Squat forces on knee cartilage

[Keith Burnett]

Are you aware of excessive or significant shearing forces on cartilage during squats?

No information in your book regarding.

Concerns about squats with chondromalacia. Femur and proximal tibia.

Discussing with my orthopedic buddy.

[Mark Rippetoe]

Pages 16-19 discuss the topic. What are his specific concerns, and has he personally performed a correct squat?

[bjvinson]

I’ll chime in here. I’ve had 2 surgeries to repair torn meniscus in my left knee. The first 38 Year’s ago, the 2nd 35 years ago. So I don’t have much cartilage left in there and squatting isn’t a problem.

[Keith Burnett]

Pages 16-19 discuss the topic. What are his specific concerns, and has he personally performed a correct squat?

I've read the book and pages noted several times. It does discuss the balance of forces in a proper squat, mainly between the posterior chain and the quads as well as the knee ligaments. I will provide the surgeon with some copies of relevant pages.

However , there are compressive forces acting through the cartilage surfaces, primarily the femur and tibia from start to end...
In addition gravitational compression forces act on changing regional cartilage as the surfaces rotate (cycle) against each other. Rotation under compression results in a shearing force. But all the variable involved in a physiological stress are difficult to tease out.

The orthopedist, who probably has not performed a squat, proper or not , in a long while. Since he did not provide citations of biomechanical studies, I don't whether he is riffing on his intuitions or has an evidence based opinion.

So now to his concerns regarding a patient with chondromalacia, synovitis , and effusion. We do not have to get into the ICRS IKCD cartilage scoring or anything like that. We just have to know that a patient, without ligament damage, no meniscus tear, has symptomatic chondromalacia in multiple compartments. His advice to a patient adamant about continuing the lifting, was to significantly decrease the load in lifts, not participate in incremental weight programming, ....ie basically many reps of low weight training....citing his primary concerns as heavy loads, shearing force increased, advancing disease.

Biomechanical studies of stressed cartilage in weightlifting are not easy to find I have some studies that could be relevant...but not sufficient to provide recommendations in a clinical environment, with all the confounders.

[samking7185]

Pages 16-19 discuss the topic

These are very informative illustrations and explanations.

has he personally performed a correct squat?

Notice he said correct squat.

[Mark Rippetoe]

However , there are compressive forces acting through the cartilage surfaces, primarily the femur and tibia from start to end...
In addition gravitational compression forces act on changing regional cartilage as the surfaces rotate (cycle) against each other. Rotation under compression results in a shearing force. But all the variable involved in a physiological stress are difficult to tease out.

And these stresses are compensated for by the cartilage remodeling mechanisms operating at the subchondral level. It is instructive to note that osteoarthritis primarily affects the portion of a joint that is not loaded in compression.

[Keith Burnett]

These are very informative illustrations and explanations.



Notice he said correct squat.

Yes...of course. I noticed the exact wording of his response.

[Bill Hannon]

The synovial fluid in the joint also greatly reduces the coefficient of friction between the articulating surfaces, minimizing the shear forces on the cartilage. It's much like a thin-film lubricated, high-load, low-speed bearing.

[Keith Burnett]

And these stresses are compensated for by the cartilage remodeling mechanisms operating at the subchondral level. It is instructive to note that osteoarthritis primarily affects the portion of a joint that is not loaded in compression.

regarding compensatory /remodeling mechanisms.......you are generally correct as long as the cartilage is reasonably healthy. Once the ultrastructure and molecular capabilities are damaged, then cartilage becomes more and more "'defenseless". The ability to respond to stresses also has a relationship to the orientation of the subsurface cartilage collagen orientation and the direction of the stress....as well as several other factors.

We are getting far into the weeds here when it comes to understanding how already damaged cartilage responds to compressive and shear forces (rotation with compression). Knee biomechanics , although pretty well worked out are complicated. Our understanding of OA , despite lots of biomarkers and ability to map cartilage structure with MR under stress, still far from certain.

Your statement about compression and OA, I just cannot accept on face value. If you have citations and more than anecdotal evidence I am all ears.

However, we are still stuck with compressive forces during the squat (correct according to SS or not) and shear forces at the chondral/subchondral bone junction with rotation. You have deep fissures, clefts, and incipient delamination tears and you scrape them along various surface irregularities under stress. Something happens. Lets fund a study using MRI and T2mapping to see how squatting affects the biology of cartilage. That would be fun.

[Keith Burnett]

And these stresses are compensated for by the cartilage remodeling mechanisms operating at the subchondral level. It is instructive to note that osteoarthritis primarily affects the portion of a joint that is not loaded in compression.

I wrote a lengthy response to yours with lots of interesting scientific developments in OA and biomarkers ,as well as measurements under stress. However, it timed me out and re login did not preserve. therefore....screw it.