Welcome to Classifications and Online Calculators in Radiology

This site was build along with the Atlas of Radiology Images to support your knowledge in radiology.

You will find here:

that are used in radiology and related fields with free access.


  • Some pages are accompanied by illustrations
  • All pages contain tags for easy navigation

The concept

The concept of this website is based on a previous site that was founded in 2008 and is still up and running. The website is composed as a book, where all sources are properly referenced, according to a good practice in scientific publications.

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    Grades of osteoarthritis by Ahlbäck

    Ahlbäck Grade Description
    Grade I Joint space narrowing (joint space < 3 mm)
    Grade II Joint space obliteration
    Grade III Minor bone attrition (0–5 mm)
    Grade IV Moderate bone attrition (5–10 mm)
    Grade V Severe bone attrition (>10 mm)


    1. Petersson I, Boegard T, Saxne T, Silman A, Svensson B. Radiographic osteoarthritis of the knee classified by the Ahlb?ck and Kellgren & Lawrence systems for the tibiofemoral joint in people aged 35-54 years with chronic knee pain. Ann Rheum Dis. 1997 Aug;56(8):493–6.
    2. Ahlbäck S. Osteoarthrosis of the knee. A radiographic investigation. Acta Radiol Diagn (Stockh). 1968;Suppl 277:7–72.

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