The Knee Prone Heel-to-Butt Test assesses how close the heel can move toward the buttock in prone. It can help track knee flexion range, anterior thigh mobility context, pelvic compensation and side-to-side differences.
A client may struggle to kneel, perform deep knee flexion tasks, tolerate quadriceps stretching or bend the knee fully in prone. The Knee Prone Heel-to-Butt Test provides a practical way to assess this position and record whether range, symptoms or compensation changes over time.
The MAT article describes the test in prone and states that at least 120 degrees is typically considered normal, while noting that ROM varies across individuals. (matassessment.com)
Test name: Knee Prone Heel-to-Butt Test
Purpose: Assess prone knee flexion / heel-to-butt range
What it assesses: Knee flexion range, anterior thigh mobility context and pelvic control
Equipment: Measurz inclinometer or equivalent inclinometer
Key finding: Knee flexion angle or heel-to-butt distance, depending on protocol
Best used with: Knee flexion, knee extension, modified Thomas test, hip extension and squat/kneeling assessment
Key limitation: Hip position, pelvic movement and symptoms can affect the result
The Knee Prone Heel-to-Butt Test assesses the client’s ability to bend the knee while lying prone and bring the heel toward the buttock. It may be recorded as an angle or, in some settings, as heel-to-butt distance.
It is used to track prone knee flexion, compare sides, monitor progress and add context to anterior thigh mobility, kneeling, squatting and sport tasks.
It measures prone knee flexion range or heel-to-butt position. It does not isolate rectus femoris length, identify the source of symptoms or measure lower-limb function on its own.
The test may be active, where the client bends the knee, or passive, where the movement professional guides the heel toward the buttock. Record the method because active and passive results provide different information.
Athletes, gym clients, runners, field sport athletes, clients returning to kneeling or squatting, and clients where knee flexion or anterior thigh mobility tracking is useful.
Measurz inclinometer or equivalent inclinometer
Treatment table or mat
Optional tape measure if recording heel-to-butt distance
Measurz app for baseline and follow-up recording
Ask the client to lie prone with both knees extended. The movement professional stands beside the test leg and monitors the pelvis.
Ask the client to bend the knee and bring the heel toward the buttock. Monitor whether the pelvis lifts or the hip moves. Place the inclinometer consistently on the lower leg according to the chosen protocol and record the angle. If using a distance score, measure heel-to-butt distance with the same landmark each time.
Ask about pain, stretch, tightness or cramping. Stop if pelvic movement changes the test, symptoms meaningfully alter the movement, or the client cannot maintain position.
Record either knee flexion angle in degrees or heel-to-butt distance. Use the same scoring method for retesting.
The MAT article states that at least 120 degrees is typically considered normal, but this should be treated as a practical reference rather than a universal rule. (matassessment.com)
Evidence level: Level 2, related or closest available reference values.
The MAT article provides at least 120 degrees as a practical reference. Interpret this with the client’s baseline, opposite side, symptoms, pelvic movement and activity demands. (matassessment.com)
A 2020 reliability study of the Ely and Active Knee Extension tests reported excellent reliability for the Ely test and an MDC95 of 8 degrees in the studied asymptomatic young adult sample. This supports the importance of using consistent pelvic control and measurement procedures when interpreting change in prone knee flexion-style testing.
Common errors include allowing pelvic lift, forcing the heel toward the buttock, inconsistent device placement, changing scoring method, ignoring symptoms and interpreting the result as isolated anterior thigh length.
Use the test for baseline knee flexion, side-to-side comparison, progress tracking, kneeling context, squat context and monitoring symptom response during knee bending positions.
Record baseline score, side tested, knee flexion angle or heel-to-butt distance, active or passive ROM, pain score, symptom location, pelvic compensation, test position, device used, comparison with the other side, related strength findings, related functional findings and retest date.
Knee Flexion Test
Knee Extension Test
Hip Modified Thomas Test
Hip Extension Test
Squat Assessment
Kneeling tolerance notes
It measures how close the heel can move toward the buttock while the client lies prone.
The MAT article states that at least 120 degrees is typically considered normal, but this varies by client and protocol. (matassessment.com)
Yes. Pelvic lift changes the meaning of the test and should be noted in Measurz.
It is related, but the heel-to-butt version can provide additional information about prone knee bending and pelvic compensation.
The test assesses prone knee flexion / heel-to-butt range.
Record angle or distance consistently.
Monitor pelvic compensation.
Label active and passive ROM separately.
Track symptoms and progress in Measurz.
Olivencia, O., Godinez, G. M., Dages, J., Duda, C., Kaplan, K., & Kolber, M. J. (2020). The reliability and minimal detectable change of the Ely and Active Knee Extension tests. International Journal of Sports Physical Therapy, 15(5), 776–782. https://doi.org/10.26603/ijspt20200776
Fraeulin, L., Holzgreve, F., Brinkbäumer, M., Dziuba, A., Friebe, D., Klemz, S., et al. (2020). Intra- and inter-rater reliability of joint range of motion tests using tape measure, digital inclinometer and inertial motion capturing. PLOS ONE, 15(12), e0243646. https://doi.org/10.1371/journal.pone.0243646
