Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) — free guideline decision tool
Patellar height (Insall-Salvati, Caton-Deschamps), TT-TG, TT-PCL and sulcus angle for patella alta/baja, lateralized tubercle and trochlear dysplasia. Includes how to measure and what each value means. Instant, browser-side.
Open guideline tool →Guideline-based
Implements the decision logic from published clinical guidelines.
Runs in your browser
No installation. Enter the patient's values and get a guideline recommendation instantly.
Data stays local
Nothing is uploaded. Results are for licensed clinicians only.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Patellar tendon length (IS) | 52 mm |
|---|---|
| Patellar length (IS) | 42 mm |
| Articular edge → plateau (CD) | 34 mm |
| Articular surface length (CD) | 32 mm |
| TT-TG distance | 17 mm |
| TT-PCL distance | 21 mm |
| Sulcus angle | 140 ° |
→Insall-Salvati ratio1.24
- Insall-Salvati ratio：1.24 → ≥ 1.2: patella alta (instability risk factor)
- Caton-Deschamps index：1.06 → 0.6–1.2: normal
- TT-TG distance：17 mm → 15–20 mm: borderline
Common questions
What is Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle)?
Patellar height (Insall-Salvati, Caton-Deschamps), TT-TG, TT-PCL and sulcus angle for patella alta/baja, lateralized tubercle and trochlear dysplasia. Includes how to measure and what each value means. Instant, browser-side.
How is Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) calculated? What is the core formula?
Insall-Salvati ratio < 0.8: patella baja Insall-Salvati ratio 0.8–1.2: normal Insall-Salvati ratio ≥ 1.2: patella alta (instability risk factor) Caton-Deschamps index < 0.6: patella baja Caton-Deschamps index 0.6–1.2: normal Caton-Deschamps index ≥ 1.2: patella alta TT-TG distance < 15 mm: normal TT-TG distance 15–20 mm: borderline TT-TG distance ≥ 20 mm: abnormal — threshold for tubercle medialization TT-PCL distance < 24 mm: normal TT-PCL distance ≥ 24 mm: lateralized tubercle (independent of trochlear shape) Sulcus angle ≤ 145°: normal Sulcus angle > 145°: trochlear dysplasia
When is Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) used?
Knee & lower-limb alignment imaging: lateral knee, axial CT/MRI and standing long-leg films — patellar instability and osteotomy / arthroplasty planning.
What are the key clinical points for Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle)?
Lateral radiograph at 30° flexion or sagittal MRI. Each value is graded against published reference ranges. Measurement technique and positioning change the numbers — compare like with like on follow-up. Part of the YuanDoctor MSK measurement topic.
What are the limits and cautions when using Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle)?
For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
Does Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) upload patient data? Where is it calculated?
Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
How is Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) calculated in practice? Can you show a worked example?
Inputs: Patellar tendon length (IS) 52 mm, Patellar length (IS) 42 mm, Articular edge → plateau (CD) 34 mm, Articular surface length (CD) 32 mm, TT-TG distance 17 mm, TT-PCL distance 21 mm, Sulcus angle 140 ° → Result: Insall-Salvati ratio 1.24（Insall-Salvati ratio: 1.24 → ≥ 1.2: patella alta (instability risk factor), Caton-Deschamps index: 1.06 → 0.6–1.2: normal, TT-TG distance: 17 mm → 15–20 mm: borderline）
Run Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle) now
Patellar height (Insall-Salvati, Caton-Deschamps), TT-TG, TT-PCL and sulcus angle for patella alta/baja, lateralized tubercle and trochlear dysplasia. Includes how to measure and what each value means. Instant, browser-side.
Open guideline tool →For licensed clinicians. Not a substitute for clinical judgement.
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