A summary of the research on knee pain and exercise

Why is the research important?

There are a huge amount of studies on knee pain and exercise, many of them very strong. They help us to understand what works and what doesn't. Some exercises have been found to be "the best" or the most effective in helping pain and movement.

Before we start, we need to clarify that there are different types of knee pain or knee conditions and the advice for the best exercises is different too.

As always, information from your local physiotherapist or GP is the best place to start and this is general information only.

Types of knee pain

Some knee pain is "acute". This occurs when you from a movement such as twisting in an awkward manner or from a fall that damages the joint causing injury and swelling. The best treatment for your knee at this point is to see your local physio or health professional for a diagnosis. You need to find out exactly what you're dealing with before you start any exercise. Based on the timeframes for damaged tissue to heal, there also needs to be a period of what is called "relative rest" or "protection" and in more extreme cases, total rest or bracing and reduced weight bearing with crutches may be needed (or in some situations surgery is required to mend the ligaments or trim or tidy up a meniscal tear). Often ice, compression and elevation is recommended. Check out this blog post from the British Journal of Sports Medicine on PEACE & LOVE  (the E in LOVE stands for Exercise - more on this below).
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Most knee pain is "chronic" or "persistent". This means it's been sore for a good couple of months or longer. If you're over 45 years old and have pain on activity or movement (and less than 30 minutes of morning stiffness) then you're likely to have knee osteoarthritis. The risk factors to developing knee arthritis are surprising to some as it's not really about just getting older, it can depend what your knee has been up to in the past.
Some of the risk factors can include
- previous injury (such as a meniscal tear or ligament injury like an ACL rupture when you were younger)
- being overweight or obese
- an occupation that involved a lot of load on the knee like being a tradie
Also a family history of osteoarthritis is a risk factor.
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Types of exercise and exercise guidelines

For acute injuries, PEACE & LOVE recommends exercises help to restore flexibility and strength. Pain should be avoided during exercise in these early stages to help repair of damaged issues. The types of exercise that may be most useful in these early stages following an acute injury are gentle flexibility and gentle muscle activation in the position and range of movement that the injury and tissue healing needs.
Often this is a
- small stretching movement (not at the end of the range or the extreme positions for the knee joint) and
- isometric muscle contractions (squeezing or activating the muscle without any movement of the joint).
The exercise in the early stages of acute injury should be guided by your physiotherapist or health professional.

For people with knee osteoarthritis, research shows that the health benefits of physical activity and exercise are overwhelming. All around the world, committees of the smartest boffins in science, medicine and exercise put together “Clinical guidelines” for whole countries and international organisations (NICE, UK; American College of Rheumatology, OARSI) or for whole groups of health professionals (Royal Australian College of GPs).

Exercise is recommended for everyone to improve knee osteoarthritis regardless of its severity, how much pain you have or how hard it is for you to move around.

Let's look more closely at what type of exercise is recommended as the most useful. Specifically for knee osteoarthritis, the most beneficial types of exercise in most guidelines are
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1. Cardiovascular fitness exercise
(getting a bit of huff and puff)

and
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2. Leg strengthening
(making the muscles better able to push our body weight out of a chair, up the stairs or support the joint and take some of the pressure).

In particular it's useful to strengthen
- our quadriceps (front thigh muscle) as it supports and steadies the knee joint.
- the gluteals and the calf muscles are also other important leg muscles to strengthen.

Quadriceps strengthening can include exercises such as
- squats
- step ups and
- lunges as well as
- knee straightening against resistance or weights (such as a leg press).
Gluteal muscles are also often involved in these exercises.
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Bridging is another useful glueteal strengthening exercise.
Heel raises are often used for strengthening the calf muscles.
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Balance exercises are also useful for some people. If you’re stiff, some stretching may be good.

But the main priority is to get fitter and stronger to get the best improvements in your knee pain.

This brings us to physical activity or walking for knee arthritis. The research shows that doing 6000 or more steps per day is likely to mean you are generally doing better. Just like for the fitness and strengthening exercises, start out slowly and gradually increase a walking program.


The key to exercise is to start gradually and build up slowly based on how your pain system tolerates the new exercises. This is called "graded exposure to load". Pain during and after exercise with arthritis is normal. It doesn't mean you are causing any damage. It's your pain system being a bit sensitive or cranky with a new activity. Keeping any changes or increases in exercise slow and steady means your pain system can adapt to the new loads and in time will become less sensitive and your pain will go down. Track your response to exercise in a diary and aim for pain to be at a "reasonable" level from your perspective and ideally not more than a couple of hours after exercise. If you're sore for more than 24 hours, you still haven't done any damage, just recalibrate and do slightly less next time.

One critical point is that walking definitely won’t make your leg muscles stronger. For muscles to get stronger they need to push against enough resistance that after doing it six or eight times, the muscle is exhausted and wobbly and can’t do a single further repetition of the exercise. This concept is part of a resistance training principle called "progressive overload". Until you push the muscle hard enough that it is exhausted, it won’t be stimulated to grow.

Where does aquatic exercise fit in for people with knee pain? Sometimes aquatic exercise is a more gentle way to start with exercise to build confidence and see some early improvements in muscle performance. When you have water up to your waist, your legs and joints are taking 50% less of your body weight. When you have water up to the level of your chest, it’s 70% less body weight. Exercises in water can be less painful than exercises on land for people with knee arthritis. Less pain with exercise can sometimes be helpful when you start out or when you've had difficulties with exercise programs in the past.

We can use water as a kickstart to graduating to coping with bigger loads with walking upstairs or in home or gym-based exercise as our knees get a bit stronger and more used to the resistance and our pain system adapts. Aquatic exercise has been shown to be just as effective in improving pain and walking for people with hip or knee osteoarthritis or other musculoskeletal conditions.

Best of luck with your knee pain and exercise. A reminder that this advice is for general information only. Please check in with your local physio or health professional for advice specific to your condition.

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