Musculoskeletal injuries and pain are a significant cause of disability. This is a worldwide problem.
Just one common musculoskeletal issue, osteoarthritis, affects more than three million Australians. Osteoarthritis also has a formidable personal burden with more years lived with disability than type 2 diabetes, ischaemic heart disease or stroke. Osteoarthritis leaves people unable to manage basic activities of daily living.
Pharmacological management is one of the most common strategies to assist people with osteoarthritis. However, pharmacological management has poor long-term outcomes and thousands of people progress to joint replacements every year. This results in a huge economic burden with osteoarthritis costing the Australian economy hundreds of millions of dollars a year.
Another example is the common musculoskeletal condition Achilles tendinopathy. Exercise rehabilitation is universally recommended as it has a significant effect on improving patient-reported function. However, even though exercise rehabilitation is accepted as the gold standard, it is clear that even after months of treatment, many patients still have residual symptoms even though they have significantly improved.
Therefore, to ensure we can improve the outcomes of treatment for our patients to achieve complete resolution of symptoms, we need to understand why some fail to improve and how we can amend our management.
It is the case that people with musculoskeletal injury are unable to fully activate their muscles. The brain acts like a car, an accelerator contracts a muscle, a brake stops it. We know that people with musculoskeletal pain cannot ‘release the brake’ (termed cortical inhibition) and even when contracting at their fullest, termed maximal voluntary activation, they are unable to generate what should be maximal force.
In hip and knee osteoarthritis, large differences in voluntary activation exist between people with osteoarthritis and healthy controls, as well as moderate differences between the symptomatic and asymptomatic sides of the same person. This is a massive problem as this cortical inhibition is directly associated with osteoarthritis pain severity and disability.
Electrical brain and muscle stimulation
Non-invasive electrical brain stimulation (e.g. transcranial direct current stimulation) and muscle stimulation (neuromuscular electrical stimulation) are not new concepts. Electrical brain and muscle stimulation has been used safely for decades in other conditions (e.g. following stroke) to improve patient outcomes.
Non-invasive electrical brain stimulation improves the cortical inhibition present following musculoskeletal injury, facilitating peripheral muscle activation and improving overall motor output. Furthermore, non-invasive electrical brain stimulation has also been shown to activate the body’s natural analgesic mechanisms, directly reducing pain.
However, despite this evidence electrical stimulation of the brain and muscle are rarely used in Australian clinical practice for people with hip, knee or ankle injuries or pain.
Improved clinical outcomes using electrical stimulation
Recent research has been able to show that electrical stimulation to either the brain or peripheral muscles can improve the outcomes of exercise rehabilitation of people with musculoskeletal pain. Following anterior cruciate ligament (ACL) reconstruction, utilising peripheral nerve stimulation can improve outcomes following surgery with faster recovery of muscle strength.
Pain, disability and function in people with knee osteoarthritis have also been shown to improve by as much as 60% when combining brain stimulation with exercise, compared to sham brain stimulation and exercise. Therefore, non-invasive electrical brain stimulation should be considered as a legitimate option in the management of people with musculoskeletal pain such as osteoarthritis or tendinopathy.
We know that our current outcomes for people with musculoskeletal pain are not good enough and we need to do better to reduce the number of people living with disability from musculoskeletal pain. However, electrical brain and muscle stimulation is an exciting avenue to address known impairments present in musculoskeletal pain. Utilising electrical brain and muscle stimulation should be encouraged due to the low side-effect profiles and evidence supporting its effects.
Key messages
- People with musculoskeletal pain and injury cannot fully activate their muscles
- Inability to fully activate muscles is directly associated with pain and disability
- Innovative approaches such as electrical brain stimulation and peripheral nerve stimulation can improve exercise rehabilitation outcomes.
ED: Dr Murphy is a postdoctoral clinical researcher at the Nutrition and Health innovation Research Institute at Edith Cowan University.
Author competing interests – The author is supported by a Raine Medical Research Foundation Priming Grant as well as a WA Department of Health Innovation Fellowship and a Near-Miss Award.