Knee anatomy is about the structure of the knee – that is, the parts that makeup the knee. This article also tells you how a normal knee works and provides resources for problems of the knee joint or it’s parts including knee injuries.
Our knee is the most complicated and largest joint in our body. It’s also the most vulnerable because it bears enormous weight and pressure loads while providing flexible movement. When we walk, our knees support 1.5 times our body weight; climbing stairs is about 3-4 times our body weight and squatting about 8 times.
The knee joint is a synovial joint which connects the femur, our thigh bone and longest bone in the body, to the tibia, our shinbone and second longest bone. There are two joints in the knee—the tibiofemoral joint, which joins the tibia to the femur and the patellofemoral joint which joins the kneecap to the femur. These two joints work together to form a modified hinge joint that allows the knee to bend and straighten, but also to rotate slightly and from side to side.
The knee is part of a chain that includes the pelvis, hip, and upper leg above, and the lower leg, ankle and foot below. All of these work together and depend on each other for function and movement.
The knee joint bears most of the weight of the body. When we’re sitting, the tibia and femur barely touch; standing they lock together to form a stable unit. Let’s look at a normal knee joint to understand how the parts (anatomy) work together (function) and how knee problems can occur.
Anatomical terms
Anatomical terms allow us to describe the body clearly and precisely using planes, areas and lines. Instead of your doctor saying “his knee hurts” she can say “his knee hurts in the anterolateral region” and another doctor will know exactly what is meant. Below are some anatomic terms surgeons use as these terms apply to the knee:
- Anterior — if facing the knee, this is the front of the knee
- Posterior — if facing the knee, this is the back of the knee, also used to describe the back of the kneecap, that is the side of the kneecap that is next to the femur
- Medial — the side of the knee that is closest to the other knee, if you put your knees together, the medial side of each knee would touch
- Lateral — the side of the knee that is farthest from the other knee (opposite of the medial side)
Structures often have their anatomical reference as part of their name, such as the medial meniscus or anterior cruciate ligament. The medial meniscus would refer to the meniscus on the inside of the knee, the anterior crucial ligament would be on the anterior side (front) of the knee.
Structures of the Knee
The main parts of the knee joint are bones, ligaments, tendons, cartilages and a joint capsule, all of which are made of collagen. Collagen is a fibrous tissue present throughout our body. As we age, collagen breaks down.
The adult skeleton is mainly made of bone and a little cartilage in places. Bone and cartilage are both connective tissues, with specialized cells called chondrocytes embedded in a gel-like matrix of collagen and elastin fibers. Cartilage can be hyaline, fibrocartilage and elastic and differ based on the proportions of collagen and elastin. Cartilage is a stiff but flexible tissue that is good with weight bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair. It is the high water content that makes cartilage flexible.
