Livestrong.com reports on why your knees weaken with age and what to do about it in an interview with Ashley V. Austin, MD, primary sports medicine physician at HSS. 

Over the years, everyday wear and tear can do a number on your cartilage. And when it withers, your knees will grow weaker. "As cartilage deteriorates, we have less cushion and support within our joint," Dr. Austin said. Without healthy cartilage to bolster your knees, they won't be as robust or function as well as they used to in your younger years. And as a result, "we have to rely more on the surrounding and supporting muscle groups to keep heavy loading forces off of the joint," Dr. Austin explained. But over time, these compensations can lead to other issues like muscle imbalances and, eventually, even injury.

“Regular exercise and strength training of the lower body (with a concentration on strengthening the hips) can help,” Dr. Austin said. “The hip muscles are some of our strongest muscle groups, and they help with changes in balance and gait that can happen with cartilage wear.”

"Muscle atrophy happens as we age. When we are younger, we can complete activities even if all of our supportive muscles are not activating at once. But with advanced age, our strength decreases." said Dr. Austin. 

“As the muscles that surround your knee weaken, they no longer have the capacity to support the joint. Not only does this equate to more stress on the knees, but it also lowers the threshold for injury,” continued Dr. Austin.‌

To maintain good muscle recruitment and activation, “your muscle support system needs to be more and more efficient to prevent injury the older you get. Therefore, it is imperative that we keep exercising and strength training throughout life to counter these changes and to prevent injury," advised Dr. Austin. 

Read the full article at Livestrong.com.