physicians condemn the squat,
citing how destructive they are to the knees, despite scientific
studies and millions of personal experiences to the contrary.
One sports medicine doctor explained to me why squats were considered
to be bad for the knees. He was actually telling me this between
his sets of squats! Since sports medicine doctors only see people
with injuries one can guess why they may have developed this
belief. The individuals they treat certainly do not constitute
a random sample, let alone a representative population which,
as any scientist knows, is essential to even attempt to formulate
The NSCA position statement notes:
"Some reports of high injury rate may be based on biased
samples. Others have attributed injuries to weight training,
including the squat, which could have been caused by other factors.
Injuries attributed to the squat may result not from the exercise
itself, but from improper technique, pre-existing structural
abnormalities, other physical activities, fatigue or excessive
An early study suggested deep knee bends with weights (squats)
were hazardous to the ligamentous structures of the knee. Later
studies conclude squats improve knee stability if the lifting
technique does not place rotary
stresses on the knee (Fleck and Falkel, 1986). The NSCA state:
"Squats, when performed correctly and with appropriate
supervision, are not only safe, but may be a significant deterrent
to knee injuries."
to propaganda, prominent weight training authorities demonstrate
the squat with the knees flexing forward at the same distance
as the hips flex backwards. Fredrick Hatfield, Ph.D., the first
man to squat over 800 lbs, recommends the knees to extend over
the feet with the back more upright for quadriceps development.
Training for Young Athletes" by Steven
J. Fleck, PhD and William
J. Kraemer, PhD, illustrate parallel squats with the knees
extending beyond the feet (knees moving forward with same magnitude
as the hips moving backwards).
Torque force is necessary for the muscles and joint structures
to adapt to the respected overload. If the knee does not travel
forward during the barbell squat, the quadriceps muscles (ie:
knee extensors) are not significantly exercised. On the other
hand, injury may result if the knee or lower back experience
greater torque forces than to what they are accustomed.
Fry et. al. (2003) examined the hip and knee torque forces
of variations of parallel barbels squats and concluded appropriate
joint loading during this exercise may require the knees to move
slightly past the toes.
Torque through the hip active not only activate the Gluteus
Maximus and Adductor
Magnus, but also the three heads of the Hamstrings
which cross both the hip and knee. Torque through the knee activate
the Quadriceps. Through
the knee, the dislocating forces of the quadriceps are countered
by the stabilizing forces of the hamstrings. See diagram of the
countering forces next to Hamstring
Weakness. Also see Knee
During the execution of a barbell squat, the knees and the
hips travel in opposite directions away from the foot, or away
from the center of gravity. Torque forces increase both through
the knee and hip joints as the exerciser desends. The greatest
torque forces are experienced when initiating the rise out of
the bottom position.
Try this simplified qualitative method in determining relative
torque forces in the knee and hip joints. First take a photograph
of the barbell squat in a full descent with a perspective perpendicular
to the joints plane. Draw a line of force through the resistance
on its center of gravity, straight up
and down, parallel to the force of gravity. Gravity acting on
both the body mass and added mass (barbell) contribute to the
resistance. Incidentally, compression forces act upon the joints
during the squat stance. On the barbell squat, the center of
gravity is over instep (between the forefoot and heel). If it
is not, the individual will fall over, toward the center of gravity.
Now draw three seperate horizontal lines, perpendicular to
the line of force. from each joint articulation (ankle, knee,
and hip) to the line force. If the image is not exactly viewed
from the side, the "horizontal" lines can be drawn
in perspective to picture as shown. Once the diagram is complete,
a relative comparison can be made on the torque forces of the
hip, knee, and ankle.
Typically the torque forces in the barbell squat are slightly
greater for the stronger hip joints as compared to the knee joint
although both the knee and hips travel in opposite direction
away from the line of force. Generally speaking, during a powerlift
type squat (bar lower behind the shoulders and a wider stance)
the knee does not travel forward as far as a bodybuilding
type squat. The hips typically travel back further with the
torso bent forward on a powerlift type squat. This emphasizes
the stronger hip extensors and adductors and consequently reduces
knee extensor involvement. Knee torque is further reduced by
a wide stance.
Also see Qualitative
Torque Analysis (comparison image to above)
The practice of adopting foot rotation to selectively strengthen
individual muscles of the quadriceps is not supported by the
literature (Boyden 2000; Signorile 1995). Knee
rotation during the squat can increase the risk of injury
(Fleck and Falkel, 1986). Signorile, et. al. states:
"Extreme outward toe point greatly reduces stability,
it does not allow the proper drift of the hips as the lifter
descends... Extreme inward toe points are equally dangerous,
coupling the same problems of stability, base size and lower
body drift with the added danger of bringing the knees together...this
movement would place high stress on all connective tissue."
Full (Deep) Squat
(1996) illustrates the safe position of a deep squat with the
knees extending beyond the toes. Kreighbaum explains how a deep
squat can be performed little chance of injury to the knee.
The variables of concern:
- speed of descent
- size of calves and thighs
- strength of the controlling muscles
The primary danger to the knee occurs when the tissues of
the calf and thigh press together altering the center of rotation
back to the contact area creating a dislocation effect. The danger
of knee injury in this situation may be prevented if either of
the following factor are present:
- center of gravity of the body system is kept forward of the
altered center of rotation
- muscles of the thigh are strong enough to prevent the body
from resting or bouncing on the calves.
Kreighbaum concludes the deep squat is of little danger to
the knees unless these variables and factors are disregarded.
Certainly only a limit type of athletes and performers may have
a the need to perform a full squat. Olympic weightlifters commonly
bounce out of a full front squat with near maximum resistances
during both the Clean
& Jerk and Snatch.
Incidentally, the wide stance during an Olympic-style
squat further reduces knee torque forces. Reportedly, those
proficient in the Polzunec movement in the style of the Ukrainian
national folk dance appear to experience few orthopedic problems
(up until middle ages where their incident of orthopedic problems
seem to be no greater than the general population) despite their
ability to perform a seemingly contraindicative movement for
decades; body upright, bounding from one leg to the other in
the deepest squat position. Also see Over
During the lower portions of the deep squat the lower back
may flex if hip
flexibility is inadequate. The risk of low back injury is
increased if the muscles of the lower back are not strong enough
to support the flexed spine or the joint structures have not
progressively adapted to such a stress. Flexibility exercises
can be performed if hip flexibility is insufficient for deep,
or full, squats. See Full
Squat Flexibility and Deep
The squat can decrease knee injury (NSCA) and increase
leg power (Adams, 1992) when implemented into a sound strength
and condition program. Early in the off season, squat training
will develop the foundation for more sports specific training,
such as plyometric work. See Conditioning
The strength and conditioning coaches may choose from a variety
of squat movements. The type(s) of squat(s) prescribed should
prepare the athlete for specific biomechanical stresses demanded
by the sport as well as other conditioning exercises. Coaches
commonly prescribe the powerlifting
squat (wide stance, bar low on back, little knee torque)
at exclusion exercises with greater knee torque, namely the Olympic
style front squat and the bodybuilding
style squat. Coaches cite the importance of hip extension
strength and power. The Glutes are after all the most powerful
muscles of the body.
Exercises that are most beneficial for sports performance
are generally those that are similar to the type of forces and
counter forces experienced on the playing field. See Training
Specificity and Resistance
Training for the Reduction of Sports Injury. The coach must
consider the unique biomechanic requirements of the sport, as
well as the requirements of each athlete's position. The hip/knee/ankle
torque ratio should be similar to actual biomechanics experienced
on playing field. Motor skills such as blocking, jumping,
leaping, etc. generally involve greater knee and ankle torque
than what is required of the traditional 'powerlifting' squat.
The 'bodybuilding' squat and power
training such as Olympic-style weightlifting and plyometrics,
require a higher ratio of knee/ankle versus hip torque than the
Conversely, some coaches cite knee injuries as a reason to
avoid any other squat than the 'powerlifting style' squat when
in fact the risk of knee injury may be attributed to other factors.
See squat safety above and Exercise
of Injury and Sports
If the body has not adapted to a greater
torque force, injury can result. It is not necessary to avoid
the torque force if the muscles and joint structures can adapt.
See adaptation criteria.
Of the hip and knee joint, the knee is more vulnerable to injury
than the hip due to structural and functional differences. Certainly,
if an individual has had a history of knee pain associated with
these types of movements, the squat can be modified to to place
more torque on the hip and consequently less on the knee joint.
Based on the above analysis, this can be accomplished two ways.
Simply, by not squatting down all the way (e.g. 90°) both
the knees and hip do not experience as great of torque forces.
Although, this decrease is may be off set by the tendency to
add more weight to the exercise. Alternatively, by bending at
the hip more than the knee, the knee will travel forward less,
as in the powerlifting type squat. Recall, the quadriceps will
not be exercised as intensely since there is less torque on the
knee joint. In addition, since balance must be maintained over
the feet, bending over not only transfers more torque to the
hips, the torque forces through the spine (lower back) increase,
another vulnerable joint for some. Certainly a compromise must
be made to evenly distribute the torque force between the knee
and the hip/lower back, particularly when both the knees and
lower back are healthy.
If the ankle is not flexible enough
to allow the knee to travel forward sufficiently, the back will
need to be bent forward more to maintain the center of gravity
within the foot base. Consequently the lower back with be subjected
to greater torque forces. Squatting with the feet wide apart
can alleviate part of the problem, allowing the back to be positioned
more upright. This solution does not, however, distribute equal
stresses on the quadriceps and glutes as would be possible with
Until flexibility can be restored, a temporary solution is
to elevate the ankles on a board or platform. This will allow
the knees to travel forward the same distance as the hip travels
backwards. Elevating the heels may present a risk to individuals
with adequate ankle flexibility who have not adapted to greater
torque forces through the knee. In which case, the knees can
potentially travel forward more than what they are accustomed
to. Even when elevating the heels with insufficient ankle flexibility,
resistance should begin light and progress only 5-10% every workout
until a true workout weight is achieved, so joint adaption can
Obviously, individuals who are at a higher risk for specific
types of knee pain may choose to perform the powerlifting
squat while avoiding certain exercises specifically designed
to emphasize the quadriceps' involvement by increased knee torque
hack squat, leg
extension). Likewise, individuals who are prone to particular
types of lower back problems may favor the weighted
squat or leg
press while avoiding certain exercises specifically designed
to lower back involvement by increased lower back torque (e.g.
- Boyden G, Kingman J, Dyson R, (2000). A comparison of quadriceps
electromyographic activity with the position of the foot during
the parallel squat. J Strength Cond Res. 14(4): 379-382.
- Fleck, S.J. and Falkel, J.E. Value of Resistance Training
for the Reduction of Sports Injuries. Sports Medicine,
3, 61-68, 1986.
- Fry AC, Smith JC, Schilling BK. Effect of knee position on
hip and knee torques during the barbell squat. J Strength Cond
Res. 2003 Nov;17(4):629-33.
- Hatfield, F.C. (1989). Power: A Scientific Approach, Contemporary
Books, pg. 158.
- Kraemer, W.J., Fleck, S.J. (1993). Strength Training for
Young Athletes, Human Kinetics.
- Kreighbaum, E., Katharine, B.M. (1996). Biomechanics; A Qualitative
Approach for Studying Human Movement, Allyn & Bacon, 4, Pgs
- National Strength and Conditioning Association. The Squat
Exercise in Athletic Conditioning, NSCA Position Statements.
- Signorile JF, Kwiatkowksi K, Caruso JF, Robertson B, (1995).
Effect of foot position on the electromyographical activity of
the superficial quadriceps muscles during the parallel squat
and knee extension. J Strength Cond Res. 9:182-187.
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