The Clinical SANTI classification of arthrogenic muscle inhibition is a reliable and reproducible tool after ACL rupture.
When it comes to anterior cruciate ligament (ACL) injuries, timely diagnosis and targeted rehabilitation are essential for optimal recovery. One of the common complications, arthrogenic muscle inhibition (AMI), can severely delay healing if not managed properly.
This article summarises key findings from the study “Clinical SANTI classification of arthrogenic muscle inhibition has an excellent inter-rater and intra-rater reliability in preoperative and post-operative anterior cruciate ligament rupture” (Le Guen et al., 2025).
To explore further, you can read more of Professor Étienne Cavaignac’s published studies available on his website.
Arthrogenic muscle inhibition is a reflex impairment of the quadriceps, particularly the vastus medialis oblique (VMO), following knee trauma or surgery. This neuromuscular dysfunction originates in the central nervous system and is often associated with a contracture of the hamstrings. In the context of ACL injuries, failing to detect and treat AMI early can result in significant sequelae such as gait abnormalities, quadriceps atrophy, joint stiffness, persistent pain or even early osteoarthritis.
Anterior cruciate ligament ruptures are common in athletes and active individuals. The ACL plays a critical role in stabilising the knee joint. When ruptured, it frequently leads to instability, functional limitations and a higher risk of further damage to the knee’s cartilage and menisci if left untreated.
The SANTI classification, introduced in 2022, provides a clinical framework for identifying AMI in patients before and after ACL surgery. It enables targeted interventions such as specific rehabilitation strategies or surgical planning to address quadriceps inhibition effectively.
The study conducted at CHU Toulouse involved 140 patients with acute ACL ruptures. AMI was assessed during preoperative consultations and again three weeks post-surgery. Four professionals from different disciplines (orthopaedic surgeons, a sports physician and a physiotherapist) evaluated the patients independently.
The results demonstrated excellent inter-rater reliability of the AMI classification:
In terms of intra-rater reliability, repeated evaluations by the same physiotherapist also yielded strong agreement:
These findings support the classification’s robustness and suitability for widespread clinical use. They also validate it as a shared diagnostic language among all professionals involved in ACL rehabilitation.
Early recognition and classification of AMI can guide tailored interventions depending on the AMI grade. Grades 1A and 2A, for example, are often reversible through simple in-office exercises that focus on:
For Grade 2A, attention must also be given to relieving hamstring contracture through repeated resisted contractions followed by relaxation. Once the hamstrings are fatigued and passive extension is restored, VMO reactivation exercises follow.
Higher grades (1B or 2B) often require structured neuromotor rehabilitation and biofeedback-based therapy over multiple sessions. These techniques enhance central and peripheral neuromuscular control, targeting the root causes of AMI.
The high reproducibility of the classification means it can become a routine tool for physiotherapists and surgeons. In practice, it enables:
Interestingly, the study found no significant correlation between preoperative AMI and its persistence postoperatively, suggesting that timely intervention, even pre-surgery, can mitigate long-term consequences. Patients who had AMI preoperatively benefited from targeted prehabilitation sessions, resulting in a much lower incidence of AMI postoperatively (only 16% versus 49% pre-op).
This evidence aligns with Professor Cavaignac’s broader approach to ACL treatment, which combines surgical precision with personalised rehabilitation protocols.
The SANTI classification is a robust and practical clinical tool that improves the diagnosis and management of arthrogenic muscle inhibition in patients undergoing ACL surgery. Its proven inter- and intra-rater reliability ensures consistency across healthcare professionals, improving outcomes through early detection and personalised rehabilitation strategies.
To explore further research by Professor Cavaignac and his team, browse the latest studies available on his official website. If you are dealing with a knee injury or preparing for ACL surgery, Professor Cavaignac is highly recommended for his expertise, surgical excellence, and commitment to patient recovery.
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