Introduction The Achilles tendon Total Rupture Score (ATRS) is the most commonly used patient reported outcome in patients with an acute Achilles tendon rupture. The score contains ten items of which the last three concerns tasks that some patients cannot and some do not perform. No manual for the use of ATRS has been developed. The purpose was to investigate how ATRS responds at 4, 6 and 12 months after rupture and develop a manual for the use of ATRS.

Materials and methods This study was performed as a retrospective registry study analysing prospectively gathered data from the Danish Achilles tendon Database. The data was gathered 4, 6 and 12 months after rupture. The original score based on 10 items was compared with a score based on the first 7 items adjusted to the same scale as the original score. Density- and scatterplots were made and differences between the scores were tested by t-test or Mann–Whitney U test.

Results 2790 completed ATRS scores were included. The 7-item score statistically significantly overestimated the value of the 10 items score at all time points (p<0.001) but only at 4 months the difference was clinical relevant (9.7points).

Conclusion The ATRS cannot be recommended for use at 4 months past rupture, as the last 3 items skew the score. If the ATRS is used before 6 months the last three items could be omitted. A manual for the use of the ATRS will be developed defining how and when the score should be applied.