The site had difficulties to recruit. Some associated investigators can not be involved in the study anymore and others centers contacted don't have enough ressources to conduct the study. Premature end of inclusions on 07/10/2025 & LPLV on11/27/2025

Monocentric, prospective, randomised, double-blind study of two parallel groups of 66 patients with post-reconstruction ACL hamstring contracture treated with an ultrasound-guided injection at two points on the body of the hamstring

• Group 1: botulinum toxin: 100 units (0.5ml) in 1 injection
• Group 2: placebo: 0.5 ml in 1 injection

The study includes three assessments: one month after ligamentoplasty (inclusion visit) and then at M2 and M5. The therapeutic benefit of the study treatments is based on the evolution of the extension defect at M2.

Inclusion Criteria:

• Patient over 18 years of age
• Patient who has read and signed the consent form for participation in the study
• Patient operated on for primary ACL ligamentoplasty with or without meniscal repair
• Patient with reducible flatus >10° at 1 month post ligamentoplasty

Exclusion Criteria:

• Revision ligamentoplasty
• Multi-ligament knee
• Patient under court protection, guardianship or trusteeship
• Patient not affiliated to the French social security system
• Patient participating in another therapeutic protocol
• Pregnant woman or woman of childbearing age without effective contraception
• Patient unable to understand the informed information and/or to give written informed consent: dementia, psychosis, disturbed consciousness, non-French speaking patient
• Patient with known hypersensitivity to botulinum toxin
• Patient with peripheral neuromuscular dysfunction or pronounced atrophy of the semitendinosus muscle
• Patient treated with anticoagulants, chloroquine (or hydroxychloroquine)
• Patient treated in the previous seven days with antibiotics or muscle relaxants (such as tubocurarine)

A placebo is used