What is knee replacement surgery?Knee replacement surgery also known as knee arthroplasty, is a surgical procedure that replaces the weight-bearing surfaces of the knee joint which can become easily damaged due to pathologies such as osteoarthritis, rheumatoid arthritis or post-traumatic arthritis. The therapeutic goal of the procedure is to relieve pain and provide the knee joint with the stability it needs to bear the capacity of supporting the body’s weight given that movements at the knee joints are essential to many everyday activities such as walking, running, sitting and supporting the body in an upright position. 

Types of knee replacement surgery:

• Total knee replacement: is the most common procedure performed, it involves the replacement of both sides of the knee joint and lasts between one to three hours. It is a more aggressive procedure with a longer recovery time and an increase chance of developing scar tissue , but provides long-lasting relief and better mobility after.
• Partial knee replacement: involves the replacement of only  one side of the knee joint. It is a less aggressive procedure with a shorter recovery time, but it is not as long-lasting as a total replacement. 

Three common pathologies that may warrant a knee replacement surgery:

• Osteoarthritis: this type of arthritis is age related caused by the normal wear and tear of the knee joint. It produces inflammation, breakdown, and the gradual and eventual loss of cartilage in the joints which results in bones rubbing together. To compensate, the bones often grow thicker resulting in more friction and chronic pain. It mostly affects patients over 50 years, but younger people may be affected as well.
• Rheumatoid arthritis: this type of arthritis is an autoimmune disease that causes inflammation and thickness around the membranes of the knee joint which over time damages cartilage causing swelling, stiffness and pain.
• Post-traumatic arthritis: this type of arthritis is caused by cartilage damage resulting as a post sequela to severe or reperitive knee injuries such as fractures of surrounding bones of the knee or ligament tears.

Studies estimate that 90% of all knee replacements surgeries are due to late-stage osteoarthritis.

When is it time for knee replacement surgery?

Most doctors will try to exhaust all conservative treatment options before recommending any type of joint surgery. Some conservative treatments that may be able to control pain are: ice, heat, muscle stregthning exercises, physical therapy, lifestyle modification and/or pain medication such as NSAIDs and corticosteroid injections.

Surgery may be indicated when patients have been experiencing: long-lasting pain without improvement or that continues to worsen with conservative therapy; stiff and swollen knees over a long period of time with progressing pain at rest, especially at night; if the symptoms are beggining to interfere with daily activities such as walking, sleeping or going work; or if the pain is affecting the patient’s overall quality of life. In other words, patients seeking long-lasting relief for whom all others options have failed are ideal candidates for knee replacement surgery. 

Some contraindications for surgery are: weak thigh muscles that wouldn’t be able to support the new knee joint; having open sores or ulcers near the knee area which increases the risk of infection after surgery or if the patient is severely overweight due to the extra weight and pressure that would be applied on the knee which may cause shifting of the artificial knee components. 

What are the risks and complications?

Knee replacements have low complication rates. Possible complications include:

• Infection (lower than 2%)
• Developing a blood clot in the lower extremities known as Deep Vein Thrombosis (DVT)
• Developing a blood clot in the lungs known as Pulmonary embolism (PE)
• Risk of fractures during or after surgery
• Nerve damage leading to numbness or weakness
• Persistant pain or stiffness 
• Allergic reaction to the components of the artificial knee
• Excess bone formation around the artificial knee joint
• Excess scar tissue restricting movements at the knee
• Instability of the kneecap resulting in painful dislocation

What is the recovery time?

Most patients are able to stand and begin basic movements with recommended assistance devices (i.e. cane, crutches, walker) same day after surgery. The patient usually stays in the hospital for observation around 3 days. The first follow-up visit is after being discharcged from the hospital to asses motion and check the incision. The following weeks is the removal of stiches or staples at the doctor’s office. Returning to work depends on the physical demand of the job, it may be 6-8 weeks post surgery. If you are wondering when you will be able to drive, the answer is: after you are off pain medication.

After returning home it is recommended that patients see a physical therapist 2 to 3 times a week for at least 3 months to assist with exercises targeted to improve walking, regain motor function, and build strength. Therapy also avoids complications such as stiffness. Swelling and bruising after surgery is common and it will resolve with time. According to the American Association of Hip and Knee Surgeons, it can take up to 3 months to fully recover from a knee replacement, but it may take up to 1 year to know what the patient’s new baseline will be. In general, the majority of studies report satisfaction rates that average to 80%, where patients report significant pain relief and functionality. In 9 out of 10 people, artificial knee joints continue to work well over twenty years after the procedure was performed. There is no need to suffer from chronic. severe knee pain. 

Author Endrina Mangual Valladares MS3 Third year Medical Student at University of Medicine and Health Sciences (UMHS)