The Best (And Worst) Exercises for Knees, According to a Top Orthopedic Surgeon

Meet Dr. Adam B. Cohen. He’s the Director of Sports Medicine at OrthoManhattan and a board-certified orthopedic surgeon with decades of experience in arthroscopic, robotic, and knee and shoulder surgery.

Dr. Cohen is here to demystify your bone health—from the worst things you could do to your bones to whether collagen supplements actually help your joints. His insights might (literally) change the way you walk through life.

Ready? Let’s dive in:

1. Can I do squats and lunges if I have “bad knees”?

It depends on what you mean by “bad knees.”  

Knee pain can stem from many causes. Arthritis. Meniscus tears. Ligament damage. It could even be pain originating from your hips or ankles! That’s why getting a clear diagnosis is the first step before deciding which exercises are right for you.

That said, squats and lunges aren’t inherently bad for knees. When done right, they actually strengthen the muscles protecting the knee joint, including the quads, hamstrings, glutes, and calves.

But not all knees tolerate these exercises.

Squats can stress the knee joint, while lunges put a high load on the front of the knee—especially if your knee travels too far forward or your hips aren’t quite in control.

For those with patellofemoral arthritis, I suggest modifying your lunge depth, limiting how far your knee travels forward, or using support. And in more painful cases? It might be best to skip these exercises altogether.  

Quick Tips:

• Modify when needed – Try partial squats or swap in lower-load alternatives like step-ups or wall sits.
• Strengthen around the joint – Emphasize hip and core strengthening to offload stress on the knees.
• Listen to your body – Discomfort in the muscles is normal; sharp or lingering joint pain is a sign to back off or adjust.

2. What are the best and worst exercises for knees for women over 50?

It’s not about your age—it’s about your knee’s condition. I’ve helped 70-year-olds train for marathons and seen 30-somethings needing joint replacements. Age is just one part of the picture: It’s joint health that matters most.

Before we dive into exercises, it helps to understand how your joint cartilage functions. This smooth, cushioning surface at the end of your bones is maintained by cells called chondrocytes.

These cells thrive under moderate physical stress, which helps maintain cartilage health. But too much stress can harm them—and damaged chondrocytes are vulnerable to further breakdown.  

That’s why the right kind—and right amount—of movement is so important.

Best Exercises

Low-impact exercises that strengthen the muscles supporting the knee are generally the safest and most effective. Some of my go-to options include:

• Swimming or water aerobics
• Step-ups (using a low step)  
• Stationary biking  
• Pilates  
• Tai Chi  
• Yoga

Exercises to Be Cautious With

Certain movements can increase stress on the knees and are best avoided if you’re dealing with pain, arthritis, or prior injuries. They include:

• Deep squats or lunges with heavy weights  
• Heavy leg extensions on gym machines  
• Running or jumping on hard surfaces  
• Deep-flexion yoga poses  

3) What are your thoughts on glucosamine for joint pain?

Glucosamine occurs naturally in healthy cartilage and is popular for managing osteoarthritis symptoms, a degenerative joint condition where joint cushioning gradually disintegrates.

According to the American Academy of Orthopaedic Surgeons (AAOS), glucosamine may be helpful in reducing pain and improving function in patients with mild to moderate knee osteoarthritis, but the evidence is inconsistent and limited.

For that reason, I don’t routinely recommend it. Not because it’s unsafe, but because we simply don’t have strong enough data.

4) Does collagen help my joints as well as my hair and skin?

Collagen is a major component of cartilage, the connective tissue that cushions your joints. The theory is that if you consume collagen peptides, your body might use them to help repair or strengthen joint cartilage.

It’s a compelling idea. But when it comes to real-world evidence—especially for those with osteoarthritis—the picture is murky.

There’s limited research on collagen peptides for osteoarthritis. Most studies focus only on pain relief, such as one 2023 meta-analysis that found that collagen supplements led to modest pain relief compared to placebo (Journal of Orthopaedic Surgery and Research, Zhang et al).

However, there’s not much research on whether the supplements actually improve cartilage, slow disease progression, or reduce long-term arthritis risk.

That’s an important distinction. To put it in perspective: Tylenol can reduce pain, but that’s different from saying it “helps” your joints.

More rigorous, long-term studies are needed to figure out whether collagen can actually protect cartilage or change the course of osteoarthritis—not just reduce the symptoms.

5) What’s the worst thing people do to their bones?

Common culprits include:

• Drinking too many cola-type sodas. They’re full of phosphoric acid, which likely interferes with calcium absorption.
• Excessive caffeine or alcohol consumption. Both of these decrease calcium absorption and increase calcium loss.
• Smoking. This bad habit disrupts your body’s ability to effectively use calcium and vitamin D.
• Avoiding sunlight or not supplementing vitamin D. Both of these lead to inadequate calcium absorption.
• Under-exercising. This deprives your bones of the necessary stress to build and maintain strength.

Fortunately, each of these habits can be improved through diet, exercise, lifestyle changes, and targeted supplementation.

A huge thank you to Dr. Adam B Cohen for sharing his insights!

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