Knee Replacement - An Overview

Knee replacement is increasingly being accepted as a suitable end-stage treatment for chronic knee pain and related disability. According to the ECAB clinical update orthopedic (Elsevier), more than 75,000 to 80,000 knee replacement surgeries are performed every year in India. Likewise, more than 6,00,000 knee replacement surgeries were performed in the United States in the year 2012 alone. According to the data collected by the American Academy of Orthopedic Surgeon, the number of knee replacement in the patients between the ages of 45-64 has tripled between 2000 and 2012; whereas it has increased by 95% for patients who were 65 years or above. While there are no age-related restrictions on knee replacement surgery, recent research carried out in Spain indicated that surgical replacement works best for the patients who are 65 years and above. The study also posits that a 45-year-old patient, who undergoes a knee replacement, may need another surgery during the lifetime because the implants typically last about 15 to 20 years.

A total knee replacement (tkr) is a surgical procedure which is performed to replace diseased knee with an artificial material or graft. The thighbone (or femur) joins the bone of the lower leg (tibia) at the knee joint. During the procedure, the end part of the thigh bone is removed and replaced with a metal graft. Similarly, the head or end part of the tibia is also removed and replaced with a channeled plastic piece with a metal stem. Depending on the condition of the kneecap of the joint, a plastic "button" may also be added to the kneecap surface. The artificial materials used in a total knee replacement (tkr) are called as the prosthesis.

When do you know if a knee replacement is needed? Helping a patient answer this question and get convinced about a real need for replacement involves taking multiple factors into consideration. An orthopedic surgeon can suggest you a proper treatment by interpreting the radiography images like X-ray, MRI, or ultrasound, and by taking the history of the symptoms. By interpreting the anterior-posterior view of the x-ray, the surgeon can determine the extent of damage in the knee. Osteoarthritis is known to be the leading cause of severe damage to the knee joint. However, other conditions like rheumatoid arthritis can also cause such symptoms.

Indications for Knee Replacement

Knee joint can be damaged in following conditions:

  • Severe osteoarthritis
  • Rheumatoid arthritis
  • Ligament damage or infection that leads to severe osteoarthritis
  • Gouty arthritis
  • Avascular necrosis (death of bone following loss of blood supply)
  • Bone dysplasias (abnormal growth of bone)
  • Certain tumours
  • Other joint infections
  • Post-traumatic arthritis
progressive damage of knees due to osteoarthritis

When is Knee Replacement Advised?

Diagnosis includes physical examination, symptomatology, radiography, blood tests, CT scan and MRI.

Radiological examination of the knee joint is the most valuable diagnostic tool. In Osteoarthritis, a plain x-ray of the knee joint shows the following features:

  • Loss of joint space (due to destruction of articular cartilage)
  • Sclerosis
  • Subchondral cysts
  • Osteophytes
  • Bony collapse
  • Loose bodies
  • Deformity and mal-alignment
x-ray image showing differnt stages of knee joint damage

History of Total Knee Replacement (TKR)

The total knee replacement or tkr surgery is one of the most popular orthopedic surgical procedures in the world for providing relief from chronic pain and disability caused by advanced arthritis of the knee or other joint disease conditions.

1968: First “Modern” Knee replacement surgery was performed in 1968. Since then improvements in surgical techniques and materials have greatly increased its effectiveness.

1970s: The total condylar knee arthroplasty was designed by Insall and colleagues in 1972 and is considered to mark the era of “modern” knee replacement.

1980s: Knee implant design became more sophisticated, and the concept of the cementless prosthesis was introduced.

1990s: Repicci introduced the concept of minimally invasive surgery in the early 1990s using the uni-condylar prosthesis.

2000-2015: Much advancement in surgical procedures and implants took place in this era such as minimally invasive surgery, gender-specific knees, and customized knees.

Knee ReplacementPastPresent
Operating time4-6 hours1.5 hour approx.
Recovery time6-9 months2-3 months
Blood transfusion3-4 units1 unit
PainModerate to severeMinimal
Range of motion90 degrees120-145 degrees
Permitted ADL (activities of daily living)Major restrictionsMostly allowed
Incision length20-25 cms10 cms
Hospital stay15-20 days4-5 days
Implant Lifespan8-10 years15-20 years
Above estimates can vary based on specific medical condition and other factors.

Types and Techniques

Diagram of Knee replacement surgery types

A knee replacement surgery is a complex procedure that requires an orthopedic surgeon to make precise measurements and skillfully remove the diseased parts of your bone and to shape the remaining bone to accommodate the knee implant. During the surgery, the surgeon fixes the artificial knee components. There are two types of replacement surgeries:

Types of Knee Replacement

Total knee replacement (TKR)

In total knee replacement surgery, also referred to as TKR or TKA, the surgeon replaces an arthritic knee with an artificial metal or plastic parts called the 'prostheses.' The aim of this procedure is to relieve pain and restore a sense of normal function and mobility to damaged joint.

Partial Knee Replacement (PKR)

Partial Knee Replacement which is also referred to as Unicondylar, PKA or PKR, is done for patients whose arthritis is limited to one side of the knee joint. It may be done through a tiny incision, and a recovery is usually much quicker than that seen in the case of total knee replacement (tkr).

Techniques for Knee Replacement

Traditional knee replacement

In this procedure, the surgeon makes an 8-12 inch incision and operates on the knee using the standard surgical technique. The incision (surgical cut) is made along the front and toward the middle or along the front and to the side of the knee joint. Traditional tkr procedure usually involves cutting into the quadriceps tendon to turn the kneecap over and expose the arthritic joint. This method typically requires 3 to 5 recovery days in the hospital and about 12 weeks of recovery time.

Minimally Invasive TKR

Nowadays, the surgeons prefer a technique called minimally invasive surgery, where the procedure requires the incisions of only 3-5 inches or even smaller. As the incision is smaller than the open technique, it causes less pain, lower soft tissue damage and leads to a shorter recovery time. However, in some cases, minimally invasive technique can present some challenges as it does not allow a surgeon to have a full and easy view of the site.

Robotic-assisted TKR

A robotic-assisted surgical technique helps the surgeon to plan and execute steps such as the bone cutting with the aid of a computer, that which has access to your exact joint anatomy and condition. The quoted advantage include a shorter stay, quicker recovery and better fit of the implant.

MRI- guided custom TKR

It is a new technology in which 3D images enable the surgeon to choose precisely the exact size of implant and plan the precise location of the components based on each patient’s particular joint anatomy and the associated arthritic changes.

This enables the doctor to determine the appropriate size better of the implants and to align them more accurately, potentially leading to better outcomes for his valued clients. Other benefits to the patient include smaller incisions, less bleeding, less actual surgery time and faster rehabilitation.


It is an advanced surgical guidance system designed to improve accuracy and alignment in total knee replacement (tkr). Zimmer iASSIST Knee allows the surgeon to verify each surgical step, such as bone cuts and overall alignment, in real time, reducing mechanical errors during tkr.

Joint Preserving TKR

The joint preserving techniques allow the surgeon to affix the implant without removing the soft-tissue components such as the posterior cruciate ligament (PCL), or ACL. These techniques are very new and claim a superior joint motion and a closer to natural knee movement.

Implant Types

“There are multiple types of knee implants that surgeon and patient can discuss before selecting the best option. The selection is often based on a patient’s condition and lifestyle, and surgeon's own expertise with a particular implant type.”

Fixed bearing

The fixed-bearing implant is the most common knee replacement implant. In this implant, the Plastic (polyethylene cushion) of the tibial component is attached firmly to the metal platform base. The femoral component then moves over this cushion.

The fixed-bearing implants provide an excellent ROM (range of motion) and are just as durable as other implants for most patients.

Mobile bearing

It allows the plastic cushion of the tibial component to rotate, giving patients greater flexibility on the medial and lateral sides of the knee joint. These implants work well for young and active patients.

Medial pivot

This implant replicates the natural function of the knee. It rotates, twists, bends, and flexes like a natural knee joint.

Gender specific

Some studies have indicated that the shape of the woman's knees differs from men. Moreover, it is not just a size difference. Although traditional knee replacements are available in different sizes, gender-based implants are specific to female anatomy.


A customized knee implant is created and developed based on the MRI of the joint to account for the differences in the anatomy from patient to patient. The claimed advantages include a better fit and alignment, and a more natural feel to the artificial knee.

Knee Replacement Manufacturers

Many device companies are designing and manufacturing knee implants, which are made from a variety of metal, plastic, and ceramic components.

Artificial knee joints consist of 3 components:
  1. Femoral component (metal)
  2. Tibial component (metal and plastic)
  3. Patellar or knee component (plastic)

Whether the patient can have a total knee replacement (tkr) or partial knee replacement (pkr), the difference depends on the patient’s age, condition and activity levels. These are the world's top most companies which design and manufacture artificial knee implants:

  • Zimmer
  • Smith & Nephew
  • Stryker
  • Biomet
  • Wright
  • DePuy - a division of J&J

Above information about the techniques and implants is to educate about various choices, However, in the end, it is important to spend adequate time with your doctor to select the right implant and technique. As it natural that a particular doctor with expertise in one technique or implant will lean towards it, you can also seek a medical opinion from other experts to help make a sound decision.

Knee Replacement Complications:

Most knee replacement operations are risk-free but about one to two percent cases may have a few complications. As a result of many advances in the surgery techniques, most of these complications are not very severe and can be treated successfully.

The risk of complications depends on some factors including age and general health of the patient. The possible complications are:

  • Joints swelling
  • Debilitating pain
  • Damage to surrounding tissues, arteries or ligaments
  • Nerve damage
  • Fractures
  • Unstable implants
  • Limited range of motion (ROM)
  • Problems standing or walking
  • Blood clots, deep vein thrombosis, pulmonary embolism
  • Allergic reaction
  • Infections

In rare cases, serious complications may require a knee revision surgery, which can be expensive, painful, and inconvenient. Patients, who are older, are obese or have diabetes, are at increased risk of developing some of these complications.

Physiotherapy after Knee Replacement Surgery

Physiotherapy treatment is an essential part to hasten the healing process and ensure a satisfactory outcome in all the patients following a knee replacement. It should ideally begin even before the surgery.

The treatment may consist of:

  • Electrotherapy
  • The use of crutches
  • The use of a compression support
  • Joint mobilization
  • Hydrotherapy
  • Cryotherapy
  • Progressive exercises to improve flexibility, strength (especially the quadriceps muscle)
  • Awareness development
  • Biomechanical correction
  • Exercise therapy
physiotherapy after knee replacement surgery
electrotherapy after knee replacement surgery

Physiotherapy Exercises

Typically, the subsequent exercises are recommended shortly after the knee replacement. These must be done under the strict supervision of a trained physiotherapist only. You may feel uncomfortable initially, but these exercises can speed up your recovery and diminish your surgical pain.

Quadriceps Sets:

  • Tighten your thigh muscle.
  • Try and straighten your knee.
  • Hold for five to ten seconds.
  • Repeat this exercise about ten times throughout for a 2-minute duration.
  • Rest one minute and repeat.
  • Continue till your thigh feels fatigued.

Straight Leg Raises:

  • Raise your leg several inches.
  • Hold for 5 to 10 seconds. Slowly lower it.
  • Repeat till your thigh feels fatigued.
  • You can also do it while sitting.
  • Fully tighten your thigh muscle and hold your knee straightened together with your leg unsupported.
  • Continue these exercises sporadically till full strength returns to your thigh.
straight leg raise exercise

Ankle Pumps:

  • Move your leg up and down rhythmically by acquiring the calf and shin muscles.
  • Perform this exercise sporadically from 2 to a few minutes.
  • Repeat 2 or 3 times every hour in the hospital room.
  • Continue these exercises till you feel fully recovered and the lower-leg swelling is subsided.
ankle exercise afer knee surgery

Knee Straightening Exercises:

  • Try to straighten your knee and touch the rear of your knee to the bed.
  • Hold the position for 5 to 10 seconds.
  • Repeat till your thigh feels fatigued.
knee straightening exercise

Bed-Supported Knee Bends:

  • Bend your knee as much as possible so that your slippers touch the bed.
  • Repeat many times till your leg feels fatigued or till you are barely able to bend your knee.
Knee bends exercise with support

Sitting Supported Knee Bends:

  • Place your foot behind the heel of your operated knee for support, while sitting at bedside or in a chair with your thigh supported.
  • Then, slowly bend your knee as much as possible.
  • Hold the knee in the position for 5-10 seconds.
  • Repeat the exercise several times until your leg feels fatigued or you can completely bend the knee.
Knee bends exercise in sitting position

Sitting Unsupported Knee Bends:

  • Sit at bedside or in a chair with your thigh supported
  • Bend your knee as much as you can till your foot rests on the floor.
  • Now, the foot resting on the floor lightly, slide your upper body in the forward direction in the chair to increase the knee bend.
  • Hold it for 5-10 seconds.
  • Now, straighten the knee fully.
  • Repeat the exercise several times until your legs are fatigued, or you can fully bend your knee.
Knee bends exercise without support

Activities After Knee Replacement:

  • Self-assisted slow passive flexion of the knee should be started.
  • The range of knee flexion should be less than 40 degrees during the first three days.
  • After 4th or 5th day of the surgery, the patient is allowed to stand and ambulate with walkers.
  • You can now begin walking for short distances in your hospital room but with assistance.
  • Isometric exercises are to be done between 7 to 14 days.
  • Exercises of active range of motion.
  • Knee flexion should be 90 degrees.
  • Straight leg raising (SLR) is also effective.
  • Partial weight bearing ambulation is started on crutches.
  • Walk as steady and smooth as you can.
  • Adjust the length of your step and speed as necessary to walk.
  • As your muscle strength improves, you may spend more time on walking.
  • You can gradually put more weight on your leg.
  • walking with crutches after knee replacement surgery
    walking without support after knee surgery

    Stair Climbing and Descending

    Climbing stairs require strength and mobility. Take a support while doing so, and take one step at a time.

    Success ratio after knee replacement

  • Approximately 85% of the patients, who have a knee replacement, experience less pain and improved mobility.
  • Recovery varies from patient to patient. Typically, the rehabilitation period lasts for 6-12 months or longer.
  • Always remember that an artificial knee joint will not function the same as a normal knee.
  • In the case of severe knee injuries with subsequent weakness or knee stiffness before the surgery or in those, who have other surgical complications, the rehabilitation may be required for an extended period.
  • After the surgery, the patients who do not take rest properly from the stressful activities, or those who do not perform exercises, may have longer recovery time.
  • It is always advisable to have a second opinion before undergoing knee replacement surgery.

    Last Updated: December 22, 2016