Table 1 Scoring system evaluation rules and formulas

Age(years)

Age(years)

Age(years)

>16

0

≥ 25

0

Contralateral instability

≤ 16

1

< 25

2

LTI

Bilateral instability

Skeletal immaturity

No

0

No

0

Yes

1

Yes

1

Trochlear dysplasia

Dejour A-D dysplasia

None

0

None

0

Mild

1

Dejour A-D

1

Serve

2

TT-TG/PL

Patellar height(ISI)

<0.5

0

≤ 1.2

0

≥ 0.5

1

> 1.2

1

TT-TG(mm)

< 16

0

≥ 16

1

Patellar tilt (°)

≤ 20

0

> 20

1

RLPD low risk = 0–3 RLPD high risk = 4–7

RLPD low risk = 0–1 RLPD moderate risk = 2–3 RLPD high risk = 4–7

PIP = 1/1 + EXP(-PIOR). PIOR = 3.5 + Age (years)× (-0.1) + contralateral instability×0.7 + LTI× (-0.1)