Table 1 Inclusion and exclusion criteria

Eligible participants will have had:

• Previous major knee injury or knee surgery

• A complete ACL tear as visualized on MRI

• Associated posterior cruciate ligament (PCL) or medical collateral ligament (MCL) injury grade III

° The ACL injury can be either “isolated” or combined with one or several of the following injuries visualized on MRI and/or arthroscopy:

• Concomitant severe injury to contra-lateral knee

▪ A meniscus tear that is either left untreated or treated with a partial resection

• Injury to the lateral/posterolateral ligament complex with significantly increased laxity

▪ A small, stable meniscus tear treated with fixation, but with the fixation not interfering with the rehabilitation protocol

• Unstable longitudinal meniscus tear that requires repair and where the following postoperative treatment (e.g. bracing and limited range of motion) interferes with the rehabilitation protocol

▪ Cartilage changes verified on MRI with an arthroscopically determined intact surface.

• Bi-compartmental extensive meniscus resections

• A radiographic examination with normal joint status or combined with either one of the following findings:

• Cartilage injury representing a full thickness loss down to bone

° A small-avulsed fragment located laterally, usually described as a Segond fracture, JSN grade 1 or osteophytes grade 1 as determined by the OARSI atlas[15]

• Total rupture of MCL/LCL as visualized on MRI.

• History of deep vein thrombosis (DVT) or a disorder of the coagulative system

• Claustrophobia

• Prior or current use of anabolic steroids

• General systemic disease affecting physical function

• Chromosomal disorders

• Medications that interfere with testosterone production or function, including but not limited to 5α-reductase inhibitors

• Any other condition or treatment interfering with the completion of the trial