Knee Strengthening in Real Life: How I Train Clients With Knee Pain
Updated: 5 days ago
If your knees hurt when you exercise, you probably don’t need to stop exercising. You need to change the exercise.
That sounds simple, but it is probably the most important principle I use when working with people who have knee problems.
I’m a personal trainer and strength coach based in Kentish Town, NW5. Over the years I’ve worked with clients dealing with osteoarthritis, significant joint degeneration, ACL ruptures and reconstructions, ligament damage, persistent knee pain and people already having conversations with consultants about surgery or knee replacement.
Often they have been told something fairly straightforward: if they want to give themselves the best chance of maintaining function and delaying surgery, they need to make their legs stronger. That is where I come in.
My job is not to diagnose your knee
The first thing I want to establish when somebody comes to see me is what they already know.
What have they been told by their doctor? Have they seen a physio? Have they had an MRI? Have they seen a consultant or surgeon? What can they currently do? What hurts? What doesn’t? What are they actually trying to get back to doing?
That information is useful because it gives me boundaries.
I am not a physio and I am not a doctor. I am not trying to diagnose what is happening inside somebody’s knee. I am a strength coach.
My job is to work out where that person can start strength training, and then help them get stronger from there.
In that sense, the process is not fundamentally different from helping somebody improve any other exercise. If somebody told me their bench press technique had always been poor, I would watch them press, work out where they can create good tension, look at what range of motion they can control and then build from there.
With a knee problem, the stakes may be higher and the starting point may be very different, but the underlying principle is the same.
Knee strengthening starts with finding your place on the continuum
I tend to think about exercises as sitting along a continuum.
For somebody with a significant knee problem, the beginning of that continuum might be incredibly simple.
Can you lie on the floor and bend and straighten your knee through a comfortable range of motion? If you can do that, can you hold the leg straight? Can you straighten the knee against a small amount of resistance? Can you use a leg extension machine through a range you can control? Can you squat to a high bench? Can you load that squat? Can you eventually move towards deeper squats, split squats, step-ups and more demanding single-leg work?
You keep moving along the continuum until you get to the point where the exercise becomes too challenging, the movement quality deteriorates or the symptoms tell you that you have gone far enough. That gives you your starting point.
It is very rare that somebody genuinely cannot do anything. If somebody cannot tolerate any kind of knee-dominant or quad-dominant exercise at all, then that is the point where I would want them to go back to their physio or medical team. In my career, I could probably count the number of times that has happened on one hand. There is nearly always something we can do.
The simplest-looking knee exercise is not always the easiest
This matters because people sometimes choose exercises that look basic but are actually quite demanding.
A step-up is a good example. It looks simple. You are just stepping onto a box. But it also requires balance, stability, coordination and enough strength to control the whole movement.
If somebody has significant knee pain and poor lower-body strength, the thing limiting the exercise might not even be the muscle we are trying to train. That is not particularly useful.
In that situation, something like a straight-leg raise, a terminal knee extension or a leg extension machine may actually be a much better choice.
They are simpler. You have more control over the range of motion. You can concentrate on the target muscle. You can control the resistance. And, importantly, you can make the exercise gradually harder.
A useful exercise is not just one somebody can do today. It needs to give us somewhere to go next.
Can you actually feel the muscle working?
One of the simplest things I look for is whether somebody can create reliable tension in the muscle we are trying to train.
If we are working the quads, for example, can you actually feel your quadriceps working? If you do 15 or 20 repetitions, can you create that familiar burning sensation in the muscle?
If the answer is yes, that is reassuring. It tells me that we have an exercise where we can create some meaningful muscular tension. From there, we can start making it stronger.
We are trying to increase the strength, and often the size, of the muscles around the knee so that the whole system has more capacity. I sometimes describe those muscles as the suspension or armour around the joint.
The knee does not work in isolation. The muscles around it are what allow it to move and help control the forces going through it.
Should you exercise if your knees hurt?
Usually, yes, but you may need to change the exercise, the range of motion or the load rather than simply pushing through the same movement.
Some people come into the gym already in pain. If somebody has fairly advanced knee problems, they may feel discomfort when they are sitting down, walking around or going up and down the stairs. So simply saying, “Only do exercises that don’t hurt,” is not always particularly useful.
What matters more is how the discomfort behaves. Does the pain get progressively worse as we exercise? Does the knee feel significantly worse afterwards? What does it feel like later that day? What does it feel like tomorrow? What does it feel like the day after that?
That feedback becomes incredibly important.
There also has to be trust between the coach and the client. I can look at an exercise from the outside. I can make sure the technique looks sensible, that the movement is controlled and that we are not doing anything obviously inappropriate. But I cannot feel somebody else’s knee. The client has to tell me what they are experiencing.
Over time, people also get better at understanding those sensations.
Someone with a chronic knee problem can find it difficult to distinguish between normal muscular fatigue, the normal feeling of putting some load through a joint and a genuine aggravation of their symptoms.
That takes communication, patience, and gradually building confidence in what the knee can tolerate.
Why the first strength session may feel underwhelming
I would rather someone leave their first session thinking, “Was that it?” than leave having completely overdone it.
We need information.
If we choose relatively simple exercises, keep the volume sensible and then see how the knee responds over the next 24 or 48 hours, we have learned something useful.
If everything feels fine, we can do a bit more next time. If you go into the first session and absolutely hammer somebody, then they wake up the next morning with a hugely aggravated knee, we have learned very little other than the fact that we did too much.
Progress is much easier when you build from slightly too little than when you repeatedly have to recover from doing too much.
The biggest mistake with knee pain is often doing nothing
The most common reaction to knee pain is understandable. People stop.
Their knee hurts, so they stop training it and hope that rest will make it better.
Sometimes rest is necessary. But if resting the knee also means allowing the muscles around it to get progressively weaker, that creates another problem.
A joint is not just the bones themselves. The muscles around the knee are what make it move and help control it. So rather than thinking purely about resting the knee, I would rather think about finding a way to continue strengthening the muscles around it.
That means the quads, hamstrings, glutes and calves. It usually means finding a way to work each leg independently as well. You also want reasonable control through the trunk and pelvis because hip and pelvic stability can affect what happens further down the chain.
There is no magic muscle here. You need to get the whole system stronger.
This is strength training, not a separate kind of rehab training
I do not really divide what I do into “rehab-style training” and “normal strength training”. It is all strength training. We just start in different places.
The basic principles I use with somebody who is trying to avoid a knee replacement are fundamentally the same as the principles I would use with somebody who wants to squat 200kg.
Choose an appropriate exercise. Make sure the technique is good. Give it a target repetition range. When they can comfortably achieve the top of that range, increase the resistance. Then keep going.
Obviously, the actual exercise might look completely different. One person might be doing a controlled single-leg leg extension with a very light weight. Another might be squatting a heavily loaded barbell. But the training principle is the same.
If somebody needs treatment from a physiotherapist, they should see a physiotherapist. Physiotherapy and strength training can complement each other extremely well. But when somebody comes to me, my job is to help them strength train.
Are squats, split squats and knees-over-toes exercises bad for painful knees?
It depends.
If somebody has very advanced knee problems, then some of the classic exercises that place a lot of demand through the knee are probably not going to be appropriate initially. A deep split squat, a very deep squat or a heavily loaded knees-over-toes position may simply be too much.
But that does not mean those movements are inherently bad.
For somebody with milder knee issues, they can be extremely useful. Something like a front-foot-elevated split squat allows a deep range of knee flexion. A heels-elevated goblet squat can allow somebody to sit very deeply into a squat.
Done with appropriate loading, good control and within the person’s active range of motion, those movements can help somebody develop strength and tolerance through positions they previously found difficult.
The question is not really whether an exercise is good for knees or bad for knees. The question is whether that particular person currently has the capacity to do it.
Client example: from ACL surgery back to tennis and skiing
One client I worked with came to me shortly after having an ACL reconstruction.
She had originally ruptured it playing tennis. After the surgery, she was hobbling into the gym with a brace on her knee and using a crutch.
Her physio had already explained that she needed to improve the strength in her lower body. She happened to be a doctor herself, so when she came to see me the conversation was fairly straightforward. She basically said: I know what I need to do. I need to make my leg stronger. Can you help me do that?
Initially, we focused heavily on her glutes. We used exercises like hip thrusts and Romanian deadlifts because they allowed us to train the lower body without placing huge demands through the knee.
We then included one main knee-dominant exercise in each session. One of the exercises that worked particularly well was a single-leg leg extension.
She could work slowly through a controlled range of motion, feel the quadriceps working and, importantly, we could clearly see the difference between the operated leg and the other side. That gave us something measurable to improve.
Over time, we built the operated leg back up until the extension strength was essentially equal between sides. From there we progressed into split squats, rear-foot-elevated split squats and progressively more normal lower-body training.
Eventually she returned to playing tennis every week. She also went back to skiing. She no longer trains with me, but she is still training and doing brilliantly.
Client example: painful knees back to hiking and climbing
Another client came to me in his late twenties. He loved hill walking, camping and climbing, but described his knees as basically being “trashed”.
They were sore, inflamed and very stiff. He struggled to fully straighten them, and whenever he tried to strengthen his legs it seemed to aggravate the problem.
So we started much further down the continuum.
Initially, there was a lot of very simple work: leg-lowering exercises, wall sits, calf stretching, hamstring stretching and hip flexor stretching.
The aim was partly to improve the available range of motion and partly to help him become comfortable creating tension around the knee again.
There seemed to be an element of inhibition there. Because the knees had hurt for so long, he had become reluctant to use the muscles around them properly. So part of the process was simply showing him that he could.
Once that started improving, we moved onto relatively simple strength exercises. Trap-bar deadlifts worked well because we could load the lower body without asking for huge amounts of knee movement.
Then we gradually increased the range of motion and the amount of load he could tolerate. Eventually, he got back to doing the things he wanted to do: hiking, climbing and spending time outdoors.
There was no magical exercise. It was just a case of finding the right starting point and then being patient.
Can you strengthen knees with osteoarthritis or significant degeneration?
If you can find an exercise that engages the muscle and that you can tolerate, then you have something to build from.
You can train. You can recover. You can eat appropriately. You can progressively stimulate the muscles. And you can get stronger.
I like thinking of those muscles as suspension or armour around the knee. The underlying joint degeneration may still be there, but building more strength and capacity around the knee can make a meaningful practical difference to what somebody is able to do.
For some people, that might mean walking downstairs with less difficulty. For someone else it might mean hiking. For another client, it might mean being able to play tennis or ski again.
And for somebody already talking about surgery, success might mean maintaining a good quality of life for considerably longer before surgery becomes necessary.
I would never promise somebody that strength training will mean they never need an operation. That is not a promise I can make. But improving the strength and capacity of the leg can still make an enormous practical difference.
Confidence matters, but hesitation around knee pain is justified
People with knee pain are often described as being afraid of movement. Sometimes they are. But I also think their hesitation is completely understandable.
The exercises required are quite specific. The appropriate range of motion is not necessarily intuitive. The amount of resistance matters. The setup matters. And quite often the right equipment makes an enormous difference.
If your knee hurts every time you try to squat, it is completely rational to become cautious about squatting.
The answer is not simply to tell somebody that they need to be less afraid. The answer is to give them a version of the movement they can actually do.
Then you repeat it. You make it slightly harder. They realise the knee tolerated it. And confidence gradually returns because they have evidence that they can do more than they thought.
Looking for help strengthening your knees in Kentish Town?
I work one-to-one with clients at my gym on Highgate Road in Kentish Town, NW5. If you have already been assessed by a physio, doctor or consultant, I can work within that information and help establish what you can currently tolerate in the gym, then build your strength progressively from there.
You can read more about my Personal Training in Kentish Town or book a consultation to talk through what you are currently dealing with.
Frequently asked questions about knee pain and strength training
Should I stop exercising if my knees hurt?
No, not automatically. If an exercise hurts your knees, the first step is usually to change the exercise, range of motion, load or setup rather than abandoning exercise altogether. If you cannot tolerate any meaningful knee-dominant work, or your symptoms are worsening in a way that concerns you, that is when I would want medical or physiotherapy input.
Can strength training help painful knees?
It can help many people improve the strength and capacity of the muscles around the knee. The important part is finding an exercise you can control and tolerate, then progressing it rather than simply choosing whatever lower-body exercise looks hardest or most functional.
Can I strength train with knee osteoarthritis?
In my experience, many clients with osteoarthritis can still strength train successfully. The starting point may be much simpler, and the response to each session needs to be monitored carefully, but the underlying training principle is still to find tolerable movements and build strength progressively.
Are squats bad for painful knees?
Not inherently. A deep squat may be completely inappropriate for somebody with a very painful, significantly degenerated knee and useful for somebody with a much milder problem. The relevant question is whether you can control and tolerate that particular range and load right now.
Can a personal trainer help after ACL surgery?
A personal trainer or strength coach can help with the strength-training side once it is appropriate to do so and within the guidance you have been given by your medical or physiotherapy team. My role is not to replace that clinical care; it is to help turn the appropriate starting point into progressive strength training.
Can strengthening my legs help if I may need a knee replacement?
Strength training cannot guarantee that you will avoid surgery. What it can do is improve the strength and capacity of the muscles around the knee, which can meaningfully improve function and quality of life for many people. For some clients, maintaining that capacity may also help them delay the point at which surgery becomes necessary.
Where can I get help strengthening my knees in Kentish Town?
I coach clients one-to-one from 39–51 Highgate Road in Kentish Town, NW5. The first step is a consultation where we look at what you have already been told medically, what you can currently tolerate and what you want to get back to doing.
So should you stop exercising if your knees hurt?
No.
You probably need to change the exercise you are doing.
That might mean reducing the range of motion. It might mean reducing the load. It might mean using a machine instead of a free-weight exercise. It might mean temporarily using something much simpler than the exercise you eventually want to do.
But the overall goal remains the same: find a movement you can control, find a way to create tension in the muscle, make sure you tolerate it, then get stronger.
Knee pain changes where you start. It does not necessarily change where you can eventually get to.
