As we get older, our knees take a lot of wear and tear. One of the most common culprits behind knee pain is Knee osteoarthritis (knee OA) — a form of arthritis that affects the cartilage, bones, and other structures of the knee joint. In this post we’ll walk through what it is, why it happens more with age, who is most affected, and what you can do (with your physical therapist!) to feel better and stay active.
What is Arthritic Knee Pain?
Knee osteoarthritis happens when the protective cartilage in the knee gradually wears down. This leads to changes such as:
Bones rubbing or bumping each other,
The joint lining becoming inflamed,
Possible bony outgrowths (osteophytes), and
Stiffness, swelling and pain in and around the knee.
This doesn’t happen overnight — it’s a slow process, often over many years. It becomes more likely as we age, especially if we’ve had prior knee injury, are carrying extra weight, or have certain structural knee alignment issues.
Why Age Matters
Age is one of the biggest risk factors for knee OA. Here are some key statistics:
Globally, the prevalence of knee OA in people aged 15 and over is about 16.0%, and for those aged 40 and over it rises to about 22.9%. PMC
According to the World Health Organization, about 73% of people with osteoarthritis are older than 55 years, and around 60% are female. World Health Organization
In the U.S., about 9.3% of the population is diagnosed with symptomatic knee OA by age 60. PMC
Among adults aged 45-64 in the U.S., symptomatic knee OA affects roughly 7.8% of people; for those over age 65 it rises to about 15.6%. PMC
The annual incidence (new cases) of knee OA is highest in the 55-64 age group. Osteoarthritis Action Alliance+1
In simple terms: as you cross into your 50s and beyond, the risk of developing knee osteoarthritis goes up significantly. The wear-and-tear over years, combined with factors like previous injuries, activity level, body weight, and genetics, all add up.
Who is Most Affected?
While knee OA can occur in younger adults — especially if they’ve had knee injuries or are obese — the “aging” population is more commonly impacted. Some patterns to note:
Women are at higher risk than men in many studies. PMC+1
People who are overweight or obese have a higher risk (because extra weight increases the load on knee joints). BioMed Central+1
The average/median age of diagnosis of symptomatic knee OA in one U.S. study was about 55 years. PMC
Although older age groups have higher percentage prevalence, because there are many people in the 45-64 age range, the number of people with knee OA in that age band is nearly as high as older groups. PMC
For a physical therapy practice, this means many patients in their 50s, 60s and older will likely start showing knee pain from arthritic changes — but they don’t have to just accept it.
What Does Knee Arthritis Feel Like?
In the clinic you may see patients describing:
Gradual onset knee pain (often worse after activity or long periods of standing)
Stiffness in the morning or after sitting for a while
Difficulty going up or down stairs
A “giving way” or instability feeling (due to weakened muscles or altered joint mechanics)
Possible swelling, warmth, or a “grating” feeling inside the knee
Because the condition progresses slowly, patients may attribute the symptoms to “just getting older.” It’s important to recognize that — yes, age is a factor — but there are things we can do to slow progression and improve function.
How Physical Therapy Can Help
1. Strengthening & Muscle Support
Stronger muscles around the knee (quadriceps, hamstrings, glutes) take pressure off the joint and help improve alignment and movement patterns.
2. Improving Mobility & Joint Mechanics
Gentle motion, stretching, and activity modification help maintain joint mobility so the knee doesn’t lock up or worsen stiffness.
3. Activity Guidance
We’ll help patients stay active (which actually helps cartilage health) while avoiding movements that overload the knee. Low-impact aerobic work, proper footwear, and safe stair/step mechanics all matter.
4. Weight & Load Considerations
A study found that for every 5lbs of fat, the load on the knee joint increases by 4lbs. So by losing even just 10lbs, it takes roughly 40lbs of pressure off of the knee joint.
5. Education & Pain Management
Teaching patients about proper biomechanics, pain-relieving strategies, and strategies to avoid worsening the joint helps them stay in control.
Age Groups & What to Know:
Here’s a breakdown of age bands and what to watch for:
40-49 years: Some early arthritic changes may begin. Prior knee injuries, high impact sports, obesity matter. Early intervention is beneficial.
50-64 years: This is often the “sweet spot” for diagnosis of symptomatic knee OA. Pain may become more noticeable, especially with stairs, walking, prolonged standing.
65 years and older: Higher prevalence of knee OA; however, because of other comorbidities (balance issues, bone health, other joints), tailored rehabilitation is critical to maintain independence and mobility.
Key Take-Home Messages
Arthritic knee pain is very common in older adults — age 55 and up is where we start to see the bulk of diagnoses.
You’re not just “old and sore” — knee osteoarthritis is a real joint condition that responds to intervention.
Physical therapy is not too late at any age — strengthening, mobility work, load management and activity guidance can improve quality of life.
The earlier you engage (even if symptoms are mild), the better chance you have of slowing progression and maintaining an active lifestyle.
Age matters as a risk factor, but individual risk also depends on weight, injury history, activity level, and muscle strength/conditioning.
And to the active adults who still want to train like they did when they were younger— the key is finding the right volume that works for you. I personally used to play soccer everyday. But as I have gotten older, and my own personal knee arthritis has started to set in, I found that two days a week of soccer was doable without flaring up my knees. I also strength train and stretch at least 2 days per week to ensure my joints are protected when I step on the field. Sometimes figuring out the “right”" amount of volume takes some trial and error, but it is definitely possible with smart choices and discipline.
Maybe it’s as simple as running 3 miles instead of 4 because you notice at 3.5-4 miles your knees ache for days. And instead of running daily you can choose to run every other day and supplement biking for extra cardio. These are all decisions we can help you with so feel free to reach out with any questions!
