Electronic Thesis and Dissertation Repository


Doctor of Philosophy




Dr. Timothy J. Doherty


PURPOSE: The purpose of this thesis was to characterize quadriceps neuromuscular dysfunction in patients with knee osteoarthritis (OA). Concerns pertaining to study design in this patient population (e.g. disease severity criteria and muscle imaging outcome measures) were also addressed.

METHODS: Five studies were undertaken using data acquired from volunteers recruited at the local institution and from participants in the public source dataset of the Osteoarthritis Initiative (http://oai.epi-ucsf.org/datarelease/). Clinical disease severity was evaluated with the Western Ontario and McMaster Osteoarthritis Index (WOMAC). Radiographic severity was evaluated with Kellgren-Lawrence Grading (KLG). Quadriceps muscle isometric strength and isotonic power were measured with dynamometry. Voluntary activation (VA) of the quadriceps was determined with the interpolated twitch technique. Information about intrinsic properties of the neuromuscular system were assessed with magnetic resonance imaging (MRI) derived measures of muscle volume, intramuscular and surface electromyography and measurement of evoked contractile properties.

RESULTS: Radiographic definition of disease severity displayed a ceiling effect and led to underestimation of quadriceps muscle weakness in patients with knee OA (Chapter 2). Quadriceps muscle isometric strength, velocity and isotonic power were reduced across a clinical spectrum of knee OA, however muscle quality (i.e. specific torque and specific power were unaffected, Chapter 3). Quadriceps whole muscle volume, measured with MRI can be reliably measured and was the primary predictor of isometric strength (Chapter 4). VA deficits were minimal in knee OA patients, even in those with severe knee pain and disability (Chapter 5). No changes in evoked contractile properties were observed across a clinical spectrum of knee OA, however average motor unit size was larger and firing rates slightly lower in patients with knee OA compared to healthy controls (Chapter 6).

CONCLUSION: This thesis provided information about the magnitude and mechanisms of quadriceps neuromuscular dysfunction in patients with knee OA, which have consequences with regard to the treatment and prognosis of this disorder. Furthermore, the information provided about the validity of commonly used predictor variables and outcome measures has implications for future study design in this disease population.