Introduction Phenotypisation of the lumbar disks degenerative lesions was the topic of last 4 meetings of the ISSLS focus group on disc degeneration. In 2014 the focus was enlarged to the whole lumbar spine degeneration. No consensus exists for denitions of dierent degenerative diseases nor for classication of these diseases. The existing scoring systems are usually limited to a single structure e.g. disc, facets, spinal canal, etc Purpose The aim of this study is to present a simple method to describe the normal and global radiological changes of the lumbar spine and by that to get a tool for classication. Method Our tool is derived from the TNM classication system used for tumors. It includes 10 main categories and for each one up to 4 levels of modiers. The findings were encoded in a standardized manner summarized in table. Results In a rst trial 200 MR examinations of consecutive patients of dierent age and gender referred to MRI for lumbar spine examination were encoded. The mean time for coding was 3 minutes. Examples of correlations were done with respect to age and gender. There was strong correlation of disc degeneration with age not with gender. There was no dierence in the frequency of protrusion and extrusion in the categories of age and gender. The number of phenotypes done by algorithm is depending on the number of characteristics introduced in the system. Conclusion The presented proposal for phenotypisation of changes of the lumbar spine seems to be a valuable tool to describe these changes and allow to form groups of phenotypes. It can be the base to compare groups and subgroups and to allow correlations within the groups and subgroups. The system can easily be extended with additional characteristics. It allows better comparison of dierent studies of the lumbar spine 
Bold gures means the code for categories and modiers. In the same way other main categories like Disc Height, End plate Changes, Neuroforaminal Stenosis, Deformities are to be encoded. Example for encoding: male patient in 3rd decennium spinal narrowing by herniation with extrusion in L5/S1 in central position. A,3;G,M; I ,H,E, V,C |