Knees Hurt When Exercising | A Physical Therapist Explains 5 Common Reasons

Do your knees hurt when exercising? You’re not alone. This is a common exercise complaint I’ve seen in my patients. They wonder why this happens and, more importantly, how to avoid it.

And, honestly, the causes vary widely. Some people feel pain because their thigh muscles are weak. Others, because their joints don’t have enough range of motion.

So, this article will walk you through 5 common causes of knee pain while exercising and how to fix each one. Here’s a summary, tap on any of them to go straight to that section:

• 1) Insufficient warm up
• 2) Muscle weakness
• 3) Not enough range of motion
• 4) Unknown injury
• 5) A medical condition
• Tips to avoid knee pain while exercising

Let’s get started:

5 causes of knee joint pain while working out

1) You didn’t warm up properly

Warming up prepares you for the physical activity you’re about to do. Skipping it means your joint won’t be ready for the effort which can increase your risk of having knee joint pain.

Yes, I know spending 10 minutes doing a warm-up can be annoying. It can even feel like a waste of time.

But, studies show it can help you prevent injuries and even enhance your performance by 79%. (1, 2)

That’s a (very) nice advantage worth having, don’t you think?

How to fix this?

Further down you’ll learn how to do an effective warm-up that also protects your knees.

2) Your thigh muscles aren’t strong enough

If you don’t have the strength required for the exercise you’re about to do, your joints will suffer. This will inevitably cause knee pain during exercise and probably afterward, too.

---

---

See, muscles aren’t just for moving. Your leg muscles also absorb the impact from each step so the joint doesn’t have to.

This means having strong muscles can protect your knee joint as well. As a matter of fact, having strong quadriceps and hamstrings is associated with less knee pain and more flexibility. (3)

How to fix this?

Add some exercises to strengthen your knees in your routine to prevent injury.

3) You lack the range of motion needed

Certain exercises need you to have some range of motion available to perform them properly. A common example is a deep squat.

See, to perform this exercise correctly, your knees have to pass your toes and your butt has to end near the floor. You need an ample range of motion in your ankle and hips to do this.

If they don’t have that range available, you won’t be able to do a proper deep squat. This can cause a dull or sharp pain in your knee while doing lunges or squats, among other things.

Also, believe it or not, a lack of range of motion in the ankle is associated with an increased risk of suffering a knee injury. (4)

How to fix this?

Add some ankle mobility drills during your warm-up to improve your ROM.

4) You may have an injury

Patellofemoral pain syndrome, knee osteoarthritis, a sprain, or a meniscus tear can cause knee pain while exercising.

And if the symptoms aren’t severe, the thought of having an injury may not even cross your mind. But this may be the cause of your pain if:

• You had a traumatic event on your knee recently, like falling on your knees
• You play sports that require sudden changes of direction, like soccer or football
• You’ve had a serious injury in your knee before, like an ACL tear
• You also have other symptoms like instability, locking, or swelling

How to fix this?

A knee support may help reduce knee pain while exercising. These knee garments protect and support the knee in different ways, depending on their design and materials.

5) There’s an underlying medical condition

Although rare, some health conditions can cause knee pain while doing physical activity. Common examples include rheumatoid arthritis, arthritic psoriasis, or gout.

These conditions also cause pain while resting, walking, or at night.

How to fix this?

If this is your case, please seek medical attention. A rheumatologist or an orthopedist can identify the root cause of your knee pain.

How to avoid knee pain while working out?

Warm-up before

To be effective, a good warm-up should (2):

• Include movements that you’ll do in your physical activities
• Last 10-15 minutes tops. More than that is overkill
• Increase your heart rate between 50-90% of your maximum heart rate

For example, if your physical activity involves running, your warm-up could include leg extensions, stretching your hip flexors, and jogging.

These 10 minutes of warming up will make sure your knees are prepared for the effort. Thus, avoiding knee pain during your workout.

Focus on resting

Sleeping at least 7 hours each night can be the magic remedy you were waiting for.

See, enough rest and proper stress management can boost healing and decrease pain levels. This in turn will improve your performance and decrease your risk of knee injury. (5)

Follow the progressive overload principle

This means increasing your training intensity gradually. In practice, it looks like running 5-10% more than you did last week, instead of going from 0 to 5k in a week.

---

---

Or do 3-5 more reps of an exercise compared to the previous week, instead of increasing the number of reps, sets, and weights all at once.

Following this principle gives your body the time and space to safely adapt to the new load and avoid injuring yourself.

Go to physical therapy

A physio can help you identify the reason why your knee hurts while exercising.

For example, after a physical evaluation, your therapist may notice that the cause is a weakness of your hip muscles. So, a well-rounded strengthening program will be the solution.

Or, it could be something as simple as not wearing the right shoes for the discipline. This can put more pressure on your knee. In this case, your physio will help you choose shoes that fit your needs.

FAQs:

Conclusion: Knee joints hurt when exercising

Several things can make your knees ache when exercising. If you don’t know where to start, focus on warming up properly and follow the principle of progressive overload.

If the pain doesn’t improve after a few weeks, please visit a physical therapist. This will help you identify the cause, treat it, and exercise safely again.

Resources

1. Fradkin, Andrea J. “Effects of warming-up on physical performance: a systematic review with meta-analysis.” Journal of strength and conditioning research vol. 24,1 (2010): 140-8. DOI: 10.1519/JSC.0b013e3181c643a0
2. Silva, Luís Miguel. “Effects of Warm-Up, Post-Warm-Up, and Re-Warm-Up Strategies on Explosive Efforts in Team Sports: A Systematic Review.” Sports medicine (Auckland, N) vol. 48,10 (2018): 2285-2299. DOI: 10.1007/s40279-018-0958-5
3. Luc-Harkey, Brittney A et al. “Associations among knee muscle strength, structural damage, and pain and mobility in individuals with osteoarthritis and symptomatic meniscal tear.” BMC musculoskeletal disorders vol. 19,1 258. 27 Jul. 2018, DOI: 10.1186/s12891-018-2182-8
4. Taylor, Jeffrey B et al. “Ankle Dorsiflexion Affects Hip and Knee Biomechanics During Landing.” Sports health, 19417381211019683. 6 Jun. 2021, DOI: 10.1177/19417381211019683
5. Finan, Patrick H et al. “The association of sleep and pain: an update and a path forward.” The journal of pain vol. 14,12 (2013): 1539-52. DOI: 10.1016/j.jpain.2013.08.007