A comprehensive overview of knee replacement surgery. Let’s explore knee anatomy, common issues that may necessitate a replacement and the implantation process.
What to know about knee replacement? The knee is perhaps the most complex joint in the human body and plays a fundamental role in ensuring mobility and stability during daily activities.
Composed of various anatomical components including the femur, tibia, patella and ligaments, the knee is subjected to continuous stress and can sustain damage or degeneration over time.
It is estimated that more than half of people over 50 have experienced knee issues causing pain and difficulty in movement. 30% of these individuals suffer from osteoarthritis, which often only resolves with a knee replacement surgery.
Let’s learn more about the knee joint, the problems that can arise in this joint and treatment through prostheses.
Knee prosthesis: let’s start with anatomy
The knee has a complex synovial joint (the term “synovial” refers to the membrane and synovial fluid that line and lubricate mobile joints, allowing smooth and frictionless movement) between three main bones: the femur, tibia and patella. These bone components are stabilized by a series of ligaments, tendons and cartilages, which play a crucial role in knee functionality and mobility.
There are four knee ligaments in total:
- anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), which intertwine in the center of the joint, preventing excessive forward and backward movements of the femur relative to the tibia;
- medial collateral ligament (MCL) and lateral collateral ligament (LCL), which ensure the lateral stability of the knee.
The tendons surrounding the knee include the patellar tendon, which connects the patella to the tibia and the quadriceps tendon, which connects the femoral quadriceps muscles to the patella. These tendons are essential for transmitting muscle forces during knee flexion and extension.
The articular cartilage, present on the surface of the knee’s bone, provides a smooth and cushioning interface that reduces friction during movement. Meniscal cartilages, crescent-shaped, are located between the tibia and femur, contributing to load distribution and improving joint stability.
Understanding knee anatomy is essential to understand what happens when the joint becomes diseased or injured. These events compromise knee stability, causing pain and movement limitations. Intervening promptly as soon as these symptoms appear can allow for a full recovery of joint function and avoid surgical intervention and the post-operative course.
But what are the conditions that can affect the knee to the point of requiring a prosthesis?
Main knee problems
The knee is subject to various pathologies that may require a prosthesis to restore joint function, including:
- osteoarthritis, the most common form of arthritis, which occurs when the protective cartilage inside the knee deteriorates progressively;
- rheumatoid arthritis, an autoimmune disease that affects the joints, including the knee. Chronic joint inflammation can cause damage to cartilage, bones, and surrounding tissues;
- knee ligament injuries, such as anterior cruciate ligament (ACL) or medial collateral ligament (MCL) injuries, which can lead to instability and chronic pain;
- severe trauma, such as complex joint fractures or multiple soft tissue injuries, which can irreparably damage the knee;
- avascular necrosis. This is a condition in which a portion of the knee bone loses its blood supply and deteriorates. Avascular necrosis can be caused by various factors, such as the use of steroids or vascular diseases. In most patients, the cause is unclear.
In all these cases knee replacement surgery can restore joint stability and functionality, eliminating pain and movement limitations. But how is a knee prosthesis made? How is it implanted?
Knee prosthesis in detail
The knee prosthesis consists of artificial components. These simulate the anatomical parts of the natural joint.
The main components include: a femoral portion, which replaces the femoral joint surface; a tibial portion, which replaces the tibial joint surface; finally sometimes there is a patellar portion, which replaces the patellar joint surface.
Knee prostheses can be made using a combination of materials. These include metal alloys (e.g. titanium, cobalt-chrome) and high-strength polyethylene.
These are biocompatible and very resistant materials. The materials used guarantee maximum durability, even for more than twenty years after implantation.
Implantation of the knee prosthesis
The implantation of a knee prosthesis requires a specialist surgical approach. During the procedure the specialist fixes the prosthetic components to the knee bones. They use a combination of surgical cement or bone anchors.
The surgical procedure is performed under spinal anesthesia. It requires rigorous pre-operative preparation, accurate evaluation of the patient’s anatomy and knee conditions. Precise planning is also important to achieve correct joint alignment and stability.
Nowadays, where possible, attempts are made to apply minimally invasive surgical techniques. These are advanced surgical procedures aimed at reducing the extent of incision and tissue trauma during the intervention.
Specialists who adopt these methods use specialized tools and modern technologies. This allows for greater precision during the procedure and reduces the risk of post-operative complications.
Over the years knee prostheses have significantly improved in terms of design, material quality and bone fixation techniques. Knee prostheses can be either cemented or uncemented. The latter type is reserved for younger patients with good bone quality.
Therefore it is important to choose a specialized surgeon, who can identify the most appropriate type of implant.
There is also computer-assisted knee arthroplasty or computer navigation. This provides real-time information on the position and alignment of the knee joint during the procedure, allowing for improved accuracy in component placement. It is typically used in specific cases where traditional instruments might not suffice.
When osteoarthritis affects only a specific portion of the knee, a partial (unicompartmental) prosthesis can be used. This can be placed to replace only the diseased area of the knee, sparing the other structures.
It is the smallest implantable prosthesis in a knee and allows for resolving issues with a minimally invasive approach.
What happens if you don’t get a prosthesis?
Many patients fear undergoing knee prosthesis surgery. They want to avoid complications, additional pain and the postoperative recovery process. However, they often don’t realize that avoiding surgery can cause significant problems.
If a person with severe knee joint issues decides not to undergo prosthesis implantation, pathological conditions such as advanced osteoarthritis or serious injuries can worsen over time. The knee joint may suffer from chronic pain, stiffness, instability and limited mobility.
Additionally, the absence of a prosthesis can lead to progressive deterioration of the surrounding joint tissues, including muscles, ligaments and connective structures. These issues affect not only the integrity of the knee but also the overall health of the body. For example, if you experience knee pain, you might walk improperly to reduce the discomfort, which could eventually affect your back.
It’s important not to be deterred by potential complications related to knee surgery and to seek the immediate intervention of an expert orthopedic surgeon.
Can you feel the prosthesis inside your body after postoperative recovery?
A common question patients ask before knee prosthesis surgery concerns the sensations they will experience once the prosthesis is implanted.
When you have a knee prosthesis, you might feel a clicking sensation or hear a noise during certain movements. This phenomenon is known as “crepitus” and can be attributed to several factors:
- the prosthesis itself is made of artificial materials such as metal and plastic, which can generate a certain degree of friction or contact during joint movement;
- during the healing and recovery process after surgery the body forms a capsule of scar tissue around the prosthesis to stabilize it. This tissue can be elastic or fibrotic and its interaction with the prosthesis may contribute to the sensation of crackling.
It’s important to note that the presence of crackling is not necessarily indicative of a problem.
However, if the crepitus is accompanied by pain, swelling, limited movements or other suspicious symptoms, it’s advisable to consult your doctor for a thorough evaluation.
How do you sleep with the prosthesis?
Another frequently asked question by patients undergoing knee prosthesis surgery concerns the nighttime management of the prosthesis. Many of them were used to suffering from nocturnal joint pain and fear that the prosthesis might cause discomfort as well.
With a knee prosthesis you can sleep in any position you prefer. In the immediate postoperative period it’s advised not to place a pillow under the knee. Before going to bed it might be necessary to adopt pain management measures, especially in the first few months after surgery, such as applying ice or taking pain medications prescribed by your doctor to avoid compromising sleep quality.
Conclusions
Knee prosthesis is a medical solution that has transformed the lives of millions of people. This advanced surgical procedure offers a wide range of benefits, including significant improvement in mobility, pain reduction and a return to an active lifestyle.
It’s a highly successful procedure, but like all surgeries it carries potential risks. Therefore, it’s crucial to be operated on in a highly specialized environment.
If you suffer from knee pain or conditions such as osteoarthritis don’t hesitate to contact me. I am an expert orthopedic surgeon in Florence and with my experience I can identify the best treatment for your condition.
FAQ
What is a knee prosthesis?
A knee prosthesis is a medical device implanted in the knee joint. It replaces the damaged parts of the joint with artificial components to restore functionality and reduce pain.
What materials are used in knee prostheses?
Knee prostheses are generally made of metal alloys. The materials used are titanium or cobalt-chrome, which are biocompatible and offer strength and durability. The component that replaces the joint surface is made of polyethylene.
How long does a knee prosthesis last?
The lifespan of a knee prosthesis depends on various factors, including the patient’s age, physical activity level and adherence to postoperative recommendations. On average a knee prosthesis can last more than 20 years, but this can vary from case to case.
What are the risks associated with knee prosthesis implantation?
As with any surgical procedure there are potential risks associated with knee prosthesis implantation. These can include infection, bleeding, thrombophlebitis, damage to surrounding blood vessels, joint instability, residual pain and stiffness. However, with proper preoperative evaluation and surgery performed by an experienced surgeon these risks can be minimized.
What is the recovery period after knee prosthesis implantation?
The recovery period after knee prosthesis implantation can vary from patient to patient. It usually takes several months. During this period it’s necessary to follow a rehabilitation program that includes exercises to restore muscle strength, flexibility and joint mobility. The patient can gradually resume daily and sports activities under the guidance of the surgeon and physiotherapist.
