Knee Replacement
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The surgical procedure of knee replacement (knee arthroplasty) involves replacing parts of damaged or deteriorated knee joints with artificial parts made of plastic and metal to alleviate pain and improve knee function. It’s most commonly used to treat pain and stiffness in the knee joint caused by osteoarthritis. Depending on the damage to the knee, it can be used to replace all of your knee joint (total knee replacement) or some of it (partial knee replacement).
The first surgery of this type was performed in 1968. Since then, improvements in materials and surgical techniques have greatly increased its effectiveness. Before the procedure, the specialists will evaluate the knee’s strength, stability, and range of motion, and will use images to assess the extent of damage, to determine if knee replacement is the appropriate option. The choice of joints type and surgical techniques is based on several factors such as age, weight, activity level, knee size and shape, and overall health.
Indications
Implants
Procedure
Recovery
Complications
Indications
A knee replacement operation is usually indicated in the following cases:
- severe knee pain or stiffness that limits daily activities, including walking, climbing stairs, and standing or sitting in a chair,
- in the case of a knee that has become flexed and no longer extends as a result of severe osteoarthritis,
- chronic inflammation and swelling of the knee that does not improve with rest, ice, hyaluronic acid or cortisone infiltrations,
- Inward (varus) or outward (valgus) knee deformity, in which other surgical interventions are not possible.
Most patients who have a knee replacement suffer from pain and flexibility problems caused by osteoarthritis (see below). Other conditions a knee replacement may be used to treat include gout and sports injuries, but this is not common.
Implants
Different knee implants are used in the procedure, categorized by the materials that interact during knee flexion:
- Metal on plastic: Common type, with a metal femoral component on a polyethylene plastic spacer. It’s cost-effective and has a well-established safety record.
- Ceramic on plastic: Uses a ceramic femoral component or a metal one with a ceramic coating on a plastic spacer. Suitable for those sensitive to nickel, but may lead to immune reactions.
- Ceramic on ceramic: Both femoral and tibial components are ceramic, minimizing body reactions. However, they can produce a squeaking noise and, in rare cases, may shatter, requiring surgery.
- Metal on metal: Both components are metal. Less common due to concerns about metal traces entering the bloodstream, causing inflammation and organ damage. Considered for young, active men seeking longer-lasting implants.
There are also other materials gaining prominence with the increasing demand for flexibility and agility in prosthetics. A new ceramic total knee replacement is starting to be available in some hospitals after clinical trials. Similarly, Polyetheretherketone (PEEK) and carbon-fiber-reinforced PEEK (CFR-PEEK) have been successfully used in the field of orthopedic implants.
Knee prostheses are also distinguished based on the condition of the cruciate ligaments. If the ligaments are in good condition, an attempt is made to preserve one or both cruciates resulting in a less invasive intervention.
Alternatively, there are interventions that involve the replacement of the cruciate ligaments. In this case the prosthesis is called posterior-stabilized, a mechanism that guarantees excellent recovery of functionality, especially with modern minimally invasive surgery protocols.
In cases with complex deformities or ligament damage, semi-constrained or constrained prostheses can be used. However, they guarantee the disappearance of pain and the patient can resume normal daily activities.
Procedure
The knee replacement consists in removing the damaged parts of bone and cartilage, replacing them with artificial parts having the same shape. An incision is then created in the front of the knee and the damaged cartilage is removed. The damaged surfaces of the femur, tibia and patella are then prepared using a special instrument. The part that will be added includes a femoral part, a tibial part and sometimes a patellar part. They can be implanted in the bone regardless of the presence or absence of cement. Using a computer you can evaluate the correct positioning. The surgery can be performed under spinal anesthesia or general anesthesia.
An operation of this type lasts approximately 90 minutes and is performed during a hospital stay which lasts approximately 5-7 days. Post-operative pain is controlled through painkillers or by following other pain therapy techniques indicated by the professional.
The knee arthroplasty is usually carried out using robotics. The robotic system assists the surgeon during the implantation procedure and allows to drastically reduce knee prosthesis positioning errors, which are the cause of most failures and complications. The robotic technique in fact allows the surgeon to be certain of the exact positioning of the prosthesis during its application. The two most used knee robots are Mako and Navio systems.
Recovery
The day after surgery, the patient will be helped by the physiotherapist. After just a few days you start going up and down the stairs, always with the help of a physiotherapist. After hospitalization in orthopedics, rehabilitation can be carried out in a Rehabilitation Department or through a physiotherapist in an outpatient clinic.
Resumption of driving is possible after just 2 months. Returning to work, however, depends greatly on the type of job. One that is more office-style or at least less physical, allows for a quicker return. Sports activities can be resumed gradually after approximately 3 months.
The results of this surgery are very encouraging: a complete disappearance of pain, a rapid recovery of mobility, normal daily activities and muscle strength. Normal movement without lameness is achieved within one month of surgery. The average lifespan is approximately 20-25 years. In any case, after 20 years, 90% of implanted prostheses are still stable and do not present any particular problems. With the progress of surgical techniques and materials used, the results can be continuously improved.
Complications
For this type of operation there are specific risks in addition to those typical of any surgical procedure:
- Stiffness in the joint in case post-operative rehabilitation was not performed correctly.
- Formation of a hematoma due to bleeding inside the joint.
- Infection, although now a rare event (risk less than 1%), becomes a serious complication. In addition to requiring the start of antibiotic therapy, there is the risk of having to change the entire prosthesis. When symptoms of an infection are recognized early, a simple surgical wash together with antibiotic therapy may be sufficient.
- Formation of small blood clots that can form and get stuck in the veins of the legs, requiring anticoagulant therapy for several weeks. Through correct heparin therapy for several weeks after surgery, this problem should no longer occur.
A complete list of complications should be provided to the patient prior to any procedure at the time of treatment discussion.
Knee Osteoarthritis (Gonarthrosis)
The most common disease that leads patients to undergo knee replacement surgery is knee osteoarthritis.
It is a condition characterized by joint pain, inflammation, and stiffness. It commonly affects the knees, which are the largest and most powerful joints in the body. Knee arthritis can be a severe and disabling condition.
Symptoms
Causes
Diagnosis
Complications
Treatment
Symptoms
The pain that characterizes gonarthrosis is dull and mechanical, therefore it manifests itself when the knee is set in motion and attenuates when it is at rest.
The disorder initially manifests itself following prolonged activity of the joint, but, in the case of a more complex arthritic picture, the pain can affect the patient even following very simple movements, such as that carried out to get up from a chair or to get out of a car.
Other symptoms of gonarthrosis include swelling of the affected area and stiffness of the joint upon movement. Furthermore, a joint effusion may progressively form, caused by an overabundant production of synovial fluid present in the joint cavity and which limits movement.
Causes
There are several possible causes of knee arthritis, including:
- Age: The risk of developing knee arthritis increases with age. As people get older, the cartilage in their joints naturally wears away.
- Genetics: Knee arthritis may run in families, indicating a genetic predisposition to the condition.
- Gender: Women are more likely to develop knee arthritis than men.
- Previous knee injuries: Injuries to the knee, such as fractures, ligament tears, or meniscal tears, can damage the joint and increase the risk of developing arthritis later in life.
- Obesity: Being overweight puts extra stress on the knee joint, which can lead to the development of arthritis.
- Repetitive stress: Jobs or activities that require repetitive knee movements, such as squatting or kneeling, can increase the risk of developing knee arthritis.
- Infection: In rare cases, an infection in the knee joint can lead to arthritis.
- Autoimmune disorders: Certain autoimmune disorders, such as rheumatoid arthritis, can cause inflammation in the knee joint and lead to arthritis.
Diagnosis
The diagnosis of knee arthritis typically involves a combination of medical history, physical examination, and imaging tests. The doctor will start by asking the patient about their symptoms, including the location and severity of pain, how long the pain has been present, and any factors that seem to worsen or improve the symptoms. They will also ask about any previous knee injuries or surgeries, family history of arthritis, and other medical conditions. During the physical examination, the doctor will examine the knee for signs of swelling, redness, warmth, and tenderness. They may also check for range of motion, muscle strength, and stability.
Imaging tests such as X-rays, MRIs, and CT scans may be ordered to help confirm the diagnosis and determine the extent of the damage to the joint. Blood tests may also be performed to rule out other conditions that can cause similar symptoms.
Complications
Knee arthritis can cause a range of complications, such as pain, stiffness, swelling, and reduced mobility. It can also lead to muscle weakness and loss of function in the affected knee. Over time, the joint may become severely damaged, leading to bone-on-bone contact, which can cause even more pain and further limit mobility. Additionally, people with knee arthritis may be at increased risk for falls and fractures, particularly if they have reduced mobility or balance issues. In some cases, knee arthritis can also lead to depression or anxiety due to the chronic pain and limitations it can cause.
Treatment
Depending on the severity of the joint degeneration, different solutions can be used to slow the progression of knee osteoarthritis.
Among these are:
- anti-inflammatory medications, associated with physiotherapy, especially if knee osteoarthritis has been diagnosed early.
- hyaluronic acid injections: which can help in this phase of the disease, as they have a strong lubricating component which reduces the consequences of direct contact between the bones.
- regenerative medicine solutions, such as PRP and stem cells, which offer a valid solution in slowing down progression and controlling symptoms, with particularly promising results.
- knee prosthesis implantation, in the advanced stages. Surgical choices are different based on the degree of impairment of the knee cartilage and the patient’s characteristics.
The primary goal of undergoing a knee replacement procedure is to alleviate pain and enhance mobility, ultimately improving one’s overall quality of life. While some may believe that the completion of a successful surgery marks the resolution of the issue, it’s crucial to recognize that surgery alone is only a part of the solution. Despite the surgeon’s skillful efforts, the patient plays a pivotal role in maximizing the benefits of the surgery. Following the prescribed physical therapy regimen is imperative for a successful recovery.
Rehabilitation serves as a key component in expediting the return to a normal, independent lifestyle over the long term. It addresses pain relief, strengthens the muscles surrounding the joint, enhances stability, aids in fall prevention, promotes blood circulation, and manages swelling. Surprisingly, initiating the rehabilitation process on the day of surgery completion, once the patient has recovered from anesthesia, is considered optimal. The typical rehabilitation program spans three weeks, after which the patient can continue exercises at home.
Deviation from the prescribed physical therapy plan may lead to an extended healing period, potential injuries to the new joints and supportive muscles, and an increased risk of future revision surgery. With diligent adherence to the rehabilitation program, most patients can enjoy a pain-free life approximately six months to a year post knee replacement surgery.
