Knee Replacement Surgery

Knee Replacement Surgery

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Overview

Knee joint is the largest joint in the body. It is made up of the lower end of thigh bone (femur) and upper end of shin bone (tibia). The joint is covered with a small kneecap (patella). The articular structures are enclosed in a capsule and covered with ligaments and muscles. Menisci (C shaped structures) are located between the lower end of thigh bone and upper end of shin bone. Inner aspect of the capsule is lined by synovial lining which produces synovial fluid for joint lubrication. All these structures should work in harmony for perfect functioning of the knee joint. Disease or injury to any of these bony structures, muscles, ligaments or menisci will disrupt normal functioning of the knee joint.

What is knee replacement surgery?

It is a surgical procedure to remove damaged bone and cartilage for the knee joint and replace it with an artificial joint. Knee replacement is one of the most successfully performed orthopaedic surgery.

Why is knee replacement surgery done?

  • Consider visiting your doctor if you are an arthritic patient and have started experiencing severe knee pain even at rest.
  • Taking pain medications is no longer helpful and simple activities such as walking have become gruesome.
  • In case of severe injury to knee joint eg, sports injury or road traffic accident (RTA).
  • To correct leg deformity eg, bow knees (genu varum), lock knees (genu valgum)

How to prepare for knee replacement surgery?

Your doctor/ orthopedician will perform through evaluation of your signs and symptoms before proceeding with surgery.

  • Medical history- your doctor will question what all medications you are currently taking. In addition, if you have any pre-existing comorbidity such as diabetes mellitus, hypertension, thyroid disorder etc. In case of RTA or sports injury, the mechanism of injury is also closely studied.
  • Physical examination- next your doctor will perform a thorough physical examination and look for any kind of swelling, skin discoloration or tenderness around the knee joint. He/she will also assess the extent of deformity, strength and range of motion (ROM) of the knee joint.
  • Diagnostic tests- your doctor may advise you to undergo X-ray or MRI (magnetic resonance imaging) of the knee joint to determine extent of damage to the joint and surrounding soft tissue structures. Additional blood and urine tests may also be performed.

What treatment options are available?

After reviewing the results of your diagnostic tests (X-ray/ MRI, etc.), your doctor will have a detailed discussion with you regarding surgery. There are no age or weight restrictions for knee replacement surgery. Most patients are between 50 to 80 years of age. However, surgery has been successful in young and teenage patients as well. Your doctor will brief you about the procedure and its outcome. Never hesitate in asking any kind of questions to your doctor. The more you know, the more prepared you are both physically and mentally.

What are types of knee replacement surgery?

There are 3 different types of knee replacement surgery, namely-

  • Total knee replacement: also known as knee arthroplasty. In this type of surgery, the entire knee joint is replaced with an artificial joint.
  • Partial knee replacement: also known as unicompartmental knee replacement. In this type only the damaged and affected part of the knee joint is replaced. Patients who undergo this type of surgery spend less time in hospital and their recovery time is less in comparison to those who undergo total knee replacement. Because the surgery is done through a smaller incision there is less pain and less blood loss.
  • Bilateral knee replacement: as the name suggests in this type of surgery both knee joints are replaced at the same time.

What happens before knee replacement surgery?

  • Preoperative evaluation will be done by the orthopaedic surgeon a few weeks before the surgery is planned.
  • Review of medications will be performed and in case a patient is taking any blood thinning medicine, it will be discontinued.
  • Weight loss is recommended for obese patients.
  • Exercises to strengthen muscles around the knee joint should be performed preoperatively.
  • Blood tests, urinalysis, chest x ray, electrocardiogram (ECG), etc. should be performed as advised by the doctor.
  • In case the reports suggest any kind of infection, severe diabetes mellitus, high blood pressure, severe heart or lung disease or any other active metabolic disorder, then surgery is deferred until the condition is resolved.
  • Approximately 8 hours of fasting is required prior to surgery, preferably starting from midnight.

What happens during knee replacement surgery?

The surgery usually takes 1 to 2 hours. Your surgeon will start with giving anaesthesia. You may be given either general or spinal anaesthesia depending on your health status. The surgeon will make a cut over the kneecap to expose the joint. He/she will next remove the damaged part of the bone and cartilage and replace it with a prosthetic implant. The bony ends are replaced with metal implants and special plastic is used to replace the backside of the kneecap. Similar plastic material called spacer is placed between the two ends of metal implants to facilitate smooth joint movement. Special surgical cement is used to glue the artificial joint together. Cemented prosthesis are the most common type of artificial prosthetic knee joint. Uncemented prosthesis are not commonly used. However, sometimes a combination of the two is used. A drain may be placed to drain out fluid and prevent postoperative swelling around the joint. The incision site is closed with either stitches or surgical staples and covered with sterile dressing. Most patients stay in the hospital for a day or two after surgery.

What happens after knee replacement surgery?

After the surgery has been successfully performed, the patient is transferred to the hospital room. On waking up vitals (blood pressure, body temperature, pulse rate and respiratory rate) are taken. Wound is inspected and fresh dressing is applied. Drain is usually removed the next day. Pain medications are often prescribed for a short period of time. Next day the physiotherapist will start with an exercise program. Initially a continuous passive motion machine (CPM) is used to slowly bend the knee joint. The therapist will also assist you in taking a few steps with the help of a walker, crutches or cane. Hospital stay may vary from 2 days to a week.

You will be under close observation of your surgeon and physiotherapist for the next few days. Pain levels will be closely monitored and accordingly doses will be altered. The nursing staff will perform daily wound inspection. Your physiotherapist will encourage you to perform specific strengthening and range of motion exercises for the knee joint. Walking around for short distances is also encouraged. Try to use your knee as much as possible but do not overexert yourself.

What happens after discharge from hospital? (first 3 months)

Once back home you can resume your normal diet. You should drink plenty of fluids. Certain lifestyle modifications will ease your everyday activities such as, raised toilet seat, handrails in bathroom, hand held jet/shower spray, shower seat and high chair for sitting. It is also important to declutter your house and remove any unnecessary piece of furniture, wires in the walkway, loose rugs and door mats to avoid risk of falls. Always keep the floor of the bathroom dry and keep shampoos and soaps away on a stand. Avoid staircase use until recommended by your surgeon. You can also resume driving after consulting your surgeon.

Continue physiotherapy after discharge from hospital for at least 6 to 8 weeks. You will experience pain and stiffness post surgery but this should not stop you from exercising. Exercises should be performed under supervision and you can contact a physiotherapist for home visits.

  • Recovery beyond 3 to 6 months
  • Gradually you will regain strength and performing daily activities will be much easier. However, you still need to continue physiotherapy and can take regular appointments for the same. Regular walk is essential in maintaining knee joint mobility. Certain activities should always be avoided, such as
    • Knelling
    • Twisting the operated leg
    • Floor bending
    • Squatting
    • Lifting heavy weights
    • High impact activities such as, running, jogging, jumping
    • Contact sports such as, football, basketball
    • Prolonged sitting in a car while traveling
    The prosthetic joint is designed for everyday activities and performing any of the above-mentioned activities could lead to joint dislocation, which may require another surgery. Although you will be fully functional 6 months after surgery, regaining complete muscle strength around the knee joint may take around a year.

How long will the new joint last?

The artificial joint will last somewhere between 15 to 20 years depending on the type of artificial joint material used and usage. However, researchers have suggested that with recent advances over 82% of replacements are still functional after 25 years. In case the joint is dislocated or damaged, repeat surgery (knee revision surgery) has to be performed but this one is rather more complicated than the original surgery.

What are the complications of knee replacement surgery?

Most patients do not experience any complications after knee replacement surgery. However, few of them may encounter certain complications. Some of them are-

  • Infection
  • Blood clots
  • Allergy to metal implants
  • Joint dislocation
  • Wear and tear of implant
  • Nerve damage
  • Bleeding into knee joint
  • Severe knee stiffness

What are the warning signs to look out for after knee replacement surgery?

Any unusual signs or symptoms that you notice post surgery are termed as warning signs. These should not be ignored and you should inform your doctor right away. Major warning signs include-

  • High fever above 100°F or 37.8°C
  • Unusual swelling in calf, ankle and foot.
  • Extreme pain with both rest and activity.
  • Tingling or numbness down the leg
  • Foot drop
  • Sudden shortness of breath (dyspnea)
  • Pain and tenderness in calf muscles
  • Chest pain
  • Oozing of wound
  • Rupture of wound

Ignoring these warning signs increases the risk of complications.

Tips for speedy recovery

  • Surgical wounds should be kept dry for at least 2 weeks.
  • Keep your weight under check.
  • Elevate your leg while applying ice packs to reduce swelling.
  • Wearing compression stockings reduces the risk of developing blood clots.
  • Taking iron supplements will promote tissue healing.
  • Topical pain relieving gels/ointments should be preferred over oral pain medications.
  • Perform regular light exercises to maintain strength and mobility.
  • Regular walking for 20 to 30 minutes, at least 3 or 4 times a week.

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