Off the axis → a joint wears on one side: why "practice that never hurts" can still grind a joint away over years

Joint cartilage is one of the smoothest surfaces in the body, but it has one fatal weakness: it has no blood supply of its own. It lives on joint fluid 'pumped' back and forth every time we move the joint — movement brings the nutrients in and carries the waste out.

• On-axis load + movement through the full range = a good pump = cartilage fed.
• Off-axis load, pressing one point continuously = mechanical destruction, and at the same time it OBSTRUCTS the nutrition at exactly the spot being crushed.

This is why cartilage wear happens silently and is very nearly irreversible: once it wears rough as sandpaper → the joint space narrows → bone spurs form → and finally bone meets bone (osteoarthritis).

Students tend to think "what harm can one bad repetition do?" Quite right — one does no harm. The problem is:

• The off-axis load repeats every session, accumulating over thousands of repetitions.
• Each one sits below the threshold of pain, and the body records it in silence — until a 'last straw' threshold is reached and it breaks out, often after many YEARS.

The stress–strain curve shows it plainly: each off-axis load may still sit inside the 'elastic' range (nothing broken), but repeated often enough the accumulated micro-damage pushes the tissue gradually into the failure range.

What this gives you: this is the answer to "why did a student practising properly for ten years only start to get hip pain now". They did not practise carelessly one day — one small misalignment was multiplied tens of thousands of times. Your job is to break the spiral on its first turn.

Lotus needs a GREAT deal of external rotation at the hip. The hip (a ball and socket) rotates a long way; the knee (a hinge) barely rotates at all.

• If the hip lacks the range of external rotation, the practitioner usually 'borrows' that rotation from the KNEE without realising it.
• The knee is twisted → the surfaces no longer fit → force is distributed abnormally → damage to the medial meniscus and the medial collateral ligament.

The general lesson: each joint does its own job. Take the full rotation FROM THE HIP (the ball joint) to PROTECT the knee (the hinge). Spread the rotation through the whole leg instead of dumping it into the knee alone.

Coming next: the knee is only one link. Immediately above it, the spine plays by this same off-axis rule — but in a way that is more treacherous still.

The answer to a very practical question: are twists in yoga bad for the discs?

• The lumbar segment has the five largest vertebrae, but is very nearly not designed to rotate (big spinous processes, facet joints oriented to block rotation).
• A great many lower-back injuries in yoga come from a twist FORCED through the lumbar spine instead of through the thoracic spine — which is far more mobile in rotation.
• A twist at a segment that should not rotate → the facet joints and discs take shear and torsion off their axis → over time this tears the annular fibres and grinds one side of the facet surfaces.

Measurable correction cue: lead the twist from the chest upwards, keeping hips and lower back stable ("hips still, chest turning"); create length along the spine's axis BEFORE turning, to "protect the discs".

An unexpected link: the hamstring group attaches to the sitting bones.

• Over-tight hamstrings pull the pelvis into a posterior tilt → the natural lumbar curve is lost.
• Without its physiological curve, the spine → dumps uneven pressure on the lowest disc, especially L5–S1 (the most vulnerable segment).

What this gives you: when a student folds forward and the back rounds into a hump, the root is usually NOT in the back but in tight hamstrings. Correcting from the hamstrings (a slight knee bend, tilting the pelvis from the hip) brings the spine back on to its axis.

Coming next: but knee and spine alike stand on a foundation. If that foundation is off, every alignment above it is meaningless — and that foundation is the foot.

Because alignment runs FROM the foot UP, this is where you have to correct first:

• "The four corners of the foot" touching the ground evenly — inner heel, outer heel, base of the big toe, base of the little toe; load them evenly so force passes straight through the centre of the ankle.
• Lift the inner arch by pressing the OUTER edge of the foot firmly down (recruiting the peroneal group) — the antidote to a foot collapsing inward.
• Tibialis anterior and posterior are the main pillars holding the arch — weak, and the arch drops.

The priceless combined cue — "shins in, thighs out": draw the two shins gently inward (adduction, the peroneals) while turning the two thighs outward (hip abduction, gluteus medius). For most people this pair of instructions puts the knee back on its anatomical plumb line — usable as a therapeutic tool in almost every standing pose.

The top end of the chain follows exactly the same principle:

• Ideally the head of the femur sits 'full and even' inside the socket.
• If it is continually pushed towards one side, or continually rotated one way and back, the cartilage lining the hip joint will wear UNEVENLY.

How to protect it: move the hip joint in every direction (flexion, extension, abduction, adduction, internal and external rotation) and balance the opposing actions so the femoral head settles into the CENTRE of the socket. Gluteus medius and the external rotators of the hip are the chief 'axis-keepers' here.

Coming next: which means the teacher's whole task folds into one question — how do you get the load to pass through the centre of all these joints, in every different body?

A common mistake: thinking alignment is only about 'getting into the right position' as you enter the pose.

• Under load, the joint will DRIFT off its axis unless the stabilising muscles (the fixators) are recruited and held for the whole duration of the hold.
• So a teacher does TWO things at once: (1) correct the GEOMETRY (knee over ankle, joints in one line, weight even across both legs) and (2) teach the ACTIVATION that holds the axis (grip the thighs, press the ball of the foot, "shins in, thighs out", engage the core).

What this gives you: this is the line between 'making a shape' and 'practising safely'. The student has to feel which muscle is holding the axis, rather than hanging on their ligaments.

A mark of professional maturity that a good teacher needs:

• Alignment "encourages optimal function and prevents injury" — but what counts as correct changes from person to person and from day to day.
• Every person's bone structure differs (the angle of the femoral neck, the shape of the socket). Forcing one textbook mould can sometimes push that very joint OFF its own natural axis.
• A hands-on adjustment made to fit a general mould can do harm rather than help.

The measurable landmarks above are the common standard — a solid place to begin. Reading the individual structure of EACH student (and fitting the general mould to that body) is a deeper layer of skill that takes much more practice — but its foundation is still the general principle you have just taken in.

The golden rule: the final aim is not "a pose that looks like the photograph", but "force passing through the centre of THIS body's joints". Observe and adjust for the individual; do not stamp out a template.

Come into Warrior II and look down at the front knee:

• Deliberately let the knee fall inward past the big toe (valgus) → feel the OUTER compartment of the knee being squeezed tight while the joint space on the inside is pulled open, and the arch of the foot drops with it.
• Now bring the knee back in line with the second toe and press the outer edge of the foot down → feel the load 'spread evenly' through the whole joint, and the knee steadier.

That is precisely the sensation of 'load through the centre' you need to teach students to recognise.

Stand in Tadasana, feet parallel:

• Lock the knees into full extension, pushing them back → the sensation of 'leaning' on the joint, with the thigh muscles slack.
• Release into a micro-bend, press the ball of the foot lightly down, grip the thighs → the sensation of muscle starting to work, the knee 'alive' and stable.

That difference is exactly the line between hanging on your ligaments and holding the axis with muscle.

Stand on one leg (Tree, Vrksasana) or simply stand normally:

• Deliberately drop the weight on to the inner edge of the foot and let the arch collapse → notice the knee tending to draw inward and one hip dropping.
• Lift the inner arch and spread the load across the four corners of the foot → feel the knee straighten of its own accord and the hips come level.

You have just felt the 'kinetic chain' in your own body: correct at the FOUNDATION and the whole tower straightens with it.