Treating the Neural Origins of Disability following Knee Injury

Knee pathologies rank among the most common, most debilitating, and the most costly musculoskeletal conditions in the United States each year. Unfortunately, injury to this major weight-bearing joint often affects a person’s ability to walk, run, and participate in adequate physical activity. Patients with chronic knee conditions and physical disability are often at higher risk of developing dangerous inactivity related diseases such as obesity, diabetes and cardiovascular disease. Therefore, it is critical to develop treatments that keep patients with knee injury and chronic knee conditions physical active.

Neuromuscular alterations in muscles surrounding the injured knee are a major hindrance to improving/maintaining patient function. Neuromuscular alterations following knee injury often manifest as neural inhibition, or inability to contract the uninjured quadriceps musculature. Without proper neuromuscular function of the quadriceps, patients with knee injury often exhibit altered walking or running mechanics. Altered biomechanics may lead to chronic joint degeneration or a hastened progression of knee osteoarthritis. Previously, we have outlined the theoretical framework contributing to neuromuscular alterations following knee injury and the biomechanical cost of these alterations in detail. See – Pietrosimone BG, McLeod MM, Lepley AS. A theoretical framework for understanding neuromuscular response to lower extremity joint injury. Sports Health. 2012;4(1):31-35. PMID: 23016066.

Disinhibitory Intervention Model

Theoretical model linking the development of disinhibitory interventions to improving quality of life

We are simultaneously trying to: 1) better understand the mechanisms behind this neuromuscular response to joint injury and 2) doing our best to develop interventions to treat patients with this problem. For many people with neuromuscular alterations following knee injury, traditional therapeutic exercise does not address the underlying neural genesis of the disease. We, and other laboratories, have tested different therapies that seem to show promise in specifically targeting neuromuscular dysfunction for the purpose of augmenting traditional therapeutic exercise and improving patient outcomes.  I have recently worked Matthew Harkey MS ATC, who is a first year Human Movement Science PhD student, and Dr. Phillip Gribble, a faculty member at the University of Toledo, on a Systematic Review that looks to determine the most effective therapeutic interventions for increasing neuromuscular control of the quadriceps.  See – Harkey MS, Gribble PA, Pietrosimone BG. Disinhibitory Interventions and Voluntary Quadriceps Activation: A Systematic Review. J Athl Train. 2014 Feb 3. [Epub ahead of print] PMID: 24490843

Why did you do this study?

 We conducted the systematic review in order to provide clinicians with the currently most effective interventions for specifically combating neuromuscular dysfunction of the quadriceps. We felt that these data would be important for Athletic Trainers and Physical Therapists to know in order to best treat neuromuscular alterations following knee injury. Many of the studied modalities are easily accessible in current clinical settings; we hoped that the current systematic review would shed light on these modalities, and provide new indications (treating neuromuscular alterations) for many modalities with which clinicians are already familiar.

What did you do in this study?

Transcranial Magnetic Stimulation (TMS)

Transcranial Magnetic Stimulation (TMS)

We searched Web of Science from January 1, 1965 through September 27, 2012, using the key words such as: “quadriceps activation” and “transcutaneous electrical nerve stimulation”, “transcranial magnetic stimulation,” “cryotherapy”, “focal joint cooling”, “joint mobilization”, “joint mobilization”, “joint manipulation”, “manual therapy”, and “neuromuscular electrical stimulation”. We included studies that evaluated the effect of disinhibitory interventions on volitional quadriceps activation, which is a recognized measure of neuromuscular function. Effect sizes were calculated from voluntary quadriceps activation means and standard deviations measured at baseline and at all available post intervention time points from each study in order to compare the different interventions across laboratories.

What did you do and what did you find in this study?

Screen Shot 2014-03-01 at 8.36.39 AM

Transcutaneous Electrical Nerve Stimulation (TENS)

We found ten studies were grouped into 5 categories based on intervention type: manual therapy (4 studies), transcutaneous electrical nerve stimulation (2 studies), cryotherapy (2 studies), neuromuscular electrical stimulation (2 studies), and transcranial magnetic stimulation (1 study).  Transcutaneous electrical nerve stimulation (TENS) demonstrated the strongest immediate and long-term effects and transcranial magnetic stimulation of the brain had moderate immediate effects in improving voluntary quadriceps activation, whereas manual therapy elicited only weak immediate effects. Neuromuscular electrical stimulation produced weak negative to strong positive effects over a period of 3 weeks to 6 months.

How do these findings impact the public?

The most current literature suggests that TENS used in conjunction with therapeutic exercise has the ability to best improve quadriceps neuromuscular alterations following joint injury. TENS is a relatively inexpensive and safe treatment, which is normally used as a non-pharmacological treatment for pain. Recent evidence indicates that TENS can be used in conjunction with strength training to improve neuromuscular function in patients with knee injury.

EXSS Impact

Jan 20 blog - exercise oncology picCurrently, EXSS faculty and students are continuing to conduct research to identify patients that would best respond to neuromuscular interventions following knee injury. Additionally, we are developing new modalities and plan to test TENS in larger patient populations.  We look forward to providing updates on these new directions in the near future. As for now, try incorporating TENS into your traditional therapeutic exercise interventions for patients with knee injury. Let me know your results!! brian@unc.edu

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