4DEYE tracking a shoulder joint in real time and reading out the angle

AI musculoskeletal assessment · digital rehab

An X-ray sees the body at rest.4DEYE sees it in motion.

One simple arm raise. In five minutes, numbers show where the joint goes off track and which muscles compensate.

Talk to us Approvals and evidence

MFDS Class II medical device
2024 · billable
Running at 26 sites
Incl. Korea's largest spine & joint hospital
6 SCI papers
5 validity · 1 treatment effect
GMP · ISO 13485
Quality system audited
Payback in 3 weeks to 3 months
From real assessment volumes

The gap

Musculoskeletal pain care has a gap in functional diagnosis and rehab.

No preventive screening
No check-up catches musculoskeletal problems before pain starts.
Imaging only shows structure
X-ray and MRI show damage, not the real cause: joint dysfunction.
Short-term symptom relief
Symptoms ease for a while, but the functional cause remains, so pain returns.
Care stops outside the hospital
Discharged patients struggle alone. Old habits return and progress is lost.

Disc abnormalities with no pain: 87.6%; Spine 2015
When the injection wears off: 6 weeks; KSSTA 2024
Chronic knee pain becoming arthritis: 31%; AJSM 2017
Home exercise dropout: 50%; JMIR 2018

From one simple motion, 4DEYE measures four things.

Range of motion (ROM)
Does the joint move enough?
e.g. A stiff ankle breaks down posture.
Ref) Bennell 1998 · Konor 2012
Alignment
Is the joint straight on its axis?
e.g. Knee collapsing inward: ACL injury risk ↑
Ref) Hewett 2005
Asymmetry
Are left and right in balance?
e.g. Favouring one side builds up load
Ref) Plisky 2006
Compensation
Is another region doing the work instead?
e.g. Weak glutes make the lower back take over
Ref) Sahrmann 2002

Real screens

One assessment is just the start

The assessment finds compensation and joint dysfunction, and targeted rehab is prescribed. Home results set the baseline for the next assessment. A loop, not just a device.

4DEYEDxAssessment · hospital

AI screening
AI analysis & prescription
Report

4DEYEDTxRehab · home

Mobile rehab
Live monitoring

Results feed the prescription

Rehab data sets the next baseline

4DEYE overview video — Overview: what 4DEYE does.

A 4DEYE report showing left and right range of motion, muscle balance and risk — The report: left/right range of motion, compensation, and tight or weak muscles on one screen.

Three ways to assess joints body-wide

Single-joint motion analysis
The core test: one simple motion shows if a joint leaves its path.
Every joint, shoulder to ankle
Multi-joint motion analysis
Shows, joint by joint, where the body breaks down in movements like an overhead squat.
Athletes · groups
Static posture
Checks standing alignment in 3D, in a three-second capture.
Screening · pre-checks · three seconds

Hand function

Detailed analysis of fingers, wrist and elbow. Needs a dedicated attachment; separate subscription.

Physician orders, physical therapist runs. Five minutes per assessment, half a day of training. A one-page PDF links to PACS and insurance claims.

Rehab usually ends at discharge

No one knows what exercise was done, and the next visit brings only “a bit better.” 4DEYE DTx fills that gap with data. Unlike exercise apps, its effect was shown in a confirmatory trial.

The prescription travels
Pick exercises to match the results, set sets, reps and frequency, and the plan goes to the patient’s phone. No paper handouts.
A camera scores the motion
At home, the camera scores posture accuracy and corrects errors on the spot.
You see who slipped
Adherence and pain (NRS) trends on one screen. AI flags drop-offs; send a reminder by KakaoTalk or text.

Accuracy first, then effect — proven in order

Five papers show accurate, repeatable measurement against VICON, from single joints to whole-body movement. The sixth shows exercise content built on it corrects posture.

Same motion, VICON vs. 4DEYE: how close are the values?

ICC near 1.00 means values match VICON. ≥ 0.75 is "good"; ≥ 0.90 is "excellent".

0
Poor0.5
Moderate0.75
Good0.9
Excellent

Concurrent validity

ICC 0.75–0.99

Hip, knee and trunk measured together · Applied Sciences 2024

Angle-trajectory validity

ICC 0.86–1.00

Sitting, standing and squats · Journal of Human Kinetics 2023

Test–retest reliability

ICC 0.68–0.99

Same motion, same value on retest · Sensors 2023 · JHK 2023

ICC near 1.00 means close agreement with VICON — not that a treatment works. We keep the two claims separate.

How each one measures

VICON

Reflective markers on every joint
Infrared cameras in a dedicated lab
20–30 min setup

4DEYE

Nothing attached to the body
Five RGB cameras, existing rehab room
5-minute test

Beyond measurement — effect, too

In a cluster RCT of 36 adolescents (Medicine, IF 1.4), digital exercise content alone improved posture about as much as in-person therapist coaching.

Knee pain confirmatory trial, on our product

Prof. Lee Byung-hoon’s team, Orthopaedic Surgery, Gachon University Gil Medical Center · Single-centre · assessor-blinded · parallel-group · ITT · n=151 (78 vs 73) · 12 weeks

Prescribed rehab exercise in front of a mounted tablet — Participants exercise in front of a mounted tablet; the camera corrects their form in real time.

Primary endpoint · KOOS-12 function score

+5.24P < .001

Secondary outcomes improved too

Quality of life (SF-12 physical) +7.35 · mental +5.83
Knee flexion ROM +3.08°
Adherence 81.4% (control 77.2%)

IRB GCIRB2025-212 · CRIS KCT0011905

Six SCI(E) papers, in Sensors, Applied Sciences, Journal of Human Kinetics, Medicine and more.

All papers and trials

Real payback periods

Payback in three weeks to three months

Not projections: based on actual assessment volumes. Hospital names are initials per contract.

Bundang Hospital B passes 1,500 assessments a month

At a single hospital, in one month.

Bundang Hospital B
Ansan Hospital O
Seoul Hospital C

Cumulative monthly payback. Volumes vary by hospital, so payback periods vary too.

Bundang Hospital B
266% in three weeks
266% of the purchase price recovered in three weeks, from 1,278 assessments. Monthly volume passed 1,500 as of Sep 2026.
Payback
266%
Time to payback
3 weeks
Ansan Hospital O
193% in two months
Payback rose from 62% to 193% in two months; monthly volume from 182 to 422 (Sep 2026).
Payback
193%
Time to payback
2 months
Seoul Hospital C
100% in three months
Full purchase price recovered in three months. Monthly volume reached 312 as of Sep 2026.
Payback
100%
Time to payback
3 months

No upfront cost. Profit from the first patient.

Upfront cost: KRW 0. Subscription, no equipment to buy
Billing: Per assessment; rate drops as volume grows
Term: 36 months, monthly minimum
Break-even: No upfront spend. Profit from the first patient

Rates and monthly minimums depend on hospital size and joints in use. We cover them in a consultation.

Why 4DEYE

Why choose 4DEYE?

Assessment devices stop at evaluation. Rehab apps prescribe without assessing. Only both turn one assessment into a cycle of care.

Assessment devices only
Posture and basic range of motion
- Measure
- →
- Prescribe
- →
- Re-measure
The loop breaks
Stops at assessment. With no link to treatment, the data is used once and lost.
4DEYE
Measure, prescribe, re-measure
- Measure
- →
- Prescribe
- →
- Re-measure
The loop closes
Each prescription comes from that person’s measured compensation, and results feed the next measurement.
Rehab app only
Same protocol exercises for everyone
- Measure
- →
- Prescribe
- →
- Re-measure
The loop breaks
Prescribes without assessing what to fix. Progress relies on self-report.

Categories based on public company materials, as of 2026. Specifications may change.

Who it is for

Care in hospitals. Prevention in sports, schools, industry and care facilities.

Features by use

Clinical motion analysis is different, feature by feature

The wellness edition for sports, schools, industry and senior care involves no medical judgement: it offers posture and posture type data, growth prediction, a personalized exercise app, and injury-risk screening in sports. Joint-by-joint motion analysis, clinical use and claims, and digital therapeutic prescription are clinical edition only.

Feature	Clinical edition 4DEYE Dx (MFDS-approved medical device) / DTx Clinics and hospitals · rehab medicine · orthopedics · physiotherapy	Wellness edition For sports, schools, industry and seniors · non-medical Athletes · students · workers · older adults
Motion analysis · clinical use
Single- and multi-joint motion analysis Range of motion · compensation · left–right asymmetry	Included	Not included
Movement screening Injury-risk screens such as Y-balance and overhead squat · sports only	Included	Included
Tight and weak muscles · risk grade Findings that support clinical judgement	Included	Not included
Hand function test Detailed finger, wrist and elbow analysis · separate attachment	Separate subscription	Not included
Report linked to PACS and claims Connected to medical records and billing	Included	Not included
Treatment · follow-through
Digital therapeutic prescription Clinician-prescribed · camera scoring · confirmatory trial evidence	Included	Not included
Personalized exercise app Exercise matched to results · adherence tracking	Included	Included
Posture
Current posture measurement 3 seconds · coronal, sagittal and transverse alignment	Included	Included
Posture type classification Forward head · rounded shoulders · pelvic tilt and more	Included	Included
Measurement data · trends Individual and group records on one yardstick	Included	Included
Growth · vital signs
Growth prediction model Growth trends for students · in use in schools	Included	Included
Heart rate · respiratory rate Contactless, via remote photoplethysmography (rPPG) from camera video	Coming soon	Coming soon
Heart rate variability (HRV) · stress index Based on LF/HF and SDNN	Coming soon	Coming soon
Blood pressure · oxygen saturation Collected during the same session	Coming soon	Coming soon

Clinical edition

4DEYE Dx (MFDS-approved medical device) / DTx

Wellness edition

For sports, schools, industry and seniors · non-medical

Motion analysis · clinical use

Single- and multi-joint motion analysis
Range of motion · compensation · left–right asymmetry
IncludedNot included
Movement screening
Injury-risk screens such as Y-balance and overhead squat · sports only
IncludedIncluded
Tight and weak muscles · risk grade
Findings that support clinical judgement
IncludedNot included
Hand function test
Detailed finger, wrist and elbow analysis · separate attachment
Separate subscriptionNot included
Report linked to PACS and claims
Connected to medical records and billing
IncludedNot included

Treatment · follow-through

Digital therapeutic prescription
Clinician-prescribed · camera scoring · confirmatory trial evidence
IncludedNot included
Personalized exercise app
Exercise matched to results · adherence tracking
IncludedIncluded

Posture

Current posture measurement
3 seconds · coronal, sagittal and transverse alignment
IncludedIncluded
Posture type classification
Forward head · rounded shoulders · pelvic tilt and more
IncludedIncluded
Measurement data · trends
Individual and group records on one yardstick
IncludedIncluded

Growth · vital signs

Growth prediction model
Growth trends for students · in use in schools
IncludedIncluded
Heart rate · respiratory rate
Contactless, via remote photoplethysmography (rPPG) from camera video
Coming soonComing soon
Heart rate variability (HRV) · stress index
Based on LF/HF and SDNN
Coming soonComing soon
Blood pressure · oxygen saturation
Collected during the same session
Coming soonComing soon

Contactless vital signs are developed and launching soon; the wellness edition shows them as reference indicators without medical judgement. Hand function testing needs a separate attachment and subscription.

Users and partners

Already in use and working with us

Clinical and research

Hospitals and clinics

Professional sport

Public and education

Overseas partners

Australia
Canada
Singapore

Clinical and public partners

Research in hospitals, results in the field

University hospital teams and an open lab validate performance and safety; a public education programme tests it in the field.

Prof. Lee Sang-heon’s team, Rehabilitation Medicine, Korea University Anam Hospital
Clinical site 1 · PI, non-specific low back pain DTx trial under way
Photo: Korea University Medicine PR Manager, CC BY-SA 4.0, Wikimedia Commons
Prof. Lee Byung-hoon’s team, Orthopaedic Surgery, Gachon University Gil Medical Center
Clinical site 2 · PI, chronic knee pain DTx trial completed
Photo: Narubaru7, CC BY 4.0, Wikimedia Commons
Open Lab, Korea University Guro Hospital
Research lab · R&D and clinical advice
Photo: Korea University Medicine PR Manager, CC BY-SA 4.0, Wikimedia Commons
Gyeonggi Provincial Office of Education
2024–present · student postural imbalance programme
Photo: SYM Healthcare · student postural imbalance prevention class

Organizations we’ve worked with

Start putting numbers on movement

Clinics, sports, schools, workplaces or senior care: see a live demo and the operating terms.

Talk to us Get the brochure