Determining the cortico-reticulospinal responses following cross education in end stage knee osteoarthritis.

Osteoarthritis (OA) affects 2.1 million adults in Australia, with the knee (KOA) being the most affected joint. By 2051, 3.15 million Australians will have OA. Motor impairment (loss of knee-extensor strength) and pain are key features of moderate-severe KOA, making treatment challenging and functional outcomes poor. Along with chronic pain and changes in knee-joint structure, people with KOA experience changes in sensory-motor function, with data showing the functional organisation of the motor cortex (M1) is different in KOA patients when compared to aged-matched controls. These changes are due to motor impairment and chronic pain. People with KOA are unable to rehabilitate this side due to poor strength and pain, limiting rehabilitation outcomes. An alternative, less labour-intensive approach, is to train the non-affected limb and improve muscle-strength of the affected-KOA limb by an innovative technique called cross-education (CE). CE is the process whereby strength-training one limb increases muscle-strength and function of the opposite untrained-limb. Two mechanisms could underlie these improvements: increased motor cortex activity ipsilateral (iM1) to the KOA-limb, and/or functional reorganisation of the corticomotor-projections to the KOA-limb; both mechanisms are emergent properties of CE. To distinguish between these possibilities, new methods are required that allow us to identify which mechanism is at play and whether functional reorganisation of the motor cortex occurs following a simple CE intervention in KOA patients. The proposed PhD will investigate CE as a new treatment for KOA and study the associated neural mechanisms to further the knowledge about CE in clinical populations. CE could be the key to developing a simple, effective and translatable rehabilitation program for KOA patients: The CE effect is specific to the contralateral muscle, but not restricted to particular muscle groups, ages or genders. CE may have benefits in clinical populations such as stroke, anterior cruciate ligament injury, fracture and potentially KOA. CE in a KOA cohort is highly viable because unilateral KOA is present in 76% of patients; overtime, KOA becomes a symmetrical disease in 100% of patients. Targeting the non-affected limb will not only improve function of the trained limb, but also the untrained KOA limb, leading to a reduced risk of bilateral KOA. In summary, a loss in muscle-strength and increased pain are key features of KOA. CE is capable of improving muscle-strength of the trained and untrained-limbs, making it a promising new treatment. Therefore, the primary aim of this research is to determine whether CE is effective in treating symptoms of KOA and to explore the effect of CE on neuroplasticity in descending motor pathways as a mechanism for symptom improvement.