Solomonow et al. used surface EMG in normal subjects and ACL-deficient patients on a Cybex dynamometer, plus a direct ACL-loading cat model. The study asked whether a reflex arc exists between ACL mechanoreceptors and thigh musculature, and whether that arc persists or can be substituted when the ACL is torn.
Before this paper, hamstring strengthening after ACL injury was recommended by some clinicians but lacked experimental proof — no one had directly demonstrated a neurophysiologic link between the ligament and the muscles.
This study established that link. When you see an ACL-deficient patient, recognize that hamstring strength is not a rehabilitation adjunct. It is the primary substitute stabilizing mechanism, operating through a reflex arc that directly replaces ligament function.
For your non-operative candidates: the reflex compensation works well at slow controlled loads (daily activity) but breaks down at the high forces and rapid loading rates of contact sport. This is why well-conditioned recreational athletes can cope without reconstruction while high-demand athletes typically cannot.
Practically, hamstring strengthening can and should begin immediately after ACL injury or repair. This paper confirmed it places no stress on the damaged ligament, making early hamstring work both safe and mechanistically essential.
Solomonow et al. used surface EMG in normal subjects and ACL-deficient patients on a Cybex dynamometer, plus a direct ACL-loading cat model. The study asked whether a reflex arc exists between ACL mechanoreceptors and thigh musculature, and whether that arc persists or can be substituted when the ACL is torn.
Before this paper, hamstring strengthening after ACL injury was recommended by some clinicians but lacked experimental proof — no one had directly demonstrated a neurophysiologic link between the ligament and the muscles.
This study established that link. When you see an ACL-deficient patient, recognize that hamstring strength is not a rehabilitation adjunct. It is the primary substitute stabilizing mechanism, operating through a reflex arc that directly replaces ligament function.
For your non-operative candidates: the reflex compensation works well at slow controlled loads (daily activity) but breaks down at the high forces and rapid loading rates of contact sport. This is why well-conditioned recreational athletes can cope without reconstruction while high-demand athletes typically cannot.
Practically, hamstring strengthening can and should begin immediately after ACL injury or repair. This paper confirmed it places no stress on the damaged ligament, making early hamstring work both safe and mechanistically essential.