The procedure by which a damaged knee joint is replaced with an artificial material is termed as total knee replacement. The longest bone of the human body, femur meets the lower leg (tibia) at the knee joint. During surgery, the damaged cartilage and bone are removed from the knee joint. The thigh and calf bones are joined with metal implants at their ends. A plastic material is inserted in the middle of the metal implant which allows smooth movement of the knee joint. In between the metal implants, a plastic gaper is introduced which aids in free movement of the joints.
Causes of knee replacement surgery
- Many middle-aged and elderly people suffer from Osteoarthritis which is also known as degenerative joint disease, and this is the most important cause of knee replacement surgery
- Deficiency of Vitamin D and Calcium in the blood can also lead to joint disease.
- Other conditions that cause knee damage include rheumatoid arthritis, which causes inflammation of the synovial fluid.
- Arthritis due to trauma or an injury may also cause damage to the cartilage of the knee.
The main purpose of knee replacement surgery is to relieve intolerable that cannot be reduced by any other treatment.
Structure of the knee
Joint is the meeting point of two bones held together by muscles, ligaments, and tendons. Joints are further covered by a layer of tissue called cartilage which absorbs shock and protects the joint. Knee is a movable joint at the lower part of the body which allows movement of the legs.
The quadriceps muscles which are situated at the upper end of the thighs helps in straightening the legs and the hamstring muscles, situated behind the thighs helps in bending the legs at the knee joint.
The ligaments also aid in movement around the knee. Some of them protect the knee joint, whereas, others limit the movement of the shin bone ( tibia).
Components of the Knee
- Tibia (shin bone): This is the larger bone of the lower leg.
- Femur (thigh bone). This is the upper leg bone and also the longest bone of the human body pain which does not subside even after resting or taking medications.
- Patella. This is the knee cap.
- Synovial membrane. This is the tissue covering the knee joint which adheres it into a joint capsule. Synovial fluid, a secretion of the synovial membrane, prevents acts as a lubricating surface and protects the joint from friction.
- Ligaments and Tendons: These are hard, elastic connective tissues that aids in movement of the knee joint.
- Meniscus: A cartilaginous part of the knee joint which acts as a shock absorber
Why Knee Replacement Surgery is done?
It is very difficult to predict which patients will require knee replacement surgery and which patients will be treated merely by medicines. Even though sometimes, this surgery remains the only option left for treating this acute pain, doctors age, past medical history, kind of treatment he is undertaking, obesity and other nutritional cannot do this surgery due to a lot of complications and side effects. Many a times, the patient’s deficiency and diseases makes it difficult to perform the operation. If severe knee pain characterized by chills , uneasiness in stretching and bending legs, difficulty in walking, running, lifting weights and other activities makes life difficult and the pain does not subside by taking pain relievers and analgesics, this surgery remains the only solution.
Potential risks associated with the surgery
The main risk associated with total knee replacement includes blood clots that can occur at the site of surgery and can travel to the lungs (pulmonary embolism). Pulmonary embolism can cause pain in the chest while breathing, light headedness or low oxygen in the body, palpitations, dry cough etc. They can rarely cause death too. Other risks include urinary tract infection, nausea and vomiting (usually related to pain killers), chronic knee pain and stiffness, bleeding into the knee joint, nerve damage, blood vessel injury, and sometimes even re-surgery has to be done due to infection in the knee. In addition to these, the risks of anesthesia include potential heart, lung, kidney, and liver damage.
Knee Replacement Surgery: The Procedure
1. Before the surgery
- Before the surgery the doctor will guide the patients about the necessary advantages and disadvantages of this type of surgery.
- The patient is asked to sign a consent form prior to the operation.
- A complete medical history of the patient is recorded and necessary diagnostic tests like complete blood hemogram, liver function, test, renal function test, allergy tests, diabetes etc are performed to rule out unnecessary complications after the surgery.
- The patient must inform the doctor about all the previous medications he is undertaking and whether he is allergic to any particular group of medicines
- If the patient is undertaking any blood thinning medications like heparin, aspirin or any other medicine that affects blood clotting, that needs to be reported to the doctor and in most cases the intake of such medicines is stopped prior to the surgery.
- Fasting 7 to 8 hours before the surgery is a must some patients might have to be given sedatives to induce sleep before the surgery.
2. During the surgery
Since the surgery is a complicated one, it involves hospital stay for quite some time after the operation. In most cases the patient is subjected to general anesthesia, so that the operation takes place when the patient is sleeping. The surgery occurs in the following ways
- The patient is given a hospital gown to wear prior to the surgery.
- An intravenous (IV) route is started at the arms or hands 3-4 hours before the surgery so that the patient can be subjected to electrolytes and medications just after the surgery.
- A catheter is inserted at the urethra
- Heart rate, pulse rate, respiratory rate, blood oxygen level are constantly monitored during the surgery.
- The doctor first cleans the area around the knee with antiseptic lotion and makes incision at the knee area.
- The damaged portions of the knee are then removed and replaced with metallic or plastic prosthesis. Cemented and uncemented, both types of prostheses are used in the replacement of the knee joint. Three components make up the prosthesis: the tibial component, which replaces the shin bone, the femoral component, that replaces the end of the femur and patellar component that replace the bottom of the knee cap.
- The incision is stapled or stitched
- Excess fluid around the site of the incision may be drained out.
- The surgical site is covered with sterile bandage
3. After the surgery
Care at the hospital
- Post operation the patient is taken from the operation theatre to the recovery room where the vital organs of the patient are monitored for some time. Once the condition is stable the patient is sent to the hospital room. Since this surgery involves hospital for a long time, moving the replaced joint starts in the hospital itself under the guidance of doctors, nurses and physiotherapist.
- Splints attached to the knees can help in the easy movement of legs.
- A special type of machine called Continuous Passive Motion (CPM) machine has made life quite easier after shoulder joint replacement or knee replacement surgery. This machine is joined to the operated leg and it automatically makes the patient rotate its leg at various angles without putting any stress or strain at the site of surgery. Patients can gradually start walking on their own using crutches, walkers, canes etc.
Care at the home
- As advised by the doctor, the surgical area might have to be kept dry and regular dressing needs to be done once the patient reaches home.
- To reduce pain at the surgical site the doctor might ask to apply ice pack and pain relievers will be continued for a long time depending on the intensity of the pain.
- Any sign of redness, swelling, itching, pus coming out from the surgical site, pain with high fever and chills should immediately be notified to the doctor.
It must be kept in mind that a full recovery after the knee replacement surgery may take several months. So patients should avoid strenuous activities like running, climbing, bending around the knee, lifting heavy weights which can damage the replaced knee. One important thing is since the patients will find it difficult to walk for the first few days after surgery; they should take help of others to avoid falling down, as a heavy fall can completely damage the replaced knee. They also use walkers, canes or crutches to avoid fall.