Background and history of Knee Arthroplasty
Knee replacement is considered an important achievement in orthopaedic surgery. The development of the total knee replacement procedure began back in 1860 when a German surgeon surgically implanted the first primitive hinge joint made of ivory, giving the patient a greater quality of life and restoring the function of the knee joint. The introduction of the acrylic Walldius hinge joint in 1951 was followed by the development of the knee arthroplasty in 1960 based on the John Charnley’s cemented metal-on-polyethylene total hip replacement. The surgical outcome has been improved due to changes in the designs of the implants and the development of new and better instrumentation. The modern arthroplasty is a procedure with long-lasting results and functional improvement. About 3.48 million total knee replacements have been estimated to be performed annually in the USA by 2030. Nowadays, it is considered a safe surgical procedure with positive patient’s outcomes. Its main purpose is to improve the knee function while reducing the joint pain.
Relevant anatomy of the Knee
The knee is a joint composed of four bones: the femur, the tibia, proximal part of the fibula, the patella. Moreover, there are two fibro-cartilaginous discs or menisci: external and internal meniscus. The menisci are a very important component of the joint due to their specific function. There are different ligaments supporting the joint: anterior and posterior cruciate, internal and external collateral, and the patellar tendon. Nowadays the total knee arthroplasty uses cobalt-chromium as material for the femoral and tibial components. Recently, oxidized zirconium or ceramic prosthesis have been developed. These new components have demonstrated better patients outcomes.
Indications of Knee Replacement Procedure
There are three common reasons to perform this type of surgery:
- Osteoarthritis: This type of arthritis is an age-related disease mainly affecting people over 50 years old, caused by inflammation, breakdown and damage of the articular cartilage around the joint.
- Rheumatoid arthritis: This type of arthritis is characterized by inflammatory changes of the knee joint due to an autoimmune disorder . The damage and stiffness of the knee joint can induce pain and limit movements.
- Post-traumatic arthritis: In these cases, arthritis or inflammation is secondary to a trauma.
Contraindications of the Knee Replacement surgery
- Evident signs of infection or sepsis.
- Presence of well-functioning knee arthrodesis.
- Severe circulatory insufficiency.
- Extensor mechanism dysfunction.
- Recurvatum deformity secondary to muscular weakness
The evaluation before the surgery is a very important step that must be done. It consists of several phases such as medical history and physical examination with the aim to assess motion, flexibility, and strength of the knee joint. X-rays need to be performed to evaluate or demonstrate deformity in the knee joint. Other tests need to be done such as a blood test and MRI with the goal to demonstrate the current condition of the bone and soft tissues of the knee.
The orthopaedic surgeon will perform and/or review all these exams and will advise whether to perform the surgery or to proceed with other options such as medications, injections and physical therapy.
Details of the procedure
Total knee replacement is a very complex surgery. It requires an orthopaedic surgeon to carefully remove the affected portion of the bone and to reshape the healthy portion having it ready to accommodate the implant. The artificial joint will restore the ordinary function of the knee. The surgeon makes an incision on the front of the knee to make the patella accessible to him. Then the patella will be rotated to have a better visual of the operative field. The metal femoral component will be implanted on the distal end of the femur. The tibia is prepared to fit the metal part. Once everything is implanted, the surgeon needs to readjust the patella to ensure that it fits in the new artificial joint. The orthopaedic will then bend and flex the knee to ensure everything is working and in the right place. The incision will be sutured using nylon or absorbable materials.
There are two types of knee replacement surgery:
- Total knee replacement: It is the most common procedure. The surgery involves the replacement of both sides of the knee joint. The operation can take from 1 hour to 3 hours. The patient will have less pain and better mobility. The main inconvenience is the formation of scar tissue because it might make it difficult to move the knee after the surgical procedure.
- Partial knee replacement: It replaces only one specific side of the knee joint. The incision will be smaller but the recover in functionality will not be as great as the total knee replacement operation. There is a lower risk of infection and blood clots. It is advised for some patients who have partial articular damage affecting specific anatomical regions of the knee joint.
Recovery process after the knee replacement surgery
The patient can be hospitalized for one to three days. The duration of the in-hospital stay is going to be related with the response of the patient to the rehabilitation. The physical therapy needs to be performed as part of the treatment with the aim to strengthen the knee both before and after the procedure. The patient should have some support from family or friends as the physical therapy needs to continue at home once the patient is discharged from the hospital whilst the recovery will still be ongoing, and the patient won’t yet be 100% self-sufficient. The patient will then need to be evaluated by the doctor as follow up after surgery.
Complications of the knee arthroplasty procedure
- Infection which affects fewer than 2 % of patients
- Fracture during or after the surgery.
- Nerve damage leading to numbness or weakness
- Continued pain or stiffness
- Blood clot in the leg, known as DVT (deep venous thrombosis)
- Pulmonary embolism secondary to the DVT
- Bleeding in the knee joint
- Excess scar tissue with a consequent limitation of movement of the knee
- Dislocated knee cap
Advice to the patients
- Wear sports shoes that offer the correct and proper support needed for you specific case
- Lose weight. Not surprisingly, being overweight will increase the stress on your joints and in particular on the knee joint.
- Don’t ignore the pain: an early diagnosis is key to prevent the degeneration of the knee joint.
- Keep moving, being sedentary might save you some pain in the short term but the long term outcome will be affected negatively by this.