Arthrogenic Muscle Inhibition (AMI)

It’s a reflexive shutdown of muscle activation caused by changes inside the joint — usually swelling, inflammation, pain, or damage to joint receptors.

Step 1

Joint injury or irritation occurs = swelling, inflammation, or bleeding into the joint.

Step 2

This alters the firing of joint mechanoreceptors (like Ruffini endings, Pacinian corpuscles) in the capsule and ligaments.

Step 3

Those receptors send abnormal afferent signals up to the spinal cord.

Step 4 

Your nervous system interprets that as “the joint is vulnerable” = it reduces excitability of the alpha motor neurons going to the quadriceps.

Step 5

Result: even if the muscle is healthy, it can’t fully activate — it’s “inhibited.”

AMI often presents as…

extensor lag

The swelling can cause…

That swelling can cause up to 20–50% reduction in quad activation — even without any muscle damage.

How to treat

• Swelling management

• Pain modulation

• Isometrics (quad sets)

• Neuromuscular electrical stimulation (NMES)

• Tactile cues / tapping the muscle bulk whilst instructing to contract

• Early closed-chain loading

3 signs of AMI 

pain, swelling, quad contraction