Total Knee Arthroplasty: Indications and Complications

The knee joint is a hinge joint comprising three bones, femur (thigh bone), tibia (shin bone) and the patella (knee cap). The lower surface of femur and upper end of tibia is covered with cartilage. The cartilage in turn is covered by a synovial membrane that produces synovial fluid which helps in reduction of friction. Menisci are crescent shaped wedges present between the tibia and femur. Multiple ligaments present inside and around this joint provide it with stability while the surrounding muscles provide strength to the knee joint. Conditions like osteoarthritisand rheumatoid arthritis may lead to chronic knee pain which interferes in the normal daily functioning. When medical and physical rehabilitation aren’t able to provide relief from symptoms your doctor might refer you to an orthopaedic surgeon for total knee arthroplasty. Annually 600,00 Americans undergo this procedure.

Procedure of Total Knee Arthroplasty

On the day of the surgery you will be admitted to the hospital. The anaesthesia team will evaluate you and with their input help you decide the type of anaesthesia to be used for the surgery. The surgery can be done under general, epidural, or regional block anaesthesia. After the effect of anaesthesia sets in your surgeon will proceed to remove the damaged cartilage and a small amount of bone from the affected knee joint. The damaged cartilage and bone is replaced with a metal prosthesis that mimics the joint surface. Depending upon the type of prosthesis it is cemented or ‘press fit’ into the bone. A plastic spacer is introduced between the metallic surfaces to ensure smooth movement. The patella may or may not be resurfaced.

Indications for Total Knee Arthroplasty

Many conditions lead to chronic knee pain leading to difficulty in performing normal day to day activities. These include:

• Osteoarthritis
• Rheumatoid arthritis
• Arthritis following fracture.

Amongst patients suffering from these conditions total knee arthroplasty is recommended for individuals with:

• Failure to improve on medical and physical therapy
• Deformity of the knee
• Pain in the knee while resting
• Severe knee pain which interferes with daily activity
• Inflammation of the joint that doesn’t improve with medication or rest.

Preparation for Total Knee Arthroplasty

Preparing for a total knee arthroplasty will require multiple tests and possible lifestyle changes to ensure a swift recovery and reduction in long term complications following the surgery.

• Your doctor will like to record your medical history and perform a thorough physical examination to assess the mobility, strength and alignment of the affected joint.
• An x-ray, CT scan or/and a MRI may be ordered to determine the extent of disease in the affected joint.
• Inform your doctor about all the medications and herbal supplements that you are consuming. You might be asked to stop some of them before the surgery.
• If you have a heart disease you will be required to get a clearance from a cardiologist before you can undergo the surgery
• Bacteria, when present in the blood stream, can colonise the implant and lead to complications.
• Routine blood and urine investigations will be requested to look for infections. In patients with a urinary tract infection, medications are prescribed to treat the condition. Older men with enlarged prostate are required to undergo treatment for it before the total hip arthroplasty.
• Dental procedure can also lead to introduction of bacteria into the blood stream; hence major dental procedures should be completed before the surgery.
• Multiple changes will be required in your home to help you during your recovery
• A secure handrail, stable chair and long handed sponge or shower hose in your bathing space
• Secure handrail by the staircase
• Remove loose electric cords and loose carpets from the area where you will be walking to reduce the risk of tripping over them
• Stable chair with firm pillows, at the height of 18-20 inches, and stable arm rest and footstool for intermittent leg raising
• Raised toilet seat.

Complications of Total Knee Arthroplasty

Total knee arthroplasty is a relatively safe procedure, with serious complications seen only in 2% of patients. The complications encountered are:

• Infection at the site of surgery or in the prosthesis
• Blood clot formation in the leg, this clot may dislodge from the leg and travel to the lung, heart or rarely the brain. Administration of blood thinning medications, early mobilisation, ankle pump exercise and support hose help in reducing this risk.
• Wear down of implant. In some individuals scarring may occur leading to a limited range of motion after the surgery
• Injury to nerve
• Injury to blood vessel
• Continuous pain in encountered in a small population of individuals who have undergone total knee arthroplasty.

Recovery from Total Knee Arthroplasty

Following the surgery you will be constantly monitored during your stay in the hospital. Multiple measures will be taken to reduce the risk of formation of blood clots in your leg. These measures are

• Blood thinning medications will be prescribed for a few weeks to reduce the risk of blood clot
• Few hours post surgery you will be encouraged to start walking with the help of crutches or a walker
• Ankle pump exercise, inflatable leg covering to prevent stasis of blood in the lower limbs.

You will be staying in the hospital for a few days after the surgery. Before you are discharged from the hospital you will be taught several exercises to restore movement and strengthen your knee joint. It is essential that you perform these exercise two to three times a day, for a few weeks at your home. To restore motion you will be advised to use a machine called Continuous Passive Motion (CPM) exercise machine; it passively moves your knee while you are at rest. You will be advised to slowly increase your mobility. Most patients are able to resume light daily activity in 3-6 weeks after the surgery. Driving can be resumed after you are able to bend your knee enough to sit in a car, and have regained enough muscle control to use the brake and accelerator with an adequate reaction time; this generally happens 4-6 weeks after the surgery. It is essential to keep the wound clean and dry until it heals.

Contact your doctor immediately in you experience any of the following symptoms:

• Swelling, tenderness and redness in your calf or thigh- a sign of blood clot in your leg
• Sudden shortness of breath accompanied by localised chest pain- a sign of pulmonary embolism
• High fever with chills; redness, pain, swelling and discharge from hip wound-sign of infection.

Resources

• American academy of orthopaedic surgeon guidelines