The knee is one of the most important and hardest-working joints in the body. Whether you're walking, running, jumping, or simply getting up from a chair, your knees are constantly in action. The knee complaints that we commonly see in the clinic are often a result of over use injuries or a result of a problem elsewhere in the leg, as well as after trauma.
In this blog, we will look at the anatomy and how a healthy knee works.
The Knee: A Hinge Joint
Think of your knee as a hinge—just like the one on a door. It mainly moves in two directions: bending (flexion) and straightening (extension). But unlike a simple door hinge, the knee also has a bit of rotation and glide, which helps with movement and balance.
The knee is made up of three major bones:
Thigh bone (Femur) – The big bone in your upper leg.
Shin bone (Tibia) – The large bone in your lower leg.
Kneecap (Patella) – A small, shield-like bone in front of the knee that helps protect it.
These bones fit together to form the knee joint, allowing movement while bearing a lot of weight. There is also a 4th bone known as the fibula that forms a joint with the tibia slightly below the knee itself.
The Software of the Knee: Ligaments, Cartilage and Muscles.
Since the knee takes on a lot of strain, it needs several key structures to stay strong, stable, and move in a controlled manner:
Ligaments
The ligaments are strong, rope-like tissues that hold the knee together and stop it from moving too much in any direction. There are four main ligaments:
The ACL (Anterior Cruciate Ligament) stops the shin bone from sliding forward too much.
The PCL (Posterior Cruciate Ligament) stops the shin bone from moving backward too much.
The MCL (Medial Collateral Ligament) and LCL (Lateral Collateral Ligament) prevent excessive sideways motion.
Cartilage
The cartilage is the smooth, rubbery tissue that cushions the knee joint and prevents the bones from rubbing together. The two main types of cartilage in the knee are:
The meniscus, which is formed of two C-shaped pieces of cartilage (one on each side of the knee) that absorb shock and help distribute weight evenly.
Articular Cartilage which covers the surface of the bones allowing smooth movement.
Muscles
The muscles of the knee provide power, movement and stability for the knee. The 3 key groups are:
The Quadriceps (Front Thigh Muscles) which help straighten the knee and control knee bending.
The Hamstrings (Back Thigh Muscles) which help bend the knee and the Calf Muscles.
Other muscles such as your core, hip flexors and gluteal muscles in your buttock also help to stabilise and promote efficient knee motion.
The Key to Movement!
Just like any other joint in the body, the knee needs to have balanced muscular control for full efficient movement. This is achieved through accessory motion and proprioception.
Accessory motion
As well as the flexion and extension movements that you actively achieve in the knee, there are several other small movements that help it function smoothly—these are called accessory motions. These include anterior and posterior glide, rotation and distraction. When a chiropractor assess your knee, they will check the quality and quantity of these subtle movements.
These movements are important because they prevent excessive stress on parts of the knee and are monitored by little spirit levels in the tendons, joint capsule and ligaments. These spirit levels then tell the brain about the position of the knee, known as proprioception.
The Importance of Proprioception
This is what allows you to stand on one leg, walk without staring at your feet, or adjust your balance if you trip. The little spirit level receptors inside your body send signals to the brain. This information is then used to create coordinated movement and power in the right muscles at the correct time. This helps prevent injuries by providing stability and balance, reducing the risk of falls or faulty movements.
How to Keep Your Knees Healthy
To protect your knees and keep them strong:
✅ Strengthen your leg muscles, especially quadriceps and hamstrings.
✅ Maintain a healthy weight to reduce strain on the knee joint
✅ Stretch regularly to keep the joint flexible and muscles long.
✅ Avoid excessive impact, such as hard landings when jumping.
Coming Up:
Over the next two months we will discuss the most common knee complaints we see in the clinic as well as helpful tips on how to manage, and prevent them. In April, we will look at problems between the patella and femur, and in May, we will explore cartilage injuries.
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