Why can't I stand on one leg!

Julia Williams • 15 February 2026

Why is more difficult to stand on my right leg?

A common question in clinic

Patients often comment that they find it more difficult to stand on one leg (usually the right) than the other.

Even more frequently, I notice the asymmetry and instability on normal standing examination.

They have normally complained of some kind of back pain and also have a history of knee and hip issues.

Essentially, their leg isn't staying centred because the forces acting on it are winning against the structures meant to stabilize it.

On strength testing, we often find a major weakness or lack of activation of the gluteus maximus, and the other hip extensors - however many squats you do, they never seem to get any stronger.

The Sacro-iliac Connection

Sacroiliac dysfunction is a major structural cause of instability of the whole body, and is incredibly common, not least due to most of us being 'right footed' - we have an inherent preference for using the right foot to, for example, kick a ball.  And interestingly, even most left-handed people are also right footed!


This asymmetry predisposes us to a dysfunction of the sacroiliac joint, usually consisting of a right rotation and counter-nutation of the sacrum.


The relationship between the sacroiliac joint (SIJ) and the hip extensors:

  • Because the gluteus maximus attaches directly to the ligaments of the SIJ, the position of the joint dictates how well this muscle can fire.


The SIJ (sacroiliac joint) moves in a subtle rocking motion called nutation and counter-nutation.


1. SIJ Nutation (Stability for Extension)

Nutation occurs when the top of the sacrum tips forward relative to the ilium (pelvic bones). This is the same movement as leaning or arching your body backwards.

  • The gluteus maximus is attaches to the dorsal sacroiliac ligaments.
  • When the sacrum is nutated, the gluteus maximus has a stable anchor point to pull from.
  • this allows for maximum force production during hip extension.
  • If your SIJ is 'stuck' in counter-nutation (sacrum tipped back), the gluteus maximus often becomes neurologically inhibited because its 'anchor' is unstable.
  • this is often only the case on one side of the sacrum, usually the right.

2. Asymmetry (SIJ Torsion)

If one side of the SIJ is nutated and the other is counter-nutated (a pelvic torsion):

  • You will experience asymmetrical glute firing.
  • one leg will feel powerful during hip extension (the nutated side), while the other may feel 'disconnected' or weak. This is a common culprit behind chronic one-sided glute or hamstring pain.

Nutation vs. counter-nutation of the sacrum

Left: nutation = sacral base moves forwards/coccyx moves backwards = lumbosacral extension = increase in lordosis

Right: counter-nutation = sacral base moves backwards/coccyx moves forwards = lumbosacral flexion = decrease in lordosis

N.B. both movements can occur in forward or backward bending of the body depending on the relative positioning of the pelvis. E.g. bending forwards can take place with either a concave lumbar spine (nutation) or  a convex lumbar spine (counter-nutation)

The sacrum should 'float' between the ilia so that the ilium is not dragged forwards or backwards. 'Locking' or a 'fixation' of a sacroiliac joint (usually the right) means that the ilium sticks with the sacrum. This leads the sacrum to rotate and causes local irritation of the sacroiliac ligaments as well as disrupting the anchor points of muscles such as the gluteus maximus, piriformis and hamstrings.

Muscle attachments at the sacroiliac joint

The hamstrings attach to the sacrotuberous ligament of the pelvis. This means:

  • when the sacrum is in nutation, the sacrotuberous ligament is under tension
  • therefore the hamstrings, specifically the long head of biceps femoris tends to be stretched and under high tension.
  • can make them overactive and prone to strain.


The gluteus maximus attaches to the ilium, sacrum and the dorsal sacroiliac ligament. This means:

  • disruption of the normal floating of the sacroiliac joint
  • inhibits gluteus maximus activation.

Testing the hip extensors - gluteus maximus

 When you move into a 'frog leg' position—combining hip external rotation, abduction, and knee flexion—the mechanics of hip extension shift significantly.


In a neutral position, your gluteus maximus and hamstrings share the load of extension. However, in this specific orientation, the hamstrings are 'disarmed' due to active insufficiency, forcing the glutes and specific adductor fibers to do the heavy lifting.

Why?

  • Mechanical Advantage: The gluteus maximus is not only a powerful extensor but also a primary external rotator.By pre-rotating the hip, you place the muscle fibers in a shortened, highly active state.


  • Why it dominates: Because the knees are bent, the hamstrings (which also cross the knee) are shortened, making them less effective at generating force at the hip. This forces the gluteus maximus to take on nearly all the work of extension.
One of the best ways to test gluteus maximus is to inhibit the hamstrings by externally rotating the thighs.
The next stage is to use a single leg pelvic lift, still with the lifting leg externally rotated.

What to do about it!

It may be possible for you to relieve your own sacroiliac dysfunction using a simple right sided lunge position. However, an osteopath will also be able to assess and treat this problem, often very easily and with 'miraculous 'results!

I also use the patient's breathing as a vital part of my method of realigning and stabilising the sacroiliac joints.

Here's why!


Breathing - the hidden stabiliser of the SI joint

You can think of your core as a pressurized canister: the diaphragm as the lid, the pelvic floor as the base, and the transverse abdominis forming the walls.


If the 'lid' (breathing) isn't working correctly, the 'base' (where the sacroiliac joint lives) cannot stabilize, causing the hip extensors, your glutes and hamstrings to lose their foundations.

1. The Intra-Abdominal Pressure (IAP) Effect

When you inhale deeply into your belly (diaphragmatic breathing), the diaphragm moves downward. This increases intra-abdominal pressure (IAP).

  • This pressure pushes against the spine and the inside of the pelvis, forcing the sacrum into that stable nutation we discussed.
  • High IAP creates a rigid 'pillar' that allows the Gluteus Maximus to contract with maximum force. This is why powerlifters take a massive belly breath before a squat.

2. The Diaphragm-Psoas Connection

The diaphragm and the iliopsoas (the glute-inhibiting hip flexor) are anatomically linked via a piece of connective tissue called the medial arcuate ligament.

  • Chest breathing: If you breathe shallowly into your chest, the diaphragm never fully drops. This can keep the psoas in a state of constant tension/shortness.
  • As we know, a tight psoas inhibits the glutes through reciprocal inhibition. Simply learning to breathe into your lower belly can "reflexively" relax your hip flexors and let your glutes work.

3. The Pelvic Floor Synergy

The pelvic floor muscles attach to the same bones that form the SI joint.

  • As you exhale, the pelvic floor and the deep abdominals should naturally lift and tighten.
  • This 'co-contraction' provides the final squeeze that locks the SIJ.
  • Without a proper exhale during the 'work' phase of an exercise (like the upward part of a glute bridge), the SIJ remains 'loose', and the hamstrings will likely cramp as they try to compensate for the instability.


The Stability Chain

Diaphragmatic Breath → Increased IAP → Sacral Nutation (SIJ Stability) → Glute Activation


If any link in that chain is broken, you'll likely feel tight hamstrings or weak glutes regardless of how many squats you do.

Other causes of leg instability

There are of course, other factors that may lead to leg instability:

1. Hip Abductor Weakness (The "Trendelenburg" Effect)

This is the most common culprit. Your Gluteus Medius and Gluteus Minimus are responsible for keeping your pelvis level when you stand on one leg.

  • The Chain Reaction: If your hip is weak, your pelvis drops on the opposite side. To keep from falling over, your trunk shifts over the standing leg.
  • The Result: This shift moves your Center of Mass (COM) to the outside of the knee, pushing the joint into a bowed position.


2. Ankle and Foot Mechanics

What happens at the floor dictates what happens at the knee.

  • Over-supination: If you have high arches or an "inverted" foot, your weight stays on the outer edge of your foot. This naturally drives the knee outward.
  • Stiff Ankle: If your ankle lacks dorsiflexion (the ability to pull your toes toward your shin), your body might compensate by "bowing" the knee to find a path of least resistance during movement.


3. Glute Max & External Rotator Weakness

While the side of your hip (Glute Medius) handles the levelness of your pelvis, the Gluteus Maximus and deep rotators control the rotation of your thigh bone (femur).

  • The Collapse: If these muscles are sleepy, your thigh bone rotates inward and slides toward the midline. Since your foot is fixed on the ground, the knee has no choice but to buckle inward.


4. Foot Pronation (Flat Feet)

If your arch collapses or your ankle rolls inward (over-pronation), it creates a "bottom-up" effect.

  • The Chain Reaction: As the arch drops, the shin bone (tibia) rotates inward, which forces the knee into a valgus position. It’s like the foundation of a house shifting; everything above it tilts.


4. Quadriceps Imbalance

If your outer quad (Vastus Lateralis) is much stronger or tighter than your inner quad (Vastus Medialis / VMO), it can pull the kneecap and the joint alignment toward the midline during weight-bearing.


5. Tight Adductors (Inner Thighs)

If your inner thigh muscles are overactive or "short," they act like a tight bungee cord, constantly pulling your knee toward the center of your body.


6. Structural or Ligamentous Laxity

Sometimes the issue is "hardware" rather than "software":

  • LCL Laxity: If the Lateral Collateral Ligament (on the outside of your knee) is overstretched or injured, it can’t pull the joint back into alignment.
  • Meniscal Issues: A loss of cartilage in the inner (medial) compartment of the knee can cause the joint to collapse inward, making the outward bow look more prominent.

7. Neuromuscular Control

Sometimes your muscles are strong enough, but your brain hasn't "mapped" the correct movement pattern. This is common after an old injury where you learned to compensate by shifting your weight to avoid pain.

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