Knee Extension Exercises Hurt My Arthritic Knee — Should I Stop?

If you have knee osteoarthritis (knee OA) and have been told that you need to strengthen your legs, it can be frustrating when the very exercises you have been given seem to make your knee hurt.

https://youtu.be/MiRE2Trqui4

A common example is the knee extension exercise. You try it, your knee becomes painful, and understandably you start wondering:

“If strengthening is supposed to help my knee arthritis, why does this exercise hurt?”

The important point is that pain with one exercise does not necessarily mean that strengthening is wrong for you.

Sometimes we simply need to change the position, range of movement, resistance or exercise itself to find a version that your knee tolerates.

For people with knee osteoarthritis, we don't want to give up on strength and conditioning too quickly. Instead, we want to keep searching for the right way to build strength for your knee.

Why Is Strength Training Important for Knee Osteoarthritis?

Exercise is one of the key non-surgical management strategies recommended for people with knee osteoarthritis.

Strength training can help improve:

• Quadriceps and lower-limb strength

• Walking and physical capacity

• Ability to complete everyday activities

• Pain and stiffness

• Confidence with movement

• Overall physical function

A recent 2026 systematic review and meta-analysis included 120 trials and more than 10,000 participants across the knee osteoarthritis and knee replacement continuum. It found that resistance training improved measures including mobility, walking capacity and knee extension strength in people with knee OA. Importantly, resistance training did not appear to increase risk compared with control interventions.

So, in many cases, the question isn't:

“Should I strengthen my arthritic knee?”

It is:

“How can we find a strengthening program that my knee can tolerate and progressively build from?”

What If Knee Extension Exercises Hurt?

This is where individualising an exercise program becomes important.

Imagine you have been prescribed a seated knee extension exercise and it consistently aggravates your knee.

There are several variables that could potentially be changed before deciding that strengthening isn't suitable.

1. Change the Range of Movement

You don't necessarily need to perform an exercise through its maximum available range.

Certain parts of the movement may be more uncomfortable than others.

We may initially work within a range that you tolerate better and then gradually increase that range as your capacity improves.

2. Change the Position

Sometimes changing the way an exercise is performed can make a significant difference.

For example, strengthening your quadriceps while sitting and straightening your knee is different from strengthening the same muscle group using exercises such as a sit-to-stand, squat or leg press.

One may be uncomfortable while another is well tolerated.

The important thing is that we are still finding an appropriate way to provide a strengthening stimulus.

3. Change the Resistance

The exercise itself might be appropriate, but the resistance may simply be too high for your current capacity.

Reducing the load can allow you to perform the exercise more comfortably.

Over time, the resistance can then be progressively increased.

4. Change the Exercise

Sometimes an exercise simply isn't the right choice for you at that particular point in your rehabilitation.

That's okay.

There are many ways we can strengthen the muscles around your knee.

Rather than repeatedly performing an exercise that significantly aggravates your symptoms, we can look for an alternative that allows you to train effectively.

Does Exercise Have to Be Completely Pain-Free?

This is another important question.

The goal isn't necessarily to ensure that you never feel your knee during exercise.

With knee osteoarthritis, some people may experience a degree of discomfort when exercising.

Instead, we need to consider the amount of discomfort, how your knee responds afterwards and whether symptoms settle appropriately.

There is a big difference between experiencing some manageable discomfort during an exercise and repeatedly performing an exercise that causes a significant or prolonged flare-up.

This is one reason that simply downloading a generic list of “the five best exercises for knee arthritis” doesn't always solve the problem.

An exercise program needs to be monitored and adjusted according to how you respond.

Don't Give Up on Strengthening Because One Exercise Hurts

This is probably the most important message from the video accompanying this article.

If one strengthening exercise hurts, we don't necessarily want to conclude:

“Strength training makes my arthritis worse.”

Instead, we should ask:

“What can we change?”

Can we change the position?

Can we reduce the resistance?

Can we modify the range?

Can we choose another exercise?

Can we reduce the volume and gradually build it back up?

This process of scaling and progressing exercise appropriately is an important part of physiotherapy management for knee osteoarthritis.

What If You're Trying to Avoid or Delay Knee Replacement Surgery?

For some people with knee osteoarthritis, the aim of conservative management is to improve symptoms and physical capacity sufficiently that they can continue doing the things that matter to them without surgery.

Exercise doesn't reverse established osteoarthritis, and we shouldn't promise that strengthening will prevent everyone from eventually requiring a knee replacement.

However, structured exercise remains an important component of non-surgical knee OA management. Clinical guidelines consistently recommend interventions including exercise and education before progressing to surgery.

This is why it is worth searching for a program that works for you rather than abandoning exercise because the first program you tried was painful.

What If You're Already Having a Knee Replacement?

Strength and conditioning can still be valuable.

If you know you are going to have a total knee replacement, the period leading into surgery provides an opportunity to work on your physical capacity.

This is commonly referred to as prehabilitation.

The evidence regarding exactly how much prehabilitation changes long-term surgical outcomes remains mixed. A systematic review and meta-analysis found low-to-very-low certainty evidence that prehabilitation improved knee function before surgery and during the first three months following total knee replacement, but the longer-term effects were inconclusive.

A more recent review also found improvements in several outcomes following total knee replacement but cautioned that high risk of bias and considerable differences between studies limit the conclusions that can be drawn.

The message therefore shouldn't be that getting stronger before surgery guarantees a better surgical outcome.

Instead, we see the pre-operative period as an opportunity to maintain or improve as much strength, mobility and physical capacity as your knee allows.

There Isn't One Perfect Exercise for Knee Osteoarthritis

This is where knee osteoarthritis management needs to become individualised.

Two people can both have knee osteoarthritis and respond completely differently to the same exercise.

One person might tolerate knee extensions very well.

Another might prefer a leg press.

Someone else might initially tolerate sit-to-stands better.

The specific exercise is often less important than finding a way to provide an appropriate training stimulus that you can tolerate, repeat and progressively build over time.

As physiotherapists, we're not simply looking for an exercise that you can do today.

We're trying to establish a starting point from which we can progressively build your capacity.

Keep Searching for the Right Program

If you've tried strengthening exercises for knee osteoarthritis and they hurt, don't automatically assume that exercise isn't for you.

It may mean that that particular exercise, performed in that particular way, isn't right for you at the moment.

Modify it.

Scale it.

Change the position.

Change the range.

Adjust the resistance.

And, when appropriate, progressively build it again.

Whether you're trying to manage knee osteoarthritis conservatively, remain active for as long as possible, or prepare yourself for an upcoming knee replacement, finding a strength and conditioning program that works for your individual knee is important.

At Body Fit Physiotherapy in North Adelaide, we work with people with knee osteoarthritis to assess their current strength, function and symptoms and develop an individualised exercise program.

The aim isn't simply to hand you a list of knee exercises.

It's to help you find the right starting point and the right progression for you.

If you're struggling to exercise because of knee osteoarthritis, we're happy to help.

References

Brown RCC, et al. Efficacy and safety of resistance training for knee osteoarthritis and subsequent knee replacement: A systematic review and meta-analysis. Annals of Physical and Rehabilitation Medicine. 2026.

Gränicher P, et al. Prehabilitation Improves Knee Functioning Before and Within the First Year After Total Knee Arthroplasty: A Systematic Review With Meta-analysis. Journal of Orthopaedic & Sports Physical Therapy. 2022;52(11):709–725.

Adebero T, et al. Effectiveness of prehabilitation on outcomes following total knee and hip arthroplasty for osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Disability and Rehabilitation. 2024;46(24):5771–5790.

Vervullens S, et al. Prehabilitation before total knee arthroplasty: A systematic review on the use and efficacy of stratified care. Annals of Physical and Rehabilitation Medicine. 2023;66(4):101705.