Why Your Knees Need a Good PT

By Vincent Hanneken, PT/Owner

We treat many postsurgical patients, and one of the most common procedures we help people with is a TKA (total knee arthroplasty), where someone essentially receives a new knee. Everyone is different, but on average it’s a 4–8-week process to return to a functional level where they can self-manage. The initial goal for someone with this procedure is restoring their range of motion, as this is the foundation for rebuilding strength and function to return to usual activities.

It may be surprising to learn that in the U.S., about 1.3 million TKAs were done in 2023, at a cost of about $39 billion. Of all TKAs done worldwide, the U.S. accounts for 40%, despite being only 4% of the global population. Interesting, isn’t it, how much more per capita this procedure is done here than elsewhere? For example, compared to Germany—a similarly developed country—we did 2.4 times more knee replacements per capita in 2023.

What Can We Do to Slow This Trend?

One might ask: what can we do to slow down the rate of needing this surgery once we reach our 50s and 60s? Projections show that by 2040, TKAs in the U.S. could exceed 3 million annually—a 230% increase over current levels, which are already 2.4 times higher per capita than Germany. This raises valid questions: Will Medicare and insurance be able to support the cost increase? Will there be enough surgeons? How long will the wait be as demand rises?

Considering the rising costs of managing chronic diseases and the current $2 trillion U.S. annual deficit (to put it in perspective, one trillion is a million millions!), we must ask how long this can be sustained. As a result, this article is really aimed at those in their 40s, who may be TKA candidates in the next 15 years. Of course, technology may change the outlook. New procedures could reduce the need for or the cost of TKAs, but the old saying still applies: “An ounce of prevention is worth a pound of cure.”

Reducing Your Risk

It takes initiative to think preventatively, but it’s worth asking: what can you do now to reduce stress on your knees? Ideally, your joints should age more slowly than your chronological age. If you’re 60 and your knees function like a 45-year-old’s, that’s excellent. Sadly, we often hear the reverse, especially about our loadbearing joints: “You have the spine of an 80-year-old, and you’re only 50.” Sobering news.

Keep in mind, a knee replacement is not a pleasant procedure! In terms of pain and limitations, it’s often worse than a total hip replacement in getting back to reasonable function.

Joints are classified into categories. The knee is a hinge joint, meaning it moves mainly in one plane. Our fingers and ankles are other examples. More specifically, the knee is a modified hinge joint, with a small degree of rotation—but generally, rotation is not the knee’s friend.

Two Types of Knee Stress

• Traumatic – due to a specific event, like an accident or a fall
• Degenerative – a breakdown over time from work, sports, and everyday use

We’re focusing on the latter, but that’s not to say people with previous injuries shouldn’t also think preventatively. They should even more so, especially if they’ve already had surgeries, which are common precursors to eventual TKA.

Home Screening Tests

When thinking of prevention, there are two key areas to be attentive to when it comes to the knee’s range of motion: extension (straightening) and flexion (bending). Try these home screening tests to see how your range of motion is looking.

Flexion Test:
Lie on your back on a flat surface. Bending your knee, pull your heel towards your hip. Measure the distance between your heel and your hip. Repeat on the other side and compare. Normal flexion is about 140 degrees, or about 3–5 inches between hip and heel. How do your knees measure up?

Extension Test:
Laying on a flat surface, extend your legs straight. Measure the distance between the underside of each knee and the floor. Ideally, there is no space between the two! Do your knees have full extension?

Full knee extension is vital for walking, as it reduces stress on the joint when your body weight hits the ground. If extension is limited, the result is increased compression and rotational stress on joint surfaces. And as mentioned, rotation and compression are tough on cartilage. You’ve likely heard someone say, “My knee is bone on bone.” That’s from excessive cartilage loss.

Progressive loss of knee extension accelerates cartilage thinning, which—along with pain and limited function—determines when a joint needs to be replaced.

Other Contributing Factors

• Poor core and hip strength, leading to excessive thigh bone rotation into the knee
• Poor foot stability, creating rotation from below
• Excessive load on the quadriceps, increasing patellar stress

The theme here: Repetitive, excessive rotational stress on a joint not built to handle it. This leads to stiffness and degeneration over time, which forces the knee to cope with non-optimum conditions for good cartilage health.

The Good News

There’s a lot you can do to recover knee motion, improve flexibility, and build strength. At any stage, even after injury or accident, there is progress that can be made.

Unfortunately, many people go after the pain and inflammation in their joints with drugs instead of getting to the cause behind it. As long as Advil or Ibuprofen are the first line of defense, it’s going to be very difficult to observe the changes in function and range of motion and to interpret the signals the body is sending.

Painkillers may calm inflammation, but they don’t solve the root issue. Now, the question should be asked: did they contribute to the healing process? Did the cartilage in the joint heal fully, or is it now subtly weaker and wearing out faster?

Cartilage is a key part of joint health, and its longevity is a major factor in joint replacement. If you want to understand cartilage recovery, see our newsletter articles on “Wear Zones” and “Cartilage Health” under Health Tips on our website.

Final Thoughts

If you want to preserve your knees, keep your cartilage healthy, stay active later in life, and avoid a painful surgery followed by weeks of rehab, start paying attention now. Watch for small changes in your motion. Better yet, get evaluated by a movement expert at Full Potential PT. We’ll help you manage the friction and rotational stress that often lead to joint breakdown.

Don’t wait until you hear an orthopedist say, “When you can’t stand the pain anymore, schedule the knee replacement.” That’s a tough way to start retirement.

No matter your age, do the tests and see where you stand, or come in for a free consultation. We can help you identify the key stressors affecting your knees. And if you’re concerned about other joints—shoulder, hip, spine, or ankle—the same principles apply.

Give us a call or talk to your doctor about a referral, and your knees will thank you.