon uses a hamstring tendon to create a new ligament.

Looking beyond humans, the patella is a feature found in many different types of animals. It is present in many tetrapods, which are four-limbed vertebrates, including cats, dogs, birds, and mice. However, it is not found in whales or most reptiles. Interestingly, scientists discovered in 2017 that some frog species have a cartilaginous structure that may function like a kneecap. This discovery suggests that the patella might have first appeared roughly 350 million years ago. The name itself has a historical connection to language. The word comes from a 17th-century Latin term meaning a shallow dish, describing the bone's shape.