🦿 Patellofemoral Measurements (Insall-Salvati / Caton-Deschamps / TT-TG / Sulcus Angle)
UseKnee & lower-limb alignment imaging: lateral knee, axial CT/MRI and standing long-leg films — patellar instab…
SourceInsall J, Salvati E. Patella position in the normal knee joint. Radiology 1971;101:101-104
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
Lateral radiograph at 30° flexion or sagittal MRI.
When to use
Knee & lower-limb alignment imaging: lateral knee, axial CT/MRI and standing long-leg films — patellar instability and osteotomy / arthroplasty planning.
How it works
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
Key points
- 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.
References
- Insall J, Salvati E. Patella position in the normal knee joint. Radiology 1971;101:101-104
- Caton J, et al. Patella infera. Rev Chir Orthop 1982;68:317-325
- Dejour H, et al. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994;2:19-26
- Seitlinger G, et al. Tibial tubercle-posterior cruciate ligament distance. Am J Sports Med 2012;40:1119-1125
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
Verification & sources · governance
FAQ
Frequently asked questions
- 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）