Whether they’re crunching and crackling, or buckling when they should bend, knees seem to reach their expiration date faster than does skim milk. If your knees feel older than you are, the culprit may likely be found between the hours of 9 a.m. and 5 p.m., according to Erik Moen, a physical therapist and founder of Corpore Sano Physical Therapy in Kenmore, Wash. “Many people are at a computer for work, and all that time sitting makes you lose strength in the hip gluteus medius,” says Moen. He explains that this crucial muscle stabilizes your leg from your hip to your knee, and if you don’t keep them strong, your knees will weaken over time.

Another major knee problem can actually come from being too active — if it’s the wrong activity. Your knees are coated with cartilage, which provides a cushion when you move. “But there’s only so much [cartilage] available for a lifetime,” says Moen. “Once it’s gone, it’s gone. Activities such as running for long distances every day or jumping too much can eventually wear it thin.”

While you can’t quit your job or restore the cartilage already lost, there are steps you can take to minimize further damage and maximize knee health as you grow older:

1. Get off Your Feet
Running is a knee killer, and even walking can do slight damage. But that doesn’t necessarily mean it’s time to retire your sneakers. Instead, diversify. “Biking or doing another exercise with less impact every other workout will allow your knees to repair the damage,” says Moen. Remember, you don’t want to stop doing cardio, because excess weight gain can put stress on the knees as well.

2. Positive Posture
When posture is out of alignment, it causes your body to shift weight to the knees at an unhealthy angle. You want your hips to sit over your knees, but that can only happen by training the rest of your body not to hunch. A top exercise to improve posture is the wall sit: Begin by putting yourself in a seated position against the wall; then flatten your lower back, then mid-back, then your head against the wall. Pull your arms back to complete the movement. Hold for as long as you can while maintaining good form.

3. Get a Lift
Sideline leg lifts will improve the aforementioned gluteus medius. Lie on your side with your knees slightly bent, then elevate your top leg 12 to 15 inches past horizontal. Three sets of 12 reps is optimal. Remember to work out both legs.

4. Don’t Ignore Pain
“Listen to your
knees,” says Moen. “Serious knee problems don’t usually start overnight — they
fester.” So if you’re experiencing knee pain, especially if it’s intolerable,
then you need to figure out why you’re having it. Better a doctor’s appointment
now than a knee replacement later!

Eric Butterman Eric Butterman has written health
articles for more than 20 publications, including Glamour, Men’s
Fitness and Shape.