Media mogul Oprah Winfrey doesn’t want to take her knees for granted ever again. 

Winfrey revealed this week that she underwent right and left knee replacements last year. 

She shared this revelation during a recent "The Life You Want" class on gratitude. 

"My appreciation for every organ and every limb has just expanded exponentially," the 68-year-old told the class.

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She's now motivating others to be sure not to take their bodies for granted — and also to learn more about knee replacements.

Since the first knee replacement surgery was performed in 1968, medical advances have greatly improved the effectiveness of the procedure, according to the American Academy of Orthopaedic Surgeons (AAOS).

Entertainer Oprah Winfrey

Oprah Winfrey revealed this week that she had knee replacement surgery last year. "My appreciation for every organ and every limb has just expanded exponentially," she told a class entitled "The Life You Want."  (Reuters)

Approximately 754,000 knee replacements were performed in the United States in 2017, according to the Agency for Healthcare Research and Quality. 

Another source — Personalized Orthopedics of the Palm Beaches — puts that number at roughly 800,000 per year right now, and says the need and desire for the procedure is expected to grow. 

What should I know about the knees?

The knee is the largest joint in the body — and a healthy knee is vital to performing most daily activities, according to AAOS.

The knee consists of three bones: the lower end of the femur, or thighbone; the upper end of the tibia, or shinbone; and the kneecap, also known as the patella.  

When all components perform together "in harmony," the knee works normally. But when a knee injury or an underlying disease affects the harmony, patients complain of knee issues. 

Cartilage helps protect the bones that make up the knee joint so that they can move easily within the joint, while ligaments help keep the femur and tibia together for stability. 

To prevent the femur and tibia from rubbing against each other, "shock absorbers" help cushion the knee as we move. They are shaped like "C-shaped wedges" and known as menisci.

Arthritis Knee

Hips and knees are the most frequent culprits of arthritis, experts say. (iStock)

"All remaining surfaces of the knee are covered by a thin lining called the synovial membrane," per the AAOS.

"This membrane releases a fluid that lubricates the cartilage, reducing friction to nearly zero in a healthy knee."

When all the knee components perform together "in harmony," the knee works normally, AAOS noted on its website. But when a knee injury or an underlying disease affects this harmony, patients complain of knee issues. 

Why do some people need knee replacements?

Arthritis is the most common cause of chronic knee pain and disability, according to the AAOS. 

As people get older, the cartilage that protects the knee can wear down, which can eventually cause the bones to rub directly against each other — causing pain. 

Chronic inflammation eventually leads to cartilage damage.

This is often known as the "wear-and-tear disease," or osteoarthritis.

Another type of arthritis that can cause knee pain is rheumatoid arthritis. It's an inflammatory disease in which the synovial membrane that surrounds the joint becomes inflamed. 

The chronic inflammation eventually leads to cartilage damage.

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A third type of arthritis is called post-traumatic arthritis from a serious knee injury. It's when bone fractures or ligament tears lead to cartilage damage over time, eventually causing knee pain and limiting the range of motion of the knee.

What is a knee replacement?

"A knee replacement (also called knee arthroplasty) might be more accurately termed a knee ‘resurfacing’ because only the surface of the bones are replaced," according to the AAOS.

They are four general steps for a knee replacement procedure.

Oprah Winfrey, entrepreneur

When Oprah Winfrey first returned home after her procedure, she revealed that she could not lift her leg. "I couldn't lift my heel off the bed," she said during a class on gratitude.  (Getty Images)

The step is removing the damaged cartilage surfaces (along with some bone) at the ends of the femur and tibia.

The second step is replacing these surfaces with metal components to recreate the joint. Sometimes the metal parts may be "cemented or press fit" into the bone.

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Then the undersurface of the kneecap is cut — and depending on the case, some surgeons will resurface with a "plastic button." 

Lastly, a plastic spacer is placed between the metal parts to create a smooth surface so that the knee joint glides easily when we move.

What is a minimally invasive total knee replacement?

The traditional surgical approach to a knee replacement involves a long vertical incision in the center of the knee to expose the joint, according to AAOS.

"It is common to feel a lot of muscle soreness and sometimes weakness right after the operation, but this usually improves after a few days or weeks."

Minimally invasive total knee replacement uses a shorter incision and a less-invasive technique to access the joint to reduce pain after surgery — and to have a faster recovery, per the association.

But the minimal invasive approach is not suitable for all patients. 

What is the recovery from this procedure like?

"It is common to feel a lot of muscle soreness and sometimes weakness right after the operation, but this usually improves after a few days or weeks," said Dr. Claudette Lajam, professor of orthopedic surgery at NYU Langone Grossman School of Medicine in New York City.

Winfrey noted she first had a knee surgery in August of last year — then another surgery on the opposite knee in November of last year. 

"Most surgeons like to space the knee replacements at least three months between the surgeries," said Lajam, who is also a spokesperson for the American Academy of Orthopaedic Surgeons.

Dr. Lajam told Fox News Digital that having at least a three-month interval between surgeries allows the patient to recover adequately before undergoing the second procedure. 

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"Complete healing takes more than a year, but a good portion of the healing after knee replacement is done in about three months," added Lajam.

The pain that patients feel after the procedure can be "substantial after the operation until the legs adjust to being straightened."

"For bilateral simultaneous knee replacements — when both knees are done in the same operation — I told folks to expect about four months before they start to feel normal again and have their energy back."

When Winfrey first returned home after her procedure, she said she could not lift her leg. 

Opray Winfrey with glasses

Oprah said she vowed that if she "was ever able to get up, walk around and move again — that I would take advantage of movement, exercise and of being able to be fully in my body," she told a class. (Reuters)

"I couldn’t lift my heel off the bed, and I vowed if I was ever able to get up, walk around and move again — that I would take advantage of movement, exercise and of being able to be fully in my body," Winfrey told the class.

Lajam noted that a patient’s recovery depends on the state of the knees before the operation. 

"For folks who have severe deformities like bowlegged or knock-kneed legs, sometimes muscle soreness can persist for many months," she said. 

Pain can be ‘substantial’

The pain that patients feel after the procedure can be "substantial after the operation until the legs adjust to being straightened," Lajam told Fox News Digital.

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Lajam noted that while pain after a single knee replacement can be "substantial, we have gotten much better with the anesthetic techniques and nerve blocks to help with immediate postoperative discomfort."

She noted the use of a medication called tranexamic acid around the time of the operation helps control bleeding, which in turn can help with pain.

patient after surgery

Today, "modern techniques allow pain to be better controlled" after knee surgery, "especially in the first couple of weeks after the operation." (iStock)

"In general, modern techniques allow pain to be better controlled, especially in the first couple of weeks after the operation," she added.

"With modern opioid-sparing pain protocols, we can manage postoperative pain fairly well."

For example, in her practice, this means not only employing pain medication, but also using cold therapy, reminding patients to elevate their leg and sometimes employing "negative pressure dressings over the incisions to help decrease swelling and manage pain."

What are the complications?

Complications are not common after a knee surgery.

Serious complications such as a joint knee infection occur in less than 2% of patients — while a heart attack or stroke occurs even less frequently, according to the AAOS.

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Blood clots in the leg veins are one of the most common complications of knee replacement surgery. The clots can be life-threatening if they travel to the lungs; after surgery, patients are counseled on how to prevent blood clots.

This may include elevating the legs, doing leg exercises to increase circulation, wearing support stockings and taking special medication to thin the blood. 

Other complications include problems with the implants inserted during the procedure, which can loosen after surgery. 

Always define ‘hike’ before you do it

"As I was rehabilitating, I started hiking. Every day, I tried to hike more and do more," Winfrey said. 

But not everyone shares her definition of "hike."

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Joseph Zambrano, Winfrey’s social media director, recently lamented on TikTok while sporting non-hiking gear how the former talk show host "tricked" him — along with her good friends Gayle King and Ava DuVernay — into going on a hike.

"You know, I think people should be honest when they say, ‘Let’s go on a hike,’" Zambrano said on TikTok. 

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"She said it was five to seven minutes. It’s been five to seven miles."

He posted, "I’m never going on a hike with Oprah ever again."