The 1 Leg Squat Pattern – Assessment and Correction of Movement Dysfunction

By Dr Jason Gray BHK Dc MSc

The 1 leg squat test is a very effective and valuable screening tool when looking for the cause of problems in the pelvis, hip, and lower extremity. This test is especially important for runners or people who experience pain with walking or climbing stairs.

Here is the basis for this test….

When standing or squatting on 2 legs, each leg serves as a pillar of support for our trunk and pelvis. When standing or squatting on only one leg we lose the support under one side of the pelvis. This creates a tendency for the pelvis to fall towards the unsupported side, which causes a misalignment of the pelvis. As the pelvis forms the link between the trunk and lower extremity, a misalignment of the pelvis will in turn pull the spine and/or lower extremity out of the proper alignment as well.

Why does this matter?

To prevent joint and muscular strain the body must maintain the normal postural alignment of the pelvis and lower extremity during. This includes activities that require the body to be in a unilaterally supported position such as walking, running, or climbing stairs.  Under normal circumstances the muscles on the the posterior and lateral aspect of the stance leg hip will contract to keep these segments in their proper positions. (The key muscles are the gluteus maximus, medius, and minimus; and the piriformis and other deep external rotator group). So the 1 leg squat is actually an excellent functional test to assess the strength and coordination of this critical muscle group, and should be included when examining any pelvic, hip, knee, or foot/ankle problem.

The remainder of this article will look more in depth at the 1 leg squat squat pattern. Topics will include: 1) What constitutes a ‘normal’ 1 leg squat pattern; 2) What are the most common dysfunctional patterns seen with a faulty 1 leg squat, including the causes of these patterns; and, 3) What are the best ways to correct a faulty 1 leg squat pattern.

 The ‘Normal’ 1 Leg Squat Pattern – What Should a Squat Look Like


Assessment in the Lateral View – What is Normal?

Similar to the bilateral squat, the 1 leg squat is initiated with dorsiflexion of the the ankle, which allows the lower leg to rotate forward and the knee to translate forward over the toes. As this happens the knee and hip will flex and the trunk will adapt a slightly forward inclination, further accentuating flexion at the hip and helping to the keep the body’s centre of gravity balanced over the toes.

When assessing the 1 leg squat from the side view, the 1 leg squat should look similar to the bilateral squat, although it is expected that the overall range/depth of the 1 leg squat would be less. With the feet flat on the ground the thighs should be able to reach a least a 45 degree angle, the knees should be positioned directly over over the toes, and the trunk and lower legs should both be inclined forward and should be parallel to each other.


Common Problems Seen in the Lateral View

When assessing the 1 leg squat from the side view one of the most common problems seen is a position in which the knees passes too far in front of the toes at the bottom of the motion. This is often referred to as a patello-femoral shear pattern. This is often seen in conjunction with the trunk staying too upright so the that lower leg is inclined much farther forward compared to the trunk (remember, the trunk and lower legs should be parallel).

With this position the body is lowered more from the knee and ankle (these joints move too much), while the hip motion and force contribution is that under normal circumstances (this hip does not flex enough). With this pattern there is excessive load placed on the ankle and knee, causing the muscles surrounding these joints (the quadriceps and calf) to supply more of the muscle force needed to raise and lower the body in or out of the 1 leg squat. This this pattern is very common in people who suffer from anterior knee pain/ patellofemoral syndrome, as well as achilles tendinopathy. Common causes of this pattern often include a lack of flexibility of hip flexion or internal rotation, weak hip extensors, and sometimes weak trunk extensors (the body avoids forward inclination of the trunk to protect the back).

While less common, the opposite pattern in which the trunk flexes too far forward while the knee and ankle demonstrate reduced motion can also be seen. In this pattern the trunk incline angle is greater than that of the lower leg. Similar to the pattern described above, the areas of the body that move more than normal, in this case the hip and/or back, are doing more of the work. This makes them more susceptible to pain and overload, while the knee and ankle contribute less muscle force compared to normal. Common causes of this pattern include ankle dorsiflexion restriction, ankle/calf weakness, or quadriceps weakness.


Assessment in the Front View – What is Normal?

When looking at the 1 leg squat from the front the critical assessment point is to determine if the pelvis has remained level, and if the ankle, knee, and hip remain aligned over each other.  Determining if the lower extremity is held in the correct alignment is most easily assessed by looking at the angle formed by 1) the thigh and lower leg, and 2) the lower leg and the foot. Essentially, the alignment of the hip, knee, ankle, and foot observed during a relaxed, standing position should be maintained during the 1 leg squat. With the pelvis, sometimes it is easier to observe the position of the pelvis from behind by using the belt-line or waistband of the shorts as a reference point. Under normal circumstances the pelvis (or belt-line) should remain level, and should not twist or rotate to either side.


Common Problems Seen from the Front View

A common problem seen from the front view is a loss of pelvic stability during the 1 leg squat. This can be seen as either the pelvis dropping towards the floor on the unsupported side, or the pelvis sliding towards the stance leg. Both of these patterns hip abductors and/or external rotators (gluteus maximus, medius, and minimus, piriformis, inferior and superior gemelli, and obturator internus) to hold the pelvis and/or thigh in the proper alignment. This pattern is commonly seen with pelvic/sacro-iliac pain, hip pain, and knee problems. In some cases, the pelvis can often be seen to rotate towards or away from the stance leg. This is also a problem and represents a dysfunction of the hip musculature, but this is much less common that the pattern described above.

Another common dysfunctional pattern seen from the anterior view is the knee falling inwards as the body is lowered towards the ground. This is referred to a a knee valgus, or genu valgus position, and is also caused by a weakness in the posterior-lateral hip muscles. These muscles must contract to stabilize the hip joint and prevent the thigh from rotating inward as the body is lowered down. This position can stress the hip, knee, and foot-ankle complex, and is commonly seen with injuries to these areas. With respect to the knee, this valgus position will also create a twisting/rotational stress at the knee. Rotational stress can be particularly hard on the knee (the knee is great at bending forwards and backwards, but does not like to twist) and can will often be a contributing factor to common knee injuries such a patellofemoral pain syndrome and iliotibial band problems,.

Correcting Dysfunctional Movement Patterns

It is important we are able to perform functional movements such as the 1 leg squat pattern properly. Remember, the 1 leg squat pattern is repeated many times per day during walking, running, and climbing stairs, so a dysfunctional pattern can easily lead to the accumulation of micro-trauma and eventually pain and injury.

The key to correcting the 1 leg squat is identifying the specific muscle and/or joint problems , particularly at the posterior-lateral hip muscles, and first addressing those problems. In some cases this can often be done with specific stretches or exercises. In other cases the muscles and joints may be contain scar tissue / soft tissue adhesions. When this is the case these adhesions need to be released before the tissues will respond to stretches and exercises.  Active Release Techniques (ART) treatment works well for this (see our article on ART for more information). As the local problems are resolved and the hip, knee, and foot can all work the way they are supposed to, you can then start to train the squat and then then the 1 leg squat as part of your your rehabilitation or fitness routine, being careful to use proper form.