Knee surgery

How does our knee work?

The knee is a hinge joint and the largest joint in the human body. Under normal use, the knee is often loaded with more than six times the body weight, and at the same time it must ensure sufficient mobility. The knee consists of two individual joints, the patellar joint (femoropatellar joint) and the actual knee joint (femorotibial joint). The thigh bone (femur), the tibia and the patella form the bony joint partners. For perfect gliding, the gliding surfaces of all joint partners are covered with a layer of cartilage. The menisci are located between the thigh and lower leg bones and increase the load-transferring surfaces of both joint partners.

These are signs of wear and tear of joint surfaces. This means that the joint cartilage layer has become thinner and/or partially worn away completely. In the further course of this disease, pain, inflammation of the joint capsule with swelling of the surrounding tissue and effusion formation in the affected joint may occur. If no improvement is achieved through physiotherapy or other forms of therapy, or if the pain is unacceptable or the quality of life is significantly reduced, the replacement of the damaged joint with an artificial joint is considered.

Other risks: osteoporosis (bone loss), overuse or overloading (e.g. in case of overweight), articular inflammation (e.g. due to rheumatic or metabolic disorders), accidents or injuries

If only one more operation helps

Once all conservative options have been exhausted, your doctor will talk to you about surgery. The goal is to significantly improve your quality of life again. The implantation of artificial knee joints has a long history in medicine and is now one of the most common procedures. Implants, technologies and methods have been continuously developed since then.

The artificial knee joint, also known as an endoprosthesis, consists of three parts: a femoral prosthesis (femoral component), a tibial prosthesis (tibial component) and the so-called inlay, which lies between the two parts as a sliding component. The femoral and tibial components of the artificial knee joint are usually made of cobalt-chrome alloys, while the sliding surface of the artificial joint is made of a special, very smooth and body-compatible plastic.

The artificial joint replaces the diseased parts of the joint that cause the discomfort through wear and tear. In the knee joint, usually only the diseased sliding surfaces of the joint are replaced. The femoral component for the thigh slides on a special plastic (polyethylene) that is fixed to the tibial component for the shin. All elements of an artificial knee joint work together in the same way as the natural joint. In the meantime, modern implants and surgical techniques are adapting more and more individually to the respective needs and circumstances of each patient and are intended to ensure pain-free mobility after arthrosis. For some years now, in addition to conventional joint replacement, patient-specific instrumentation has been used more and more. Here, special instruments are individually manufactured for your operation in order to be able to insert the optimal implant for you with an exact fit. The artificial joint replaces the diseased parts of the joint that cause the discomfort through wear and tear. In the knee joint, usually only the diseased sliding surfaces of the joint are replaced. The femoral component for the thigh slides on a special plastic (polyethylene) that is fixed to the tibial component for the shin. All elements of an artificial knee joint work together in the same way as the natural joint. In the meantime, modern implants and surgical techniques are adapting more and more individually to the respective needs and circumstances of each patient and are intended to ensure pain-free mobility after arthrosis. For some years now, in addition to conventional joint replacement, patient-specific instrumentation has been used more and more. Here, special instruments are individually manufactured for your operation in order to be able to insert the optimal implant for you with an exact fit.

Knee implants vary in shape, size and material depending on the clinical picture and stage of the disease. Depending on the situation or individual needs, the doctor can find the best solution for each individual patient.

How is the prosthesis connected to the bone?

The principle of cementless anchoring is used for biological anchoring. This means that the implant surface is in direct contact with the bone and that biological healing/adhesion “osseointegration” occurs. The bone remains active, grows together with the knee prosthesis and forms a biological unit. The shape and surface of the implants are of decisive importance for cementless anchoring. Stable and permanent anchoring is a basic requirement for the durability of the artificial joint.

A variety of anchorage forms are used to firmly connect the implant to the bone. A distinction is made between cemented, hybrid and cementless prosthesis anchoring. In hybrid and cemented restorations, this is done with bone cement. In this case, the tibial component (hybrid anchoring) and in some cases also the femoral component (cemented anchoring) are connected to the bone by means of a fast-setting plastic (bone cement). This form of anchoring has reached maximum stability very quickly, shortly after the operation.

In order to match the knee joint perfectly to your personal bone structure, anatomy and needs, your doctor selects the appropriate femoral and tibial components. In the next step, the worn joint surfaces on the femur and tibia are precisely removed and the remaining bone is prepared for the implant. The bone is modeled so that the implant fits perfectly in its bony environment. Depending on the type of prosthesis used, the knee prosthesis is either cemented into the bone, inserted without cement or screwed into place. An extremely smooth and low-abrasion plastic sliding surface is then clicked into the tibial component. All three parts make up the new knee joint.

• 1. cutting blocks are placed on the thigh/lower leg bones
• 2. femoral component is inserted
• 3. Tibial component is used
• 4. The plastic inlay is clicked into the tibial component
• 5. Femoral and tibial components and plastic inlay form the new knee joint