1. Home / 
  2. Patients / 
  3. Knee Joint

The Knee Joint

Learn more about the anatomy and damage of a knee joint, the fixation of an artificial knee joint and what happens before the surgery.

Anatomy: How is the Knee Joint Structured?

The knee joint essentially consists of three bone parts:

  • Thighbone (femur)
  • Shinbone (tibia)
  • Kneecap (patella)

On the joint surface of the thighbone, there are two bony protrusions, which are referred to as condyles. The joint surface of the shinbone is referred to as the tibial plateau. When in a healthy condition, both joint surfaces are covered with a layer of joint cartilage, that acts as a kind of shock absorber. The synovial fluid acts as a lubricant and enables smooth movements of the bones and reduces friction.
The menisci sit between the thighbone and the shinbone. The two menisci, medial and lateral, are crescent-shaped and consist of fibrocartilage. They enable force to be better distributed in the knee, thus protecting the cartilage-covered joint surfaces.
The kneecap is embedded in the tendon structure which extends from the thighbone to the shinbone. When the leg is stretched and flexed, the kneecap slides up or down thus stabilising the knee joint at the front.

Illustration: Anatomy of the knee joint

Role of the Joint Capsule
The knee joint is surrounded by a fixed articular capsule, which seals it off from the surrounding tissue. The articular capsule produces synovial fluid, which supplies the cartilage with nutrients and helps the knee joint to move free from friction.

Stability and Movement Thanks to Ligaments and Muscles
The knee joint is stabilised by a complex set of ligaments:
The collateral ligaments hold the joint in place on the inside and outside, while the cruciate ligaments stabilise the front and rear of the knee joint. This means the knee is a very stable joint despite being subject to considerable forces, whereby the powerful leg movements are supported by strong muscles.

What Happens Before Surgery?

Patient Assessment – Your Personal Medical History

In the initial consultation the doctor will ask you about your complaints. They will ask where you have pain and where this pain radiates to. They will also enquire about the intensity of the pain, how long it lasts and any influencing factors which exacerbate or ease the pain.

Physical Examination – Where Does it Hurt?

The doctor will first examine your knee, pelvis, hips and spine, and palpate the various muscle and bone structures. They will then conduct some movement tests to gain an impression of the mobility of the knee joint. They will also check the level of pain caused by various movements in the knee joint, such as rotation, bending and stretching.

X-ray – Focus on Your Knee

Using an X-ray image, the doctor is able to identify changes caused by knee arthrosis: Owing to a loss of cartilage, the intra-articular space between the femoral condyle and the tibial plateau is either no longer uniform, is narrower or is even no longer visible. The bone structure of the femoral condyle and tibial plateau, and in some cases the kneecap, appears irregular and altered; in very advanced stages the sections of the joint are deformed.

Preoperative Discussion – Your Chance to Ask any Questions

On the day before surgery, the surgeon will usually discuss the procedure with you in detail. During the consultation, they will explain the surgical method and the type of prosthesis to be used. Selecting the right prosthesis model depends on your individual bone condition, your body weight and your physical activity. The surgeon therefore normally decides beforehand which prosthesis model and type of fixation to use based on your X-ray and data.

On the day of the surgery, it is important that you are in a good general state of health. In light of this, it is important that you discuss any complaints you have with the attending doctor, whether it is a cold or a skin infection. While these conditions are harmless, they must be cured before a surgical intervention, in order to minimise any further risks.

An anaesthetist will also talk to you on the day before the operation to explain the potential risks involved with the anaesthesia. They will also perform a few minor examinations to check your heart and lung functions and rule out any possible allergies. They will then talk to you about the type of anaesthesia to be used.

Autologous Blood Donations – Find out More!

Under certain circumstances, a knee prosthesis surgery may result in considerable blood loss. In this event, a blood transfusion will then be required. An autologous blood transfusion using the patient's own blood, donated at an earlier date, essentially rules out the risk of infections such as Hepatitis C and HIV. There is normally enough time between the diagnosis and the knee prosthesis surgery (around two to six weeks) to discuss this issue with your attending doctor. Use this opportunity to ask about the option of an autologous blood donation.