10 Jul 2022

Understanding the knee's mechanics

From Sunday Morning, 10:45 am on 10 July 2022

Renowned orthopedic surgeon Kevin Stone, practising in San Francisco, is a proponent of fixing things before they get too bad, and that includes our knees.

Dr Stone tells Sunday Morning how avoiding injuries, or treating them as soon as possible, and arthritis are two main factors in maintaining knee health.


Knee Photo: Angelo Esslinger from Pixabay

Injuries often are the result of mental errors in judgment, especially for athletes, so getting rid of distractions can decrease the risk of injury, he says.

“Never workout watching the TV or reading a book, listening to music is okay.

“The reason is that … you need to listen to your body. You need to know when your heart rate is high. You need to know when you're starting to sweat, when your muscles are a little sore and be able to push past that barrier a little bit each time.

“If you're distracted … you're losing half the benefit of the workout that you're intending to do.”

Maintaining a range of motion in your knees helps prevent them from wearing out, he says, adding that squatting is a superb exercise with many benefits.

“Abnormal motion leads to abnormal wear, the same way a car tire on your car that's out of line wears out so fast.”

But if you do get hurt, then the sooner you obtain a diagnosis and repair it then the less chance of needing to interfere with the biologics of your joint, he says.

“On the other hand, if the tissues are badly damaged or a surgeon has already gone in and taken out the meniscus, we often would like to see that patient early and put the meniscus back in so we do lots of donor meniscus cartilages now to help restore the normal mechanics of the knee and protect the joint.”

His preference in treatments is to delay or minimise non-biological alterations as much as possible.

“We now have developed a number of techniques for both suturing and for adding growth factors and adding the body’s own progenitor cells to stimulate healing in areas where we didn't used to have that ability.”

For example, for early treatment of traumatic arthritis and osteoarthritis, they use oral supplements in addition to injections containing lubrication and growth factors to provide nutrition for the joints. 

“We take their platelets [from their blood] and get their growth factors from the platelets and when those are put into the joint with the hyaluronic acid, the lubricant, it stimulates the joint to produce more lubrication over time.

“So in the old days, we used to just inject the lubricant and people would get some relief for a few months. Now when we inject the lubricant with the growth factors, many people get six months to a year of joint relief, even in severely arthritic joints.”

In fact, he believes that many people who've been told that they need a knee replacement actually don't.

“Most of the time the bone on bone changes are only in one part of the knee and not all of the knee joint. And so if they're just in one part, our bias is to just resurface the one part that's worn out and not put someone through a full knee replacement.

“On the other hand, if they're bone on bone in multiple compartments, then we've really changed what knee replacement means. We now use robotics, robotic guidance, and a robot in the operating room which gives us so much more precision.

“It also permits us to get rid of the cement that used to be used to fix total knees in place, and it was the cement that always came loose overtime and surgeons used to tell their patients hey, go home and protect your knee.

“Well, now we tell patients go home and exercise and the more they exercise on their knee replacement that's done without cement, the stronger the bones become, the stronger the muscles become and the better they do.”