When a knee hurts, almost everything gets examined except the joint directly below it.
The knee gets assessed. The hip usually gets a look, since the hip and knee connection is reasonably well known. The ankle frequently gets nothing at all.
Which is a gap, because the ankle determines a great deal about what the knee has to do, and the restriction involved is extremely common and entirely modifiable.
What Your Ankle Is Supposed to Do
The movement that matters is called dorsiflexion. It is your ability to bring your knee forward over your foot while your heel stays on the ground.
You need it constantly:
Walking, as your body passes over the planted foot.
Going down stairs, where the demand is considerably higher than going up.
Squatting, where it determines how deep you can go with heels down.
Landing, where the ankle absorbs the first portion of the force.
And walking downhill, where it is required repeatedly.
When you do not have enough, the movement has to come from somewhere else. That is the whole mechanism.
What Happens at the Knee
Research examining this has found a fairly consistent picture.
A study of female collegiate soccer players assessed ankle dorsiflexion flexibility alongside landing mechanics during a drop vertical jump.
Those with less ankle dorsiflexion showed greater peak knee abduction moments, greater peak knee abduction angles, and less knee flexion during landing.
In plain terms: restricted ankles landed with the knee collapsing inward more and bending less. Those are the two patterns most associated with knee injury.
The authors concluded that dorsiflexion flexibility may serve as a useful clinical measure to predict poor landing postures, and described it as a modifiable factor.
Work in people with kneecap pain has found something similar. Less ankle mobility was associated with greater inward knee collapse and greater hip adduction during single leg squatting, with the authors suggesting that improving ankle dorsiflexion could reduce dynamic knee valgus.
And the proposed mechanism makes sense. During landing, if the ankle cannot allow the shin to travel forward, the force has to be absorbed elsewhere, and ground reaction forces rise.
There is also evidence linking reduced dorsiflexion to patellar tendon problems in jumping athletes.
The Honest Caveat
This is worth stating, because the relationship is not as clean as some coverage suggests.
Not every study agrees. Research comparing recreational female runners with and without kneecap pain found that ankle dorsiflexion mobility and dynamic knee valgus did not differ between the groups.
Which tells you something useful. Restricted ankles are associated with unfavorable knee mechanics in several studies, and that does not mean every person with a stiff ankle has knee pain, or that every knee problem is caused by an ankle.
The sensible position: ankle mobility is one modifiable factor worth checking in someone with knee pain, particularly if the pain is related to squatting, landing or stair descent. It is not a universal explanation.
Test Yourself
The knee to wall test.
Stand facing a wall. Place one foot on the ground with your toes a few inches back from the wall. Keeping your heel flat on the floor, drive that knee forward to touch the wall.
If you can touch it comfortably, move the foot back and try again. Keep moving back until your knee can only just reach the wall with the heel staying down.
Measure the distance from your big toe to the wall.
What matters most:
The comparison between sides. A clear difference between your two ankles tells you considerably more than the absolute number.
And a commonly used benchmark is around four inches, though normal range varies between individuals.
What usually produces a restriction: previous ankle sprains, Achilles problems, calf tightness, time in shoes with an elevated heel, and simple disuse.
That first one is the most common and the most overlooked. A high proportion of people have sprained an ankle at some point, a large proportion of those never had it properly rehabilitated, and reduced dorsiflexion is one of the lasting consequences.
The Knee Problems This Contributes To
Kneecap pain, particularly with stairs, squatting and prolonged sitting.
Patellar tendon pain, given the association with reduced dorsiflexion in jumping athletes.
General anterior knee pain with squatting or lunging.
And it is a factor in the landing mechanics associated with more serious knee injury risk.
A recognizable pattern: somebody who cannot squat deeply without their heels lifting, who compensates by letting their knees travel inward, and whose knee pain is worst with stairs and squats.
What to Do About It
Mobility work, targeted at the actual restriction.
Calf stretching with both a straight and bent knee, since the two heads of the calf respond differently and a bent knee version targets the deeper muscle.
Knee to wall drills, performed as repeated movement rather than a held stretch, progressing the foot further back over weeks.
Ankle joint mobilization, where the restriction is at the joint rather than the muscle, which is something an assessment identifies.
And consistency. Short sessions most days beat occasional long ones.
Then strength through the new range. Range you gain and do not use is range you lose again. Calf raises, loaded squats progressing in depth, and step downs all load the ankle through the range you have opened up.
Plus the knee and hip work, because the ankle is one contributor rather than the whole picture. Quadriceps and hip strength both matter and are frequently involved.
A Practical Note on Footwear
Worth mentioning because it is a quick adjustment.
A shoe with a higher heel to toe drop reduces how much ankle dorsiflexion you need for a given task. That can make squatting and stair descent more comfortable in the short term, which is occasionally useful during a flare.
It also means you are working around the restriction rather than addressing it, so it is a temporary measure rather than a solution.
When Knee Pain Needs Assessment First
Seek prompt assessment for:
A knee that locks or will not fully straighten.
A knee that gives way repeatedly.
Significant swelling, particularly if it came on within hours of an injury.
Inability to bear weight.
Pain following a specific injury with a pop.
Numbness, tingling or weakness in the leg.
And seek same day care for a knee that is hot, red and swollen, especially with fever.
Also worth assessment: persistent ankle stiffness following an injury, particularly if the ankle also feels unstable or gives way, since that combination points to an incompletely rehabilitated sprain.
Get the Whole Chain Looked At
If your knee has been treated in isolation and it has not resolved, the joints above and below are worth examining before concluding that nothing works.
Shiraj Physio offers a free discovery visit at no cost and no obligation. You will get a thorough assessment of your knee, hip, ankle and movement, a clear explanation of where the problem is actually being generated, and a plan that targets it rather than only the place it hurts.