The short answer. The habits with the clearest evidence against them are carrying extra weight, letting the muscles that straighten the knee get weak, and brushing off knee injuries, because each is linked with a higher risk of knee osteoarthritis1,2,3. Avoiding exercise does not appear to protect the knees either: in one large review, recreational runners had less hip and knee arthritis than people who did not run4. Most of these habits can be changed.
The ends of the three bones that meet at the knee are covered with articular cartilage, a smooth, slippery layer that cushions the bones as you bend and straighten your leg5. Cartilage does not heal itself well once it is damaged6, which is why the habits that load or injure the knee over the years matter.
The five covered here, each with the research behind it:
Yes, and the effect is larger than the number on the scale suggests. In a study of 142 overweight and obese older adults with knee osteoarthritis, each pound of weight lost was linked with a fourfold reduction in the load on the knee with every step7. MedlinePlus gives a similar estimate for stairs: every pound you are overweight puts about 5 extra pounds of pressure on the kneecap going up and down8.
Extra weight also raises the chance of developing arthritis. A review of 14 prospective studies found that, compared with people of normal weight, overweight people had about 2.5 times the risk of knee osteoarthritis and obese people about 4.5 times the risk1. The reverse also appears to hold. In the Framingham Study, women who lost about 11 pounds (a drop of 2 body mass index units) over 10 years had less than half the odds of developing symptomatic knee osteoarthritis9.
If you already have knee arthritis and are overweight, the American College of Rheumatology strongly recommends weight loss. Losing 5% of body weight can make a difference, and the benefits keep growing with larger losses10.
They appear to. A 2022 review of 11 studies and 46,819 people found that weakness in the muscles that straighten the knee was linked with 85% higher odds of developing painful knee osteoarthritis in women and 43% higher odds in men2. The authors concluded that building that strength may help prevent knee osteoarthritis2.
For people who already have arthritis, the American Academy of Orthopaedic Surgeons (AAOS) notes that specific exercises can increase range of motion and flexibility and strengthen the leg muscles5. A 2024 Cochrane review of 139 trials with 12,468 participants found that exercise probably improves pain, function and quality of life in the short term11.
No. A review of 25 studies covering more than 125,000 people compared runners with people who did not run4:
| Group | Hip or knee arthritis |
|---|---|
| Recreational runners | 3.5% |
| People who did not run | 10.2% |
| Competitive (elite or international) runners | 13.3% |
The authors concluded that both a more sedentary lifestyle and years of high-volume or high-intensity running were associated with hip and knee arthritis. They could not tell whether running caused these differences or whether something else, such as earlier injuries, explained them4.
Both major guidelines back exercise for knee arthritis. The American College of Rheumatology strongly recommends it10, and the AAOS guideline strongly recommends supervised, unsupervised or water-based exercise over no exercise12. A 2025 analysis of 217 trials found aerobic exercise was likely the most beneficial type for pain, function, walking and quality of life, with moderate certainty13.
What matters is the dose. The AAOS suggests switching from high-impact activities such as jogging or tennis to lower-impact ones such as swimming or cycling, which lets you stay active with less stress on the knee5. MedlinePlus adds a few practical habits: warm up before exercise and cool down after, walk down hills rather than running down them, and cut back on or change your exercise to relieve or prevent knee pain8.
They change how force travels through the knee. In a small study of 20 healthy women, walking in their own high heels increased the force across the kneecap joint and the compressive force on the inner side of the knee by an average of 23% compared with walking barefoot14. The authors suggested this may predispose the knee to degenerative changes; the study measured forces, not who went on to develop arthritis14. The same team later found that men's dress shoes and sneakers did not significantly change the knee forces they measured15.
Yes. A 2025 review of 131 studies found that a previous knee injury was linked with higher odds of developing knee osteoarthritis seen on X-ray (odds ratio 2.67)3. Together, overweight or obesity and previous knee injury accounted for 14% of new cases of knee osteoarthritis seen on X-ray3. The link is especially strong for the anterior cruciate ligament (ACL): pooled data from 13 reviews showed close to a sevenfold increase in the odds of knee osteoarthritis after an ACL injury16.
Two practical points follow. First, MedlinePlus advises contacting your health care provider if knee pain follows an accident or injury8. Second, some injuries can be prevented. Pooled data from eight meta-analyses showed that ACL injury prevention training programs cut the risk of ACL injury by half across athletes, and cut non-contact ACL injuries by two thirds in female athletes. There was not enough data to judge the programs in male athletes17.
For knee arthritis, the evidence is encouraging. The American College of Rheumatology notes that exercise programs tend to work better when they are supervised, often by physical therapists, than when people do them alone at home10. In a trial of 156 people with knee osteoarthritis, those assigned to physical therapy had less pain and disability at one year than those who received a cortisone injection18.
At this practice, physical therapy comes before orthobiologic treatments such as PRP in the order of care.
MedlinePlus advises contacting a provider if8:
If you are in the Santa Barbara area, Dr. Scheinberg can examine the knee, review any imaging and talk through the options. See knee conditions or call (805) 682-1394.
Short answers to the questions patients ask most.
Have a question about your own situation?
Call (805) 682-1394Not well on its own. Cartilage does not heal itself well, which is why surgeons have developed techniques to stimulate the growth of new cartilage6.
They can when arthritis is affecting walking, stability or pain enough to call for an assistive device. For those patients, the American College of Rheumatology strongly recommends a cane, and strongly recommends a knee brace for people who can tolerate the inconvenience of wearing one10.
Reviewed by Dr. Richard Scheinberg, MD, a board-certified orthopedic surgeon in Santa Barbara with 40 years of surgical experience.
