Understanding the Insall-Salvati Ratio Assessment
A radiologic measurement used to assess for **Patella Alta** (high-riding patella) or **Patella Baja** (low-riding patella).
Watch How It's Done
How do I start?
N/A (Radiographic measurement).
What happens?
Measured on a lateral knee radiograph at 30° of knee flexion. The ratio is calculated by dividing the length of the **Patellar Tendon (LT)** by the greatest diagonal length of the **Patella (LP)**.
In Plain English
What Does a Positive Result Mean?
A **normal ratio is 1.0 (with a variation of $\pm 0.2$)**. A ratio **> 1.2** indicates **Patella Alta**. A ratio **< 0.8** indicates **Patella Baja**.
Helpful Tip:
Patella Alta is a risk factor for Patellofemoral Instability (dislocation).
Safety First
This guide is to help you understand what happens in a clinic. Do not try to diagnose yourself. If you have severe pain, swelling, or cannot put weight on your leg, please visit an urgent care center or your doctor immediately.
Other Knee Tests
Pivot Shift Test
To dynamically assess for **anterolateral rotatory instability** of the knee, which is highly indicative of a **complete ACL tear**.
Posterior Drawer Test of the Knee
To assess the integrity of the **Posterior Cruciate Ligament (PCL)**.
Posterior Sag Sign (Gravity Drawer Test)
To detect a rupture of the **Posterior Cruciate Ligament (PCL)** by observing the effect of gravity.
Slocum Test (Anterolateral Rotatory Instability)
To assess for **anterolateral rotatory instability** and the function of the **Anterolateral Ligament** (a dynamic variant of the Anterior Drawer).