Manual therapies, targeting the knee and lumbopelvic region, have shown the ability to improve neuromuscular quadriceps function in individuals with knee pathology. It is still unknown if manual therapies may alter impaired spinal reflex excitability, thus identifying a potential mechanism in which manual therapy may improve neuromuscular function following knee injury. The goal of this study was to determine the effect of local and distant mobilisation/manipulation interventions on quadriceps spinal reflex excitability. Seventy-five people with a history of knee joint injury and current quadriceps inhibition volunteered for this study. Participants were randomised to one of five intervention groups: lumbopelvic manipulation (grade V), lumbopelvic manipulation positioning (no thrust), grade IV patellar mobilisation, grade I patellar mobilisation, and control (no treatment). Changes in spinal reflex excitability were quantified by assessing the Hoffmann reflex (H-reflex), presynaptic, and postsynaptic excitability. A hierarchical linear-mixed model for repeated measures was performed to compare changes in outcome variables between groups over time (pre, post 0, 30, 60, 90 min). There were no significant differences in H-reflex, presynaptic, or postsynaptic excitability between groups across time.
The study found that manual therapies directed to the knee or lumbopelvic region didn’t acutely change quadriceps spinal reflex excitability. While manual therapies might improve impairments and functional outcomes the underlying mechanism does not seem to be related to changes in spinal reflex excitability.