Arthrogenic Muscle Inhibition of the Knee: A Surgeon-Focused Narrative Review of Diagnosis and Management.

Arthrogenic muscle inhibition (AMI) is a reflexive suppression of quadriceps motor drive that arises from abnormal joint afferent signaling rather than structural failure. It is a common and underrecognized barrier to recovery after knee injury and surgery, reported in more than half of acute anterior cruciate ligament (ACL) injuries and in roughly one-third of patients early after total knee arthroplasty. Even when a reconstruction, repair, or arthroplasty is technically successful, persistent inhibition can limit voluntary quadriceps activation, terminal knee extension, gait, and functional strength. This narrative review synthesizes the current evidence with a surgeon-facing perspective, organized around three areas: the neurophysiology of AMI, its clinical assessment and diagnosis, and current management strategies. The pathophysiology is time-dependent: acute AMI is predominantly a spinal reflex phenomenon driven by effusion, pain, inflammation, and altered mechanoreceptor input, whereas chronic AMI reflects corticospinal and cortical reorganization that responds less reliably to joint-directed treatment alone. AMI has no diagnostic gold standard and is recognized clinically after structural causes are excluded, with the Sonnery-Cottet (SANTI) classification providing a practical bedside grade and quantitative measures such as the central activation ratio reserved for research settings. Among management options, neuromuscular electrical stimulation carries the strongest evidence, supported by meta-analyses of randomized trials after ACL reconstruction, with earlier initiation associated with greater quadriceps strength recovery. Targeted activation exercises and cryotherapy are widely used and supported by observational and experimental work, though the evidence behind them is less direct. We consolidate this evidence into graded summary tables and a proposed bedside clinical pathway. Early recognition of AMI, particularly in high-risk perioperative windows, allows the surgeon to distinguish neuromuscular inhibition from mechanical block, guide patient-specific counseling, and coordinate treatment before recovery is compromised.