So that you spent the weekend getting stuff accomplished—scrubbing the flooring, serving to a buddy transfer—or clearing your thoughts with a hike or bike trip. Come Monday morning, what’s your reward? A pair of achy knees.

When you’ve been noticing this an increasing number of, it’s not your creativeness: As you cross into your third decade and past, adjustments in your physique and life-style make your joints extra liable to that sort of discomfort. The truth is, as you enter the “messy center” of life, “it’s extra unusual for those who don’t have some sort of ache in your knees,” Joe Malizia, DPT, CSCS, a bodily therapist at HSS Sports activities Rehabilitation and Efficiency West Aspect in New York, tells SELF. That doesn’t imply it’s inevitable, although. A fortunate few individuals do attain their 90s with no proof of arthritis or different knee issues, orthopedic surgeon Nikkole Haines, MD, assistant professor at Penn State Bone and Joint Institute, tells SELF.

Whereas a number of the threat elements for aching joints are genetic, systemic, or in any other case exterior your management, there’s nonetheless lots you are able to do to beat back the kinds of issues that pop up with age and handle them once they happen. Right here’s easy methods to inform the distinction between somewhat age-related stiffness and swelling and one thing that’s extra critical—plus what to do about it.

Right here’s why your knees could be aching within the first place.

You’d count on to get up with some achiness after squatting heavy, mountaineering a brand new technical path, or climbing all 86 flights of the Empire State Constructing. However when discomfort begins to come up from, properly, easy common exercise, that may make you actually begin to surprise what’s happening.

All of it comes right down to adjustments in tissue in and round your knee. This may begin many years earlier than osteoarthritis—a situation that happens when the cartilage inside your joints breaks down over time—which tends to set in round your 50s and 60s.

Muscle mass decreases by about three to eight % per decade starting in your 30s, and its high quality begins to alter too, Dr. Malizia says. “After we’re younger, muscle is sort of a good filet mignon; it’s supple, it strikes very well,” he says—all of which helps assist and transfer your knee joint. However because the years cross, your muscle tissue are inclined to lose pliability and suppleness, which might translate into additional stress on the joint, even throughout on a regular basis actions.

Ligaments and tendons maintain your knee joint collectively, and people additionally are inclined to stiffen and tighten with age. That may compress the joint, inflicting ache or swelling, Dr. Malizia says.

All of those adjustments are compounded by every particular person’s asymmetries and distinctive motion patterns, the consequences of which add up over time. As an example, for those who all the time shift your weight to the precise whenever you’re standing, the muscle tissue and ligaments on that facet can tighten, pulling your kneecap ever-so-slightly off monitor in a method that may create irritation beneath. So whenever you add somewhat additional exercise to a knee that’s already barely irritated—possibly so barely you don’t even notice it but—you wind up with that Monday-morning ache.