Table 1

Participants' characteristics at the start of follow-up and number of pairs affected by anterior cruciate ligament rupture during follow-up

AllMenWomen
No ACL ruptureACL ruptureNo ACL ruptureACL rupture
Twin, individual level (n)*88 41440 55367346 466722
Age at start of follow-up (years) (median (IQR))32 (17–47)32 (17–46)17 (17–31)33 (17–48)17 (17–31)
Primary school†
(≤9 years) (n (%))
26 612 (30.1)12 652 (31.2)117 (17.4)13 756 (29.6)87 (12.1)
Upper secondary school†
(1–4 years) (n (%))
36 335 (41.1)17 188 (42.4)325 (48.3)18 520 (39.9)302 (41.8)
College/university†
(>1 years) (n (%))
25 467 (28.8)10 713 (26.4)231 (34.3)14 190 (30.5)333 (46.1)
Body mass index (kg/m2) (mean (SD))23.3 (3.5)23.9 (3.3)24.2 (3.4)22.7 (3.7)22.9 (3.41)
Twin, pair level (N)‡44 207
Monozygotic pairs (N)14 53162042147863250
Dizygotic pairs, same sex (N)17 40978302329099248
Dizygotic pairs, opposite sex§ (N)12 26711 86640111 866401
  • *Lower case 'n' represents individuals.

  • †Highest level of education reached at the start of follow-up.

  • ‡Upper case 'N' represents pairs. Pair level N for anterior cruciate ligament rupture includes pairs in which at least one twin in the pair was affected.

  • §Pairs consisting of male and female twins—that is, the same N values are presented for men and women.

  • ACL, anterior cruciate ligament.