The knee joint is considered the most weight-bearing and complex joint in the human body. Unlike other joints, the knee joint is made of three separate bones which are the femur (thigh bone), the tibia (shinbone), and the patella (kneecap). The stability of the knee joint is established by the muscle tendons attached to its bony parts. For extra stability, the knee joint is surrounded by four ligaments. Healthy joints should be able to provide bodyweight support and smooth articulation to help in doing everyday activities.
Evolution of Knee Replacement Surgery
No doubt that the knee joint is vital and essential for movement, therefore it is more vulnerable to injury and wearing out. Knee pain could be unendurable and a burden to live with. In the 19th century, doctors figured out that the articulating surfaces of the severely diseased or injured knee joint could be replaced with artificial parts. In 1860, the first attempt to restore knee joint mobility surgically was by Dr. Fergussen who proposed resection arthroplasty. Resection arthroplasty was a primitive surgery in which the articulating surfaces of the bones were resurfaced.
After a couple of years Dr. Verneil introduced interposition knee arthroplasty that involved placing soft tissues such as skin, muscle, fat, and pig bladder in between the articulating bones of the joint. Unfortunately, interposition arthroplasty failed to attain long-term results. Interposition arthroplasty has limited indications nowadays.
In the mid-twentieth, an American orthopedic doctor called dr. Campbell had heard about Dr. smith- Petersen hip mold arthroplasty and how successful it was. In the 1940s, Dr. Campbell managed to perform the first mold hemiarthroplasty of the knee by fitting an artificial implant made of Vitallium (an alloy of cobalt, chromium, and molybdenum that was used at the time) in the femoral condyle. Surgical implantation of a metallic prosthesis in the bones forming the joint was the milestone of the evolutionary development of orthopedic surgery.
In the 1950s, a Swedish orthopedic surgeon called dr. Borje Walldius performed for the first time bicompartmental knee arthroplasty. The design of the hinged prosthesis was a breakthrough back then as it aligned the replaced femoral and tibial surfaces and allowed them to articulate as a simple hinge. Walldius’s surgery was a success and had satisfactory results. However, the implanted hinged prosthesis failed to provide complex movement of the healthy knee joint.
Continuous collaboration between orthopedic surgeons and engineers paid off in 1971 when a Canadian doctor called Frank Gunston designed and performed the first polycentric knee arthroplasty. Dr. Gunston, who had both engineering and medical degrees, was inspired by the THA (total hip arthroplasty) performed by Dr. John Charnley. He succeeded in creating the first knee prosthesis that mimics the biomechanics of a healthy knee joint. polycentric knee arthroplasty refined the concept of low friction arthropathy and restoring natural knee kinematics by implanting metal on polyethylene prosthesis. Dr. Gunstone’s contribution paved the way for further modifications as his concept is still an integral component of making the prosthetic implants used nowadays.
Dr. Michael freeman was a British orthopedic surgeon and one of the pioneers of modern knee arthroplasty. Dr. freeman collaborated with prof. Swanson (prof. of mechanical engineering) to create the freeman-Swanson bicompartmental knee prosthesis that provided better mechanical alignment and stability. This prosthetic model prioritized the functionality of the knee joint that was better fulfilled by removing the cruciate ligaments. Freeman’s concepts are considered the basic steps toward total knee replacement.
In the early 1970s, English and Indian orthopedic surgeons called respectively Dr. John Insall and Dr. Chitranjan Ranawat were working at the HSS (hospital for special surgery) and could develop the first total knee replacement prothesis (total condylar prosthesis). The revolutionary design of Dr. Insall model was favored by the medical community and replaced the existing hinge-type implants because of its better range of motion. Dr. Insall’s prosthetic model resurfaced the three bones making the knee joint (tibia, femur, and patella). The total condylar prosthesis has become the prototype for the current knee implants as it not only achieved the native knee biomechanics but also preserved the cruciate ligaments. For such contributions, Dr. insall is considered the father of total knee replacement surgery.
The past six decades since 1970 till now had witnessed a series of technological developments and adjustments to different aspects of the total knee replacement including the material of the prosthetic implants and the technique of the surgery. These progressive modifications have resulted in the current forms and type of knee replacement surgery. Moreover, the published studies and research papers had contributed to a higher success rate and better outcome of the surgery.
Pros and Cons
Knee replacement surgery, which is also known as knee arthroplasty, is one of the most successful surgeries in all medicine hence it has become a quite common procedure. The US agency for healthcare research and quality (AHRQ) reported that more than 750,000 knee replacement surgeries are performed in the US in 2017. The current incidence of knee arthroplasties is believed to be doubled before 2030.
Over the past five decades, knee replacement surgeries had a high success rate proving their reliability and efficiency. Statistical studies have revealed that more than 90% of the performed knee arthroplasties showed excellent results and the knee implants provided durability and smooth articulation for 10 years after the surgery. The expected lifetime of the knee prosthesis varies according to the level of activity and the medical condition of the patient. Generally, a knee implant lasts for 15 to 20 years before getting worn out or loosened. If so, the patient may need a revision knee arthroplasty in which the implanted prostheses are partially or completely replaced with new ones.
Osteoarthritis patients who had undergone total knee replacement (TKR) showed remarkable improvement in knee articulation and full regain of its range of motion. Knee arthroplasties are believed to provide significant relief from chronic pain which is the most favored result of the surgery because pain is usually the chief complaint of patients with knee injuries. Knee arthroplasties renew your ability to resume your daily activities which will subsequently enhance your physical and psychological health.
To set realistic expectations for the surgery you should also consider the cons of knee arthroplasty. The prosthetic knee implant isn’t permanent, so a second surgery is possible after 10 to 25 years. In the case of arthritis, knee replacement surgery isn’t the cure for the underlying condition that resulted in knee injury, so patients will have to keep taking their prescribed medications. Most patients need to stay awhile in a rehabilitation center till they get used to their prosthesis. Whether the surgeon decides to perform knee arthroplasty with the traditional or the minimally invasive approach, a 3 to 12-inch scar over the knee is made. Like other surgical procedures, knee arthroplasty has its risks, yet the 90-days mortality rate is neglectable. Knee arthroplasties are a bit expensive and could be financially a burden for a lot of people.
Indications & Candidates for Surgery
Who is a good candidate for knee replacement surgery? orthopedic doctors decide whether their patients are eligible for knee arthroplasty or not based on multiple factors. The presented symptoms by the patients aren’t enough to indicate their eligibility for surgery, however, the severity and the duration of knee pain are also taken into consideration. Non-tolerable Long-lasting knee pain that showed no improvement with anti-inflammatories and analgesics may indicate the need for surgery.
First, doctors should have a detailed medical history and perform a clinical examination on the affected knee carefully. Then they ask for a radiological investigation to assess the degree of knee damage and deformity. There should be radiological evidence of irreversible deformity, liability to fracture, or bowing of the joint before considering surgery. If the patient is elected to knee arthropathy, he must get his blood tested for any infection that may affect the outcome of the surgery.
The common diseases that could be presented with the previously mentioned manifestations are:
1) Osteoarthritis
Osteoarthritis is a degenerative disorder that affects the articulating surfaces of the cartilages and bones forming joints. The articulating cartilages also act as protective cushions and covers for the bones, so when they wear out, they expose the covered bones to friction. The friction of the knee bones causes progressive pain, stiffness and may induce inflammatory reactions.
Primary (for unknown cause) osteoarthritis is the most common indication of knee arthroplasty. Osteoarthritis is more common among old people, obese and pregnant women. Orthopedics usually consider knee arthroplasty as a last resort for knee osteoarthritis as they prefer to start with conservative medications and lifestyle modifications.
2) Rheumatoid Arthritis (RA)
Rheumatoid Arthritis is an auto-immune disorder in which the human antibodies attack their own tissues by mistake, particularly the synovial membrane lining the joints. RA usually affects small joints first, yet an atypical course of rheumatoid could occur affecting knee joints.
Rheumatoid arthritis could affect joints on one or both sides, it is often presented with pain, stiffness, redness, and joint swelling that gets worse in the early morning. Rheumatologists usually choose a stepwise approach in treating RA as they start with immune-suppressive drugs. Late-stage RA that showed irreversible deformity in the knee joint indicates knee replacement surgery.
3) Hemophilia
Hemophilia is a hereditary coagulation disorder in which the body can’t synthesize a coagulative factor. Patients diagnosed with hemophilia have more tendency to bleed anywhere including joints causing a condition called hemophilic arthropathy.
Hemophilic arthropathy of the knee joint causes inflammatory responses that eventually lead to the destruction of the joint cartilage and synovial membrane. Uncontrolled hemophilic arthropathy of the knee joint may result in a disability and in such a case, a knee replacement surgery is recommended.
4) Gout
Gout is a form of arthritis characterized by an increased level of uric acid in the blood. Uric acid, which is a natural product of the metabolism of proteins and excreted mostly by the kidneys, accumulates in the bloodstream in some susceptible patients. Elevation of the uric acid level in the blood leads to its deposition in the joints causing severe inflammation, pain, stiffness, and eventually destruction.
Although gout usually affects the joint of the big toe first, it could also affect the knee joint at some point of its progression which will indicate knee arthroplasty.
5) Osteonecrosis
Osteonecrosis is a medical condition in which the bone tissue dies due to reduced blood supply. Usually secondary to other underlying causes such as trauma or bone disease. Neither rare nor common as its prevalence rate is about 15,000 patients in the United States per year.
in case of knee joint affection, an orthopedic doctor has to assess the severity of the condition before deciding whether the joint need to be replaced surgically or not.
6) Trauma
Trauma isn’t a common indication for knee replacement surgery because this irreversible decision must be for severely damaged knee joints. knee joint traumas involving fractures are usually treated with reduction and fixation using a cast.
Contraindications
When shouldn’t I have knee arthroplasty? There are a few contraindications to knee replacement surgery, they include the following:
- Active infection is an absolute contraindication to knee arthroplasty because it may result in the spreading of the infection and sepsis. In such a case, the surgery should be postponed till the patient is completely cured.
- Uncontrolled coagulopathy is a medical condition in which the blood abnormally tends to bleed or to coagulate. If a patient with uncontrolled coagulopathy undergoes any surgery, he will be at a life-threatening risk to bleed excessively. Almost all patients should get a bleeding profile before having any surgical procedure.
- Pregnancy is a relative contraindication to knee arthroplasty as surgeons usually avoid any kind of surgical approaches during pregnancy. however, emergencies and urgent calls for surgery could be a green light to perform knee arthroplasty carefully by a surgical team including an obstetrician.
Types (Detailed)
The two main types of knee replacement surgeries are total and partial (unicompartmental) knee arthroplasty. There is other less commonly performed types of knee arthroplasty such as patella-femoral replacement (PFR) and cartilage replacement surgery. Although both are successful procedures, controversy exists over the effectiveness and long-term results of partial knee arthroplasty compared to total knee arthroplasty. Each surgical procedure is designed for certain indications and has its advantages. Therefore, Orthopedic doctors always choose the most suitable approach according to the patients’ needs.
Total Knee Arthroplasty (TKA) is a surgical procedure involving removing the articulating surfaces of both the shinbone and thigh bone which are called respectively the tibial plateau and the femoral condyles, then replacing them with artificial implants. TKA is usually performed under regional anesthesia and takes about 1 – 3 hours according to the experience of the orthopedic surgeon.
Partial Knee Arthroplasty which is also called unicompartmental and unicondylar knee arthroplasty is one of the most cost-effective surgeries. The procedure is as referred to by its name include partial replacement of the articulating surfaces of the knee joint, as only one side of the joint whether the medial or the lateral side is being replaced by a prosthetic implant. The operation time of partial knee arthroplasty is 1- 2 hours.
Prosthetic Implant
The design and size of the prosthetic implant are usually chosen to fit the patient’s needs, whereas the material of the implant is usually made of titanium or cobalt-chromium.
The spacer inserted between the implanted surfaces of the shinbone and the femur is made of polyethylene (plastic). The spacer is used as a shock-absorber, and it allows full range of motion. The prosthetic parts are fixated in place by using cement or osseointegration (direct attachment between the bone and the implant).
Recovery and Rehabilitation
How long could the patient walk normally after knee arthroplasty? The time needed for patients to recover and regain their strength is variable according to their age and health condition. After the surgery, patients should stay in the hospital for post-operative assessment and care. The process of recovery is as crucial as surgery because it contributes to getting the best outcome of the surgery. Patients get discharged from the hospital a few days after the surgery and they will be referred to a physiotherapist.
The physical therapist will set a rehabilitation program that the patient will follow for at least a month. During this month, patients are usually asked to use walking aids like crutches and canes to avoid recumbency and muscle wasting. Mostly, patients could walk on their own after 6 weeks of the surgery. The rehab program will also include home exercises and functional goals to help patients get clued in their progress. Doubtlessly, it is essential to schedule your follow-up visits with your physical therapist and to follow his instructions and precautions.
At the rehabilitation center, patients perform specific muscle-targeting exercises under the supervision of a physical therapist to help patients adapt to their prostheses. First, the therapist will ask the patient to use CPM (continuous passive motion) machine that moves his knee passively. Then patients will be asked to perform simple balance exercises that will gradually increase in their intensity. Finally, after one-two months patients could resume their daily activities normally.
Complications & risks
Knee arthroplasty is a major surgery, and many people may consider it risky, yet the incidence of complications is low. The orthopedic surgeon should discuss the procedure in detail before surgery and inform the patient about the possible complications. The complications of knee arthroplasty are mostly preventable and manageable, they include:
- Deep venous thrombosis (DVT) is a medical condition in which the blood clots in a deep vein particularly in the lower limb. DVT usually occurs due to recumbency and reduced blood flow in the veins. Some studies showed that the incidence of DVT after joint arthroplasty is up to 17%. DVT could be life-threatening and cause ischemic sequelae.
- Infection is a serious complication that directly affects the result of the surgery. patients can catch infection during or after surgery, so doctors always ask their patients to take care of their wound and avoid exposing it to moisture. Prophylactic broad-spectrum antibiotics could be prescribed for susceptible patients.
- Nerve injury isn’t a common complication of knee arthroplasty. however incompetent surgeons are more likely to cause nerve damage.
- Bleeding is less likely to occur unless the patient is coagulopathic. Coagulopathic patients are whose blood forms more or fewer clots than normal. Bleeding could also occur during surgery due to vascular injury. Fortunately, bleeding is controllable in most cases.
- Intra-operative bone fracture is reported in patients who previously had osteoporosis (weakened bones). Bone fractures are more common in women and old patients.
Costs
If your orthopedic doctor decided that you need knee arthroplasty, you should consider its expenses. Knee replacement surgery is an expensive procedure because the prosthetic implant, as well as operating surgeons, costs a lot. The cost of knee arthroplasty fluctuates in a wide range according to many factors. The average cost of total knee arthroplasty in the United States is 55,000 $, whereas the average cost of partial (unicompartmental) knee arthroplasty is 45,000 $.
Fortunately, most health insurance companies cover knee replacement surgeries as a part of their standard package. Take into consideration that health facilities in different countries don’t charge the same for knee arthroplasty. It is believed that the health service in the US is over-priced, thus many patients have knee arthroplasty abroad. Hospitals in countries such as Turkey, India, Egypt, and South Africa provide excellent health services at much lower prices. It is better to financially consider the additional fees of the rehabilitation center and physical therapy. Furthermore, the longer you stay in the hospital, the more you are charged.
Alternatives
Patients who can’t undergo knee arthroplasty may need to get another line of treatment. In such a case, pain-relieving is the main goal. Thus, Patients may need to get intra-articular steroid injections to reduce the pain and swelling. As a matter of fact, other alternatives to knee replacement surgery are limited and less effective. Current FDA guidelines may not recommend some of them as their benefits are still under research. These alternatives are the following:
- Bone marrow aspirate concentrate (BMAC)
- Platelet-rich plasma injection
- Acupuncture