It has been a common belief for years that squatting is bad for your knees and that lifting weights will wear out your joints. I don’t know where this idea came from, but whoever decided this obviously did not squat with a loaded barbell and train it over a long period of time. When I was in PT school and early in my clinical career, squats were still pretty taboo in the medical and rehab setting. This does appear to have changed in the last 10 years with squatting being more accepted and people seem to be more on board with the usefulness of them, however it is not prevalent enough and still not loaded enough to really reap the rehab and strength benefits.
Knee pain is often attributed to arthritic degeneration or structural issues such as meniscus tears. Squatting is often cautioned against by medical and healthcare professionals in the presence of knee pain and they often claim it will lead to arthritis and joint damage. This article will provide some evidence to show and explain how lifting weights including squatting can actually help improve knee pain and does not cause arthritis or meniscus tears. At the end of the article, I also share a situation where I experienced a significant knee issue and used lifting to resolve it.
Squatting is a fundamental part of life. You squat in some form or fashion with any movement involving sitting down and standing up (10,11). It seems crazy to think that people often say “I can’t squat, yet they sit down and stand up from chairs and toilets all day long… Or that there are still people out there saying “squats are bad for your knees” while sitting down and standing up all day everyday and are still able to walk afterwards!
Knee pain and pain in general is a part of life. It will happen whether you lift weights or not. Pain is a highly complex experience and cannot be reduced down to only mechanical factors. When talking about the presence of arthritis, the degree to which the pain, if present at all, can affect the individual can also be influenced by other factors outside of the knee itself and the degree visible on imaging does not always have a direct correlation to the severity of pain (5).
“In fact, both well and poorly functioning knees can have similar damage, making it difficult to correlate relevant MRI findings with the patients’ knee pain” (6)
However, lifting weights can certainly decrease the prevalence and severity of it and allow you to better tolerate daily activity demands and handle more physical stress. Squatting can and is an effective rehabilitation tool for improving knee pain and lower extremity strength (11). Despite common belief, lifting weights and squatting can and will make your knees better.
Another area where lifting weights has actually shown benefit when common knowledge would have you think it would be the opposite is with joint hypermobility. You would think if a joint was hypermobile and unstable that applying more load would potentially worsen the issue. In terms of knee pain related to joint hypermobility, there is some evidence that lifting weights can actually help:
“There is even evidence that progressive resistance training improved knee pain symptoms in young women with knee joint hypermobility.” (7)
As with any lift, the complexity of the squat movement pattern allows it to be modified and adjusted in many, perhaps infinite ways to accommodate a pain issue or injury as well as gradually load and address the affected area (10). Some modifications and the reasons for doing so include (adapted from Straub et al):
More forward trunk lean which will decrease amount of knee bend and potentially reduce load on the knee and quads such as with patellofemoral pain issues or anterior knee pain after ACL surgery
More upright trunk which will increase bend of the knee and potentially put more work on the knee and quads to improve knee tolerance to loading and perhaps bias quad strength more
Varying stance widths and degrees of toe-out to find a more comfortable “groove” for knees to move in as wider stances may encourage more hip dominant squatting and allow for reduced stress on the knees, more narrow stance to help more anterior movement and loading of the knees
Starting with a wider stance and forward trunk lean for hip biased squatting in the acute to sub-acute phase of knee pain or injury and gradually transitioning to more narrow stance and knees forward squatting to improve knee tolerance and capacity.
Varying squat depth anywhere from some degree of partial ROM to completely full ROM to accommodate around painful depths then gradually increasing.
Knee pain associated with arthritis:
First of all, arthritis is not simply a wear and tear condition:
“The determinants of pain in osteoarthritis are not well understood, but are believed to involve multiple interactive pathways that are best framed in a biopsychosocial framework (posits that biological, psychological and social factors all play a significant role in pain in osteoarthritis).” (8)
Even the degree of arthritis changes noted on imaging does not directly correlate with symptoms:
“many individuals with grade 3 or higher have no pain, and pain does not often correlate with the severity of knee osteoarthritis. Recently, joint inflammation measured by magnetic resonance imaging (MRI), such as synovitis and bone marrow lesions (BMLs), has also been considered a trigger for pain; however, the relationship between self-reported pain and MRI findings is only weakly correlated.” (4)
A very important aspect where lifting and squatting can help with arthritis is by improving strength. Getting stronger has been shown to improve symptoms with knee osteoarthritis, and a common finding noted in symptomatic knee arthritis is strength deficits, particularly in the quads (1, 2, 5, 8, 11). Strength training has even been shown to substantially reduce pain and improve physical function as well as quality of life in people with knee osteoarthritis (3). Exercise can have a pain reducing effect and weightbearing exercise (such as squatting) can have an even greater analgesic effect on knee osteoarthritis (4).
Anterior knee pain/Patellofemoral pain and squatting:
A common place for knee pain to occur is around the knee cap which is often termed patellofemoral pain. An example way to squat, from Straub et al, to help improve this situation is to begin with more hip biased squatting in the acute phase of the pain episode and gradually transition to more quad biased squatting. Beginning with something like a wide stance low bar squat involving more forward trunk lean and transitioning to more narrow stance with less forward trunk lean, then potentially working towards a heels elevated high bar squat can gradually place more and more load and demand on the knees over time, improving their tolerance and capacity once the acute pain has subsided.
ACL and squatting:
I tore my ACL and had it repaired in my last year of college football. Afterwards I did not know if I could ever squat again, let alone with weight. I did not know if this would stress the new ACL or cause damage. This was in 2009 and there was little information out there about this at that time. I eventually decided I wanted to squat more than I was worried about anything “bad” I could be doing to my knee and in hindsight, it was the right thing to do and perfectly ok in terms of my repaired ACL. Squatting does not place much stress on the ACL and has been found to place less stress on the ACL than walking (10). From Neitzel et al, the squat decreases shear on the ACL by 3 mechanisms:
The squat involves co-contraction of the hamstrings with quadriceps, which stiffens the knee and decreases anterior shear from the pull of the quadriceps when the hamstrings are activated
The squat is a weightbearing exercise which causes increases in joint compression that reduces tension and shear on the ACL
Gastrocnemius (calf muscle) contraction aids in stabilization of the tibia which indirectly reduces amount of anterior shear forces at the knee
Oftentimes after ACL reconstruction, anterior knee pain can be a limiting issue. One way to squat around this and potentially avoid this occurring is to squat in a way that reduces anterior knee stress. Hip biased squatting may be a more appropriate way to begin squatting initially to reduce donor site pain (such as patellar tendon graft) because it involves a more forward trunk lean with places more of the workload on the hips and also involves a some degree less of knee flexion ROM (11). You do not have to stay only with this style of squatting as it is likely a great entry point to get started and build off of but can be progressed to more knee loading styles of squatting. It is actually a good idea to gradually work in some more narrow stance, upright torso squatting which would increase stress on the anterior knee which would allow for improving knee tolerance and capacity later on in the rehab process (11).
Meniscus tears and other imaging findings:
Another structural issue that knee pain is frequently attributed to is meniscus tears. This is also another instance where the presence of meniscal tears does not mean it/they are the source or cause of pain.
“There was no consistent relation of meniscal tears to the presence of pain.” (5)
Oftentimes when imaging is done on knees, there are going to be structural findings such as tears and degenerative changes. However, whether these are sources of pain is a much more complex issue. Many times there are findings of structural issues on MRI in people who have no symptoms, also, studies to date have found inconsistent associations of structural features to symptoms. Additionally, meniscal tears are nearly universal in persons with knee osteoarthrits and are unlikely to be a cause of increased symptoms (5, 6). This may be a large part of why people who undergo arthroscopic procedures to address abnormalities found on MRI do not result in better outcomes than sham surgery (6).
A lot of structural issues and changes that can be seen on imaging may just be normal age related changes and are nothing to worry about, particularly if non-symptomatic. Even if there are knee pain symptoms in the absence of an acute injury, it is very difficult to reliably discern where it is coming from based on imaging. The better action is to find an appropriate starting place with lifting and get to moving.
Lifting heavy and knee pain:
Lifting heavy can be a great, effective, and appropriate way to help resolve knee pain. There is research evidence that there are better results with knee pain and high-intensity resistance training with regards to improving strength, reducing pain, and improving functional ability (8). The evidence also suggests that heavy lifting does not exacerbate joint problems in middle-aged and older individuals and likely leads to superior results compared to conventional therapeutic rehabilitation exercises. Using an intensity of ~ 80% of 1RM slowed disease progression in knee osteoarthritis patients by favorably impacting cartilage morphology, thereby disproving the notion that high-intensity resistance training is not feasible in knee osteoarthritis rehabilitation. (8)
My personal example of lifting weights and squatting to resolve a knee pain issue:
I had an instance where my left knee locked up and was markedly painful, making it very difficult to walk and nearly impossible to squat. I had noticed the knee was more stiff and sore than usual one day after mowing the yard, but felt pretty good lifting the next morning after squatting. When I was deadlifting towards the end of the session, I noticed a weird nodule on the side of my knee cap that felt like it was getting caught when I tried to straighten my knee and was painful. I had to keep my knee from fully extending with deadlifts, but after that it seemed to feel ok for most of the day. Then at the end of the work day I knelt down on that knee and noticed standing up that it started to get really painful on the lateral side. I sat down on a low stool in a deep squat position after that and my knee locked up and became very painful. I could barely limp out to my truck after that. I had to call into work the next day as I could barely walk. I couldn’t straighten my leg and couldn’t bend it more than 80-90 degrees. I was only slightly better the following day but I could tolerate walking enough to go back to work. I finished out the work week and was doing ok walking, but had to keep my knee bent and had to make sure not to make any quick or twisting movements. I didn’t train any the rest of the week as walking at work was all my knee wanted and I didn’t feel like trying to navigate the basement stairs to get to my basement gym. By that weekend I was frustrated and determined enough to get down to the basement and see what I could do to get training again. I figured out I could do some backward sled drags and having to push through my left leg was making my knee feel better. I also did some bodyweight squats to a bench for a few sets of 5 which were tolerable as long as I didn’t try to fully extend my knee when standing up. I also figured out I had minimal issues with deadlifts but at lighter weights. That Monday I decided to resume my normal training routine but with modifications to squatting and lower weights on deadlifts. I squatted with the bar and did the ROM that my knee would allow which was about a ½ squat for 3 sets of 5. I was able to deadlift I think around 225 for a few sets without issue as well. I trained 3x/week, squatting and deadlifting every session. I slowly added weight but focused more on increasing ROM with squats every session. I also added weight to deadlifts each session as I felt I could. I believe I was back to squatting full ROM and around 185-225lbs about 2 weeks after the pain issue started and deadlift weights were back to normal by then. I believe around 2-3 weeks after the issue started I was able to fully bend and straighten my knee. Within 2-3 months of this happening I was back squatting some of the heaviest weights I had in the previous few years without issue and my knee was for all intents and purposes completely normal.
To summarize how I used lifting and training to resolve my knee issue:
Once the pain was tolerable enough that I felt I could do some sort of training, I started loading my knee and leg. I used my normal training plan but made modifications to accommodate my knee and work it as it would tolerate and allow. I progressed this each session, either weight and/or ROM if my knee allowed, and within a couple weeks I was back to training normally and my knee felt mostly normal. Basically I just continued to train but the focus was temporarily shifted to training for my knee instead of overall strength.
Here’s what I did not do:
Freak out and rush to the doctor to find out what was going on with my knee
I took it day by day and noticed there was something that was a little bit better each day, so I kept on going. I didn’t need to find out what the cause was or have any sort of imaging done. I knew it was going to get better and getting an injection or possibly surgery wasn’t going to be the answer
Completely avoid lifting
Yes I had to lay low for 5-6 days but once I felt I was ready and my knee could tolerate it, I got back to lifting
Put any timeline on what I expected as far as healing
I didn’t know how long it would take to get back to normal, but I shifted my focus to appreciating being able to lift again and curiously observing how my knee behaved and improved during and after each session and what it was able to do by the next lifting session
Do any special rehab program or corrective exercises:
I stuck with my normal training plan with modifications to affected lifts – mainly squats and a bit with deadlifts
The squat was enough to work and stress my knee and help to regain ROM
Also, loading my knee and leg was what ultimately made it better. Only lifting could really provide this stimulus
Special treatments, stretches, or soft tissue work
I trained as I could and walked around doing my normal daily activity as my knee would allow. I would bend and straighten my knee for some reps at times just to move it, but that’s it. I didn’t worry about the fact that I had limited ROM and couldn’t straighten my knee, I just worked the movement that I could. I noticed over time as the pain improved and the strength was coming back, my knee bending and straightening was improving. Eventually my knee could fully straighten without pain. This happened on its own over time. I didn’t force it as I knew the pain was a protective response. I just worked what I could right up to the edge of pain and over time that ROM started to free up to eventually being normal.
I think the most important thing the lifting did for resolving the knee issue was allowing me to regain confidence that my knee could be loaded and I could still use it to squat and train. Once I figured this out the weekend after it started, the pain and my whole perception of the issue changed instantly and began making marked improvement. This is why I believe lifting is the most valuable and effective way to rehab an injury.
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