Fitness: Knees In or Out During a Squat? [Video]

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Fitness and strength coach Conrad Stalheim moderated a debate on the Breaking Muscle website between those who think having the knees in (valgus) is preferred, and those who believe knees out (varus) is appropriate in a loaded squat. On the varus side, physical therapist and coach Kelly Starrett was present, while the valgus side was supported by Bob Takano, Brendan Murray, Dan Green and a large number of Olympic weightlifters. While there is validity on both sides of the debate, Stalheim points out that the problem may not be whether one should squat with the knees in or out, but rather it is the poor communication between both sides that causes each to be misrepresented.

For example, coaches who advocate the valgus movement do not mean that the knee and hip joints are fully internally rotated like someone who just got kicked in the groin. Stalheim wrote that “knees in” does not mean that the toes are pointed out at 45 degrees while the knees buckle in to the point that they are touching. Likewise, the same can be said about knee varus, where the hip joints and knees do not externally rotate all the way out, as in a kung fu horse stance.

“Only very limited work have [sic] been done in the field of squatting among subject [s] with patellofemoral  pain,” said Michael S. Rathleff, Ph.D., from the Department of Health Science and Technology at Aalborg University in Denmark. “We published a study a few months ago that showed that subjects with PFP have a more medial pressure under the foot during single leg squat as well as drop jumps. The medial foot loading is likely a proxy of a more medial loading pattern of the lower extremity (valgus knee).”

Rathleff’s study, which was published in Knee Surgery, Sports Traumatology, Arthroscopy on March 2014, compared 23 young adults with PFP to 20 young adults without knee pain. The subjects were matched by age and gender. Sensors in the insoles of the shoes collected the amount of force placed upon the feet during a drop jump and a single-leg squat. The result showed that those with PFP tend to move their knees in during the drop jump, which was 22 percent higher than those without pain. In a single-leg squat test, subjects with PFP also had more pressure on the inside of the foot, which suggests they move their knees inward on this move as well.

“Another factor seems to be the forces going through the knee. A paper from Timothy Hewett’s group revealed that high knee abduction moment during landing increased the risk of developing PFP,” said Rathleff, refering to a study that was published in 2010 in Clinical Biomechanics. “Landing mechanisms are different from squatting technique, but I think some of the same mechanisms might be at play suggestion [sic] that frontal place motion is important, and one should not seek to overemphasize valgus movement at the knee during squatting.”

Hewett and his team wrote that biomechanical factors may not be the sole contributors to PFP. They mentioned that intrinsic factors, such as “anatomical, hormonal and potentially psychological parameters” may contribute to the onset of PFP, which were not controlled or investigated. If so, biomechanical factors may contribute some, but not the majority, of the cause of knee pain.


“Human knees don’t perform as well without the two fibrocartilage meniscus in between, which help distribute forces up to 70 percent,” explained licensed physical therapy assistant Ryan Crandall, B.S., in an interview with Guardian Liberty Voice, who gave a very detailed description to determine whether knees should go in or out during a squat. “The lateral meniscus is more mobile than the medial meniscus and is less prone to injury. Since the knee has a relatively shallow surface to work on, it requires stability from restraining ligaments as well as muscular power to help control and restrain motion.”

“Speaking of motion,” Crandall continued, “the knee moves three-dimensionally through several axes depending on the needs of the person moving, which will vary and depend on the terrain as well as what the upper body is doing. The medial side of the knee joint has been described as a ball-and-socket joint in which the surface motion moves by sliding and the lateral tibiofemoral joint as a joint that combines rolling, spinning, and countertranslation. For example, as someone moves from standing in full extension at the knee and progresses into squatting, the knee that bends the tibia will internally rotate relative to the femur. This motion occurs as the medial side of the tibiofemoral joint pivots and the lateral tibiofemoral joint moves posteriorly which is relative tibial internal rotation as mentioned above. Coming out of a squat will provide the reverse mechanism with the tibia externally rotating relative to the femur upon full extension.”

Since the knee is not a pure hinge joint, Crandall added that the human body is very capable of adapting to the environment, allowing the knees and other joints to move in more ways than most trainers would think they can move. “Would it matter much if the toes are in or out? Would it matter if the knees are shoved in or out? Would it matter if one leg is slightly in front as in a stride stance squat? There is very little evidence to show that there is a preferable way,” said Crandall, owner of Post Rehab 4 U in Albuquerque, New Mexico, who then demonstrated the versatility of the knees, ankles and hips in various squat patterns.

Unless they have pain or some sort of previous injury or muscle or joint disease, fitness professionals and their clients do not need to worry much about whether squats should be done with the knees in or out. “If you have been squatting with ‘knees slightly in’ technique for several years without issues, you can continue, but I would never recommend anyone to change their technique to use more valgus motion at the knee during the concentric phase of the squat,” Rathleff suggested.

By Nick Ng


Breaking Muscle
Sports Medicine
Interview with Ryan Crandall, PTA
Interview with Michael Rathleff, Ph.D.
Knee Surgery, Sports Traumatology, Arthroscopy
Clinical Biomechanics