Knees Hurt After Squats – Importance of Depth

By | December 12, 2015

So your knees hurt after squats? If this is you then you may want to consider the range of motion you use when squatsquatting. How low do you go? This is important due to the amount of pressure that is put on the knee throughout the movement.

The old belief was that going below parallel was much harder on the knees and could lead to all sorts of pain and problems, however this has changed due to much more recent studies. Squatting deeply was studied by the University of Texas’ Dr. Karl Klein in 1961 in which he found that deep squats (below parallel) had detrimental effects on the knees (1).  After this “proof” the American Medical Association positioned with Dr. Klein on deep squats being damaging to knee ligaments. This led to a very widespread belief, Doctors began to recommend squatting above parallel as well as athletic coaches.

Later, after the belief had already made its impact, flaws in the test published in 1961 were brought to light. One of Dr. Klein’s test subjects, Bill Starr NFL strength and conditioning coach, outlined basic flaws in the test that would have lead to inaccuracy in the results. Also, no other researchers were able to duplicate Klein’s results.

New Study Brings Change

In 2013 a study was performed to see whether deep squats lead to increased injury in the knees and lumbar spine. It was conducted by Hagen Hartmann, et. al. from the Department of Human Movement Science and Athletic Training, Institute of Sports Sciences at Goethe-University, Frankfurt am Main, Germany.

Judging from biomechanical calculations and measurements made on cadaver knee joints, the scientists found that the highest retropatellar compressive forces and stresses on the knees are at 90 degrees, or parallel. Increased flexion (deeper squats) leads to the wrapping effect which means that the load (weight) is distributed more evenly and there is force transfered with lower retropatellar compressive forces (2).

Claims that deep squats lead to chondromalacia, osteoarthritis, and osteochondritis were unproven.

In fact, quite the opposite was found. When working with the same load configuration in squats with less range of motion, such as half/quarter squats, supra-maximal weight loads actually increase likelihood of  degenerative knee changes and vertibre long term (2).


Squats are probably the most under-ranged exercise there is. What I mean is that this is usually the exercise where people avoid full range of motion like a plague. It could be due to the large increase in difficulty when going below parallel or just that it is difficult to judge how far you are actually going down when you cannot see for yourself.

Try your best not to cheat yourself. Going deeper is deeper leads to more muscle activation which means more muscle gains and of course healthier knees.

If you have knee problems try giving deeper squats a try for a month or two and see if there is any positive changes.


Comment below if you have questions or just anything to add.




(1) Klein K. The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee. J Assoc Phys Ment Rehabil 15: 6–11, 1961.

(2) Hartmann H, Wirth K, Klusemann M. Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Med. 43(10):993-1008, 2013.

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