Arthrogenic Muscle Inhibition

Arthrogenic muscle inhibition (AMI) can occur after knee injuries or surgeries, resulting from neural inhibition that causes failure in quadricep activation. Its impact on quadricep strength is significant, as knee extensor peak torque may decrease by 80 to 90% within one to three days following knee joint surgery.

While this effect lessens over time, residual levels of AMI can persist for up to four years after the initial joint trauma. AMI also seems to be a constant presence in arthritic joint diseases, contributing to a considerable amount of quadricep muscle weakness.

Here, we look at how AMI can impact rehab after knee surgery, and how it can be effectively managed.

AMI could prove to be a barrier to rehab after knee surgery

AMI poses a major challenge in the rehabilitation process for those with arthritis or recovering from knee injuries and surgeries. By better understanding its root causes, improved treatment methods can be created that will benefit patients with knee joint issues. AMI can also hinder the process of strengthening the quadriceps, especially during the initial months following an injury or when there is significant joint damage.

The severity of AMI can depend on factors such as the angle of the knee joint, extent of joint damage, and the time since the injury. Its cause is linked to alterations in the output of sensory receptors within the joint, influenced by joint looseness, inflammation, damage to joint receptors, and swelling.

Spinal reflex pathways that may contribute to AMI include the group I nonreciprocal (Ib) inhibitory pathway, flexion reflex, and gamma-loop. There is also initial evidence that suggests higher-level pathways could play a significant role.

How can AMI be effectively managed?

Potential treatments to combat AMI include cryotherapy, transcutaneous electrical nerve stimulation, and neuromuscular electrical stimulation. In cases where there is strong inflammation alongside joint issues, nonsteroidal anti-inflammatory drugs and intra-articular corticosteroids (injected into the joint) may also be effective.

A recent study has shown that cryotherapy and physical therapy can help to effectively manage AMI. A comprehensive review of intervention effectiveness was carried out, following the guidelines and methodologies established by Arksey and O’Malley, as well as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

The search terms used included a range of keywords related to knee injuries, quadriceps activation, arthrogenic muscle inhibition, and neuroplasticity. Each article’s risk of bias was assessed using the PEDro criteria, while the overall quality of evidence for each intervention was evaluated using the GRADE approach.

The review found moderate-quality evidence supporting the effectiveness of cryotherapy and physical exercises in boosting quadriceps activation after ACL injuries and reconstruction. As a result, these treatment methods are recommended for managing AMI.

Mr Shah Punwar has occasionally seen AMI in patients after knee surgery. Book an appointment today if you suspect you have AMI following a recent surgery, or to discuss the risk involved if you are due to undergo a knee procedure.

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