KneeSchool/Clinical Examination Academy/Y Balance Test
Y Balance Test
Page 4.21.5 · Functional Testing · examination page
A reaching test done slowly on one leg, which measures control rather than power and is the only test in the battery that does.
The same topic at 4 depths
Each tier deepens the one below it and never repeats it. Choose the level you want.
Y Balance Test
Choose a depthFor Medical Students
What It Tests
The Y balance test asks the patient to stand on one leg and reach as far as possible with the other foot in three directions, so it measures single limb control through range. 4.21.1 covers the single leg squat.
The examination is comparing the reach distances in each direction between the two sides. 4.5.7 covers dynamic alignment.
It matters because control through a slow movement is a different ability from power, and a knee can have one without the other. 4.21.2 covers the single leg hop.
How It Is Performed
Confirm the patient can stand on the limb without pain, which is the only prerequisite. 4.7.9 covers the functional range.
Set up the three reach directions, which are forwards and two backwards diagonals.
Ask the patient to stand on one leg and reach along each direction with the free foot, touching lightly without transferring weight.
Record the furthest reach achieved in each direction, and repeat for the other side.
Watch the stance knee during the reach, since control failures show there rather than in the reaching limb. 3.12.7 covers dynamic valgus.
Invalidate any attempt where the patient puts weight on the reaching foot or loses balance.
Compare the directions as well as the sides, because the pattern of deficit is informative. 4.1.4 covers the structured approach.
What a Positive Means
Similar reaches in all three directions on both sides is the normal result.
A reduced forward reach indicates limited knee flexion tolerance or quadriceps control. 4.7.4 covers the flexion assessment.
Reduced backward diagonal reaches indicate hip and trunk control deficits more than knee ones. 4.4.5 covers the Trendelenburg gait.
A deficit in one direction only is more informative than a uniform reduction, which may be stature or confidence. 4.5.7 covers dynamic alignment.
Loss of control at the stance knee during a reach is a finding in its own right, independent of the distance. 3.12.7 covers dynamic valgus.
Key Learning Points
- Control through a slow movement is a different ability from power.
- The stance knee is watched, not the reaching limb.
- A reduced forward reach is a knee flexion tolerance finding.
- Backward diagonal deficits are more about the hip and trunk.
- A single direction deficit is more informative than a uniform one.
MRCS Level
How It Is Performed
In a viva this appears in the rehabilitation assessment and the expected answer distinguishes it from the hop tests.
The expected points are the prerequisite, the three directions, the light touch requirement, the measurement, the stance knee observation, the invalidation rules and the comparison by direction and by side.
Say that this test measures control rather than power, and name the contrast. 4.21.2 covers the single leg hop.
Say that you would watch the stance knee rather than the reach. 3.12.7 covers dynamic valgus.
Say that the pattern across directions carries more information than the totals. 4.1.4 covers the structured approach.
What a Positive Means
The reasoning expected is that a slow reach requires sustained eccentric control at the stance knee and hip, which is a different demand from a landing. 3.14.8 covers landing.
The forward reach loads the stance knee in flexion, which is why a knee with limited flexion tolerance loses that direction first. 3.5.4 covers the effects of flexion.
The backward diagonals demand hip extension and trunk control, which is why their deficits are often proximal. 4.4.5 covers the Trendelenburg gait.
Reach distance scales with limb length, which is why the comparison is between sides in the same patient. 4.5.8 covers limb length assessment.
How Good It Is
The test is the most reproducible in the battery, because the measurement is static at the point of reach.
Its best contribution is isolating control from power, which no other test here does. 4.21.1 covers the single leg squat.
It does not isolate a structure and is insensitive to a knee with good control and poor power.
No imaging corresponds to it. 4.1.6 covers that relationship.
No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made. Any reach threshold is a convention in the literature and this repository does not state the number.
Key Learning Points
- A slow reach demands sustained eccentric control, not landing absorption.
- The forward reach loads the stance knee in flexion.
- Backward diagonal deficits are often proximal.
- Reach distance scales with limb length, so the comparison is within patient.
- The test isolates control from power.
FRCS Level
How Good It Is
At decision level this test contributes to rehabilitation planning and contributes least to the return to sport decision.
A control deficit with normal power identifies a rehabilitation target that the hop battery would pass. 4.21.3 covers the triple hop.
A directional pattern of deficit localises the problem to the knee or to the hip, which changes the intervention. 4.4.5 covers the Trendelenburg gait.
A reduced forward reach after a cartilage or a patellofemoral procedure is a flexion tolerance finding rather than a control one. 4.20.5 covers the cartilage surgery assessment.
Normal results here do not contribute to readiness for sport, because the demands differ. 4.21.8 covers return to play decision making.
Where It Misleads
The commonest error is reading a bilateral reduction as a knee finding when it is stature, flexibility or confidence. 4.5.8 covers limb length assessment.
Weight is transferred onto the reaching foot and the attempt is counted. 4.5.7 covers dynamic alignment.
The stance knee is not watched, so a controlled failure is recorded as a good reach. 3.12.7 covers dynamic valgus.
Practice improves the result within a session, which biases the second side. 4.1.4 covers the structured approach.
A normal result is read as readiness for sport, which this test does not address. 4.21.7 covers return to sport testing.
Key Learning Points
- A bilateral reduction may be stature, flexibility or confidence.
- Transferring weight onto the reaching foot invalidates the attempt.
- Not watching the stance knee records a controlled failure as a good reach.
- Within session practice biases the second side.
- A normal result does not address readiness for sport.
Fellowship Level
Where It Misleads
At fellowship level this test is the most reproducible and the least related to the question most often being asked.
Its demands are slow and controlled while the injuries it is used around happen fast, so a normal result carries little predictive weight. 3.14.6 covers cutting manoeuvres.
Reach distance is confounded by ankle range, hip flexibility and trunk length, none of which the knee examination controls for. 4.5.8 covers limb length assessment.
The within patient comparison assumes the unaffected limb is unaffected, which after a long rehabilitation it is not. 4.3.9 covers muscle wasting.
The normative thresholds in the literature come from specific populations, and applying them outside those is an extrapolation this repository does not make. 4.21.8 covers return to play decision making.
A test's reproducibility is not its validity, and this test's strength and weakness are the same property. 4.1.6 covers that relationship.
Key Learning Points
- Slow controlled demands carry little predictive weight for fast injuries.
- Reach is confounded by ankle, hip and trunk factors.
- The unaffected limb is not unaffected after a long rehabilitation.
- Normative thresholds come from specific populations.
- Reproducibility is not validity.
Explore Further
Where this topic came from and where it goes next in the spiral.
- 4.21.1Single Leg Squat
- 4.21.6Landing Error Scoring System
- 4.21.4Crossover Hop
- 4.5.7Dynamic Alignment
- 4.4.5Trendelenburg Gait
- 4.21.8Return to Play Decision Making
References
No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 023 rather than an omission. The comparative standing of these tests is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page, and chapter 3.17 lists the studies the figures would come from. Any measurement here, including a flexion angle, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.
Safety. KneeSchool is educational and does not give individual medical advice. Seek urgent assessment for a knee that cannot bear weight after an injury, a hot swollen knee with a fever, or new numbness, weakness or coldness in the leg or foot.