This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thigh, Knee,Leg,Foot & Ankle injuries, Subject name: Orthopaedics
Insal-Salvati index is used for 
Select and explain. 
A. Olecranon, B. Patella, C. Talus, D. Scaphoid
B: Patella
Answer: B: Patella 
Explanation: a-length of patellar ligament b-length of patella INSAL-SALVATI index=a/b Normal range is 0.8 -1.2 If ratio increases it suggests patella is at a higher level-PATELLA ALTA If ratio decreases it suggests patella is at a lower level -PATELLA BAHA ref:apley's 9th edition pg no.565