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Total or Partial Knee Arthroplasty - Knee Endoprosthesis
Knee arthroplasty is a surgical procedure involving the implantation of a knee prosthesis. This procedure is employed not only when the natural structures of the knee joint wear out due to aging but also when they are damaged as a result of trauma. Unfortunately, the knee joint’s anatomy predisposes it to such issues. The knee is the largest joint in the human body, connecting the thigh to the lower leg. It serves a critical function by bearing the entire body’s weight, stabilizing posture, and facilitating movement during daily activities and sports. The knee is a complex joint—a hinge-and-rotation joint—comprising numerous components such as bones, menisci, and ligaments, all encapsulated by a joint capsule. Degeneration of the knee joint weakens its structures and damages the articular cartilage.
A knee prosthesis is an implant made from biocompatible materials that replace damaged joint tissues. Knee joint replacement is performed during a surgical procedure called arthroplasty. The implant is used to fill the gaps in the joint surface caused by tissue loss. Depending on the extent of cartilage damage, the replacement can be total or partial. The procedure aims to restore normal joint function and ensure adequate stabilization during movement. Unfortunately, a knee prosthesis is not permanent. It is estimated that a knee prosthesis should serve the patient for at least 15 to 20 years, but its actual longevity depends on several factors such as body weight, anatomical structure, and usage of the limb.
When is Knee Arthroplasty Necessary?
Various knee conditions, including knee osteoarthritis, can initially be treated non-invasively to avoid surgery. Orthopedists may recommend treatments such as intra-articular steroid injections with pain relievers, platelet-rich plasma (PRP), Orthokine preparations, hyaluronic acid, or popular glucosamine and chondroitin sulfate supplements. However, it is essential to note that these methods do not directly cure the root cause of the condition but only slow its progression. In more advanced cases, knee arthroplasty becomes the solution offering hope for patients to regain normal functionality.
Osteoarthritis of the knee is a condition with a multifactorial etiology. Various factors may predispose individuals to its development, such as lifestyle or occupational factors (e.g., prolonged standing with significant leg strain), past injuries to the lower limbs, or genetically determined limb axis abnormalities.
When the articular cartilage, which cushions the joint and provides smooth surfaces for the femur and tibia to move against each other, deteriorates or wears out completely, the bones begin to rub directly against each other, becoming rough and coarse. This triggers an inflammatory process, causing pain, knee stiffness, and difficulty walking. In contrast, implants used in knee replacement have smooth surfaces. The decision to recommend a knee prosthesis for treating joint inflammation depends on several factors, including the condition of the knee, the patient’s age, and activity level.
Common Symptoms of Knee Osteoarthritis:
- Knee pain, often occurring during movement.
- Difficulty walking up and down stairs due to increased pain.
- Inability to fully straighten or bend the leg due to restricted joint movement.
- Morning stiffness or stiffness after periods of inactivity, such as getting up from a chair.
- Characteristic creaking sounds caused by friction between joint surfaces.
- Formation of bony growths (osteophytes) on the joint surface.
Types of Knee Joint Prostheses
Over 150 types of knee prostheses are currently available for surgical application. The type of implant chosen depends on the specific knee problem as well as the patient’s age, body weight, overall health, and activity level. The primary components of implants are made from metal alloys (cobalt/chromium) or metal-ceramic composites (oxidized zirconium) and durable plastic materials (polyethylene).
In total knee replacement, one of the most commonly used implants is the posterior-stabilized knee prosthesis. In this design, the cruciate ligaments are removed, and part of the implant replaces their function. Another frequently used implant is the cruciate-retaining knee prosthesis. It is important to note that selecting the appropriate type of prosthesis for a patient is an individual decision made by the doctor.
In most cases, the knee prosthesis used includes a tibial insert fixed in place. This means that the polyethylene tibial component is attached to the metal implant, and the femoral component slides over this smooth surface. For prostheses with a mobile insert, the polyethylene insert can move slightly within the metal tibial component. This design aims to provide patients with greater joint mobility.
Regarding the fixation of implants, three types are available:
- Cemented fixation, which uses quick-setting bone cement.
- Cementless fixation, which relies on new bone tissue growing into the implant surface.
- Hybrid fixation, where the femoral component is cementless, and the tibial and patellar components are fixed with cement.
What Does Knee Arthroplasty Involve?
Knee arthroplasty is divided into two types: total knee replacement, where the entire joint is replaced with an artificial surface, and partial knee replacement, where only one damaged component of the knee is replaced. In total knee replacement, which is more common of the two procedures, damaged bone and joint cartilage are removed and replaced with artificial implants tailored to individual needs to ensure maximum compatibility.
Before the procedure, the patient is administered either general anesthesia (the patient is unconscious during the operation) or regional anesthesia (a temporary nerve block to prevent pain in the operative area).
The procedure begins with the orthopedic surgeon making an incision in the knee and moving the kneecap aside to access the joint. The two menisci and the anterior cruciate ligament (ACL) are then removed. Depending on the type of prosthesis, the posterior cruciate ligament (PCL) may be retained or removed. During the main phase of the operation, the proximal tibia, distal femur, and cartilage—often accompanied by small bone spurs characteristic of osteoarthritis—are removed. The femur and tibia are then covered with metal implants to recreate the joint surfaces. If the patella has also deteriorated, its surface can be replaced with a polyethylene implant, though this is rarely done. The procedure concludes with layer-by-layer suturing of the wound. Total knee replacement surgery generally takes about 90 to 120 minutes, and most patients stay in the hospital for approximately a week.
Are There Any Complications Associated With Knee Arthroplasty?
Complications after knee arthroplasty are relatively rare but, given the extensive nature of the surgery, may involve serious consequences, such as:
- Deep vein thrombosis: This occurs due to immobility during the perioperative period.
- Vascular damage: Injury to blood vessels during surgery.
- Pulmonary embolism: A potentially life-threatening complication.
- Infection: The risk of surgical site infection or systemic bacterial infections is present. To prevent this, antibiotics are administered for a short period post-surgery. Severe infections may necessitate a second surgery, involving wound cleaning and implant replacement.
- Nerve damage: Surrounding nerves or blood vessels may be injured during the procedure, which can cause significant discomfort.
- Pain and swelling: Postoperative pain or swelling is common to varying degrees.
- Mechanical complications: In the long term, issues such as loosening or dislocation of the prosthesis may occur. The risk is higher when the joint is subject to increased strain from high activity levels or excessive body weight.
Most complications can be addressed with appropriate surgical or conservative interventions, such as blood-thinning medications for thrombosis or additional surgery if fractures occur near the implant.
How Long Does Rehabilitation Take After Knee Arthroplasty?
The first few weeks of intensive rehabilitation focus on reducing pain and swelling, restoring full range of motion, and rebuilding muscle strength. The patient must use two elbow crutches for mobility for a period of four to six weeks, as determined by the attending physician. After discontinuing the use of crutches, the patient may begin driving a car.
Early physiotherapy typically includes the use of Continuous Passive Motion (CPM) machines and passive exercises. These simple activities help prepare the operated knee for further rehabilitation. Postoperative rehabilitation aims to restore muscle strength and improve mobility in structures directly related to the knee joint's functionality. Special attention must be paid to offloading the operated joint (e.g., lying down or sitting).
The next phase involves gait training, including walking up and down stairs under the close supervision of a physiotherapist. Sensorimotor exercises are introduced to aid in rebuilding superficial and deep sensory perception in the surgical area, accelerating the recovery of proper neuromuscular function.
What Should Be Avoided After Knee Arthroplasty?
- Do not stop using crutches too soon: Orthopedic equipment such as walkers, crutches, or braces should be used as directed by the physician until clearance is given to discontinue them.
- Avoid wearing unstable footwear: Flip-flops, slippers, and other unstable footwear can lead to slipping or twisting the leg in a way that the newly operated knee may not handle.
- Do not lift heavy objects: Avoid lifting heavy items for several weeks post-surgery to prevent excessive strain on the operated joint.
- Do not drive immediately after surgery: Driving is generally considered safe after about six weeks.
- Avoid low chairs: Low chairs, soft couches, or rocking chairs require significant leg strain when standing up, which should be avoided.
- Avoid walking on uneven terrain: Uneven surfaces can lead to tripping, twisting, or falling, risking injury to the operated leg.
Can You Kneel with a Knee Prosthesis?
Many patients are concerned about kneeling with a knee prosthesis or report difficulties in doing so. However, if this position feels uncomfortable, it is best to avoid kneeling. There is no clinical evidence suggesting that kneeling shortens the lifespan of the prosthesis. It is important to note that the implant is designed primarily for walking, and any discomfort experienced by the patient while kneeling after arthroplasty does not indicate the failure of the treatment.
How Long Does Knee Pain Last After Arthroplasty?
This aspect is highly individual, as each patient has a unique pain threshold. Additionally, postoperative discomfort depends on the patient’s pre-surgery condition. Generally, the expected results of the surgery become noticeable after 4–6 months of rehabilitation.
Can You Still Be an Athlete After Knee Replacement?
Replacing a damaged knee joint with a prosthesis does not prevent a return to physical activity. However, it is essential to remember that the primary goal of knee arthroplasty is to improve joint mobility and reduce pain caused by the degradation of joint surfaces. The knee implant is artificial and does not regenerate, so its lifespan is closely tied to how it is used.
For this reason, it is advisable to avoid activities that put the joint at risk of injury, such as football, handball, basketball, athletics, martial arts, and winter sports like ice skating, skiing, and snowboarding. These sports involve repetitive movements or increased joint strain, which can lead to wear and tear or injury. Such injuries can have more severe consequences for patients with a prosthetic joint than for those with a "biological" knee.
Safe sports for patients after knee arthroplasty include cycling and swimming. Patients interested in returning to their favorite physical activities after surgery should consult their doctor before qualifying for knee arthroplasty.
Rehabilitation After Knee Arthroplasty
As rehabilitation progresses, the physiotherapist will gradually increase the difficulty and complexity of exercises. Strengthening exercises can eventually be performed in standing positions and supplemented with stationary cycling. It is important to remember that knee replacement surgery is only half the battle—successful rehabilitation ultimately determines the outcome.
According to specialists, rehabilitation after knee arthroplasty typically lasts about six months. However, this timeframe may vary and is always adjusted individually by the doctor and physiotherapist for each patient. Proper attention to these aspects is crucial, as well-conducted postoperative rehabilitation is essential for regaining full mobility.
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