Table 1.

Operational definitions used in the study.

Term	Definition
Activity	Scheduled training session or match carried out with the player's own or another team.
Training session	Team training that involved physical activity under the supervision of the team coach.
Match	Friendly or competitive match against another team.
Acute knee injury	Injury to the knee joint with sudden onset and known cause, excluding contusions, leading to a player being unable to fully participate in future training or match play (i.e. time loss injury).
Sprain	Acute injury to ligament or joint capsule.
Meniscus lesion	Acute injury to the medial or lateral meniscus (verified by MRI or surgery).
Cartilage lesion	Acute injury to the articular cartilage (verified by MRI or surgery).
Bone marrow lesion	Acute injury to the bone marrow including occult fractures (verified by MRI).
Fracture	Acute injury to the bone (verified by plain X-ray).
Dislocation	Acute partial or complete dislocation of the patellofemoral joint or the knee joint.
Re-injury	Injury of the same type and to the same site as a previous injury the player had sustained in her career.
Early recurrent injury	Re-injury within two months of return to full participation after the index injury.
Late recurrent injury	Re-injury more than two months after return to full participation from the index injury.
Injury severity	Time elapsed from injury to full participation (days).
Minimal injury	Injury causing 1–3 days absence from training and match play.
Mild injury	Injury causing 4–7 days absence from training and match play.
Moderate injury	Injury causing 8–28 days absence from training and match play.
Severe injury	Injury causing >28 days absence from training and match play.
Injury mechanism
Contact injury	Injury resulting from contact with another player or object, but not the surface.
Non-contact injury	Injury not resulting from contact with another player or object.
Injury incidence	Number of injuries per 1000 player-hours.

MRI: Magnetic Resonance Imaging