Recovering from a knee injury or surgery, like an anterior cruciate ligament reconstruction (ACLR), is a challenging journey. Strength, function, and confidence often seem just out of reach. But what if the problem isn’t just in the muscles themselves, but in the way your nervous system communicates with them? That’s the case with arthrogenic muscle inhibition (AMI)—a condition where your body’s natural responses after injury disrupt muscle activation and strength.

Three years ago today, Grant Norte, Justin Rush, and I published a review paper in the Journal of Sports Rehabilitation. We explored the available evidence for adjunct therapies to strength training for individuals with knee injury. As a clinician, I’ve explored the neural underpinnings of AMI to develop treatments that target not just the muscle, but the brain-body connection. In this post, I’ll break down what AMI is, why it matters, and how a neuro-centered approach can revolutionize recovery.

What Is Arthrogenic Muscle Inhibition (AMI)?

AMI occurs when neural pathways suppress muscle activation, particularly in the quadriceps, after knee injury or surgery. This isn’t just about muscle weakness from disuse—it’s about neural inhibition. Here’s how it works:

1. Altered Signals: Sensory receptors in the knee joint send altered or excessive signals to the central nervous system (CNS) due to joint injury, pain, or swelling.

2. Inhibited Motor Neurons: These signals disrupt the motor neuron pool that controls the quadriceps, limiting their ability to contract fully.

3. Functional Weakness: Despite strengthening exercises, the muscle cannot perform optimally because the “switch” to activate motor units is stuck in the off position.

This persistent inhibition leads to muscle imbalances, asymmetry, and prolonged impairments in strength and mobility. Left unaddressed, AMI can delay recovery and reduce long-term functional outcomes.

Why AMI Matters

The quadriceps are central to knee stability and function. Persistent AMI compromises not just strength but also overall biomechanics. Worse yet, conventional interventions—like strengthening exercises or stretching—often fail to address the neurophysiological root of the problem.

Research shows that untreated AMI contributes to:

• Prolonged deficits in quadriceps strength.

• Poor recovery outcomes post-ACLR.

• Increased risk of re-injury or secondary conditions, such as osteoarthritis.

A Neuro-Centered Approach to Recovery

To effectively treat AMI, we need to rewire the brain-body connection. This means targeting the neural pathways that regulate muscle activation. Here are three key strategies to consider:

1. Open & Exploit

• Focal Joint Cooling: Cooling the knee reduces joint effusion and improves sensory input to the CNS. This creates a more favorable environment for motor activation.

• Pain Management: Addressing pain through modalities like cryotherapy or carefully prescribed medications can diminish neural inhibition.

2. Excite & Facilitate

• Neuromuscular Electrical Stimulation (NMES): NMES bypasses inhibited motor neurons, directly stimulating the quadriceps and promoting activation. Studies have shown it improves strength, activation, and muscle size post-surgery.

• Eccentric Exercises: Focus on lengthening contractions (e.g., “lowering” movements) to enhance neural and muscular adaptations. Eccentric exercises are particularly effective when combined with NMES.

• Biofeedback: Using EMG or visual feedback helps patients “see” and engage their quadriceps activation, reinforcing the neural pathways needed for recovery.

3. Force Use

• Progressive Resistance Training: Build strength by gradually increasing resistance, focusing on controlled movements.

• Blood Flow Restriction Therapy: Combining light resistance exercise with restricted blood flow enhances strength gains while minimizing strain on the joint.

Bridging the Gap: From Research to Practice

Despite advancements in understanding AMI, there’s a gap between research and clinical application. Many interventions remain underutilized, and no validated tools currently exist for diagnosing AMI at the bedside. As clinicians, we must:

• Recognize neurological drivers of muscle impairment.

• Select interventions aligned with the phase of recovery, adjusting intensity and timing for maximal impact.

• Advocate for more robust clinical tools and protocols to identify and treat AMI.

The Future of AMI Treatment

By shifting our focus to the nervous system, we can redefine recovery for patients with knee injuries. Instead of just rebuilding muscle strength, we can optimize the brain-body connection, unlocking the potential for faster and more complete recovery.

As we continue to explore neuromodulatory techniques and refine our understanding of AMI, the goal remains clear: empower patients to move confidently, rebuild strength, and return to doing what they love.

Ready to Rebuild?

If you’re navigating recovery after a knee injury or surgery, let’s take a neuro-centered approach to optimize your progress. Schedule a visit today to explore tailored interventions that address not just the muscle, but the nervous system driving it. Together, we’ll build a stronger, more functional you.