| Osteoarthritis (OA) is a common and disabling condition. Quadriceps weakness is a common impairment in persons with moderate-to-severe OA. Muscular weakness may be caused by altered activation by supraspinal pathways (measured via central activation ratio (CAR)), as well as decreased excitability of the motor cortex, termed corticospinal excitability. Little is known about how alterations in corticospinal excitability, and quadriceps activation, are related to the development of quadriceps weakness in patients with OA. Therefore, the purpose of this study was to determine differences in quadriceps strength, quadriceps activation, and corticospinal excitability in symptomatic patients with knee osteoarthritis compared to healthy controls.;A total of 23 participants volunteered for the study. Participants in the OA group (N=12, age=54.4 +/- 3.5 years, mass=85.6 +/- 4.8 kg, height=172.7 +/- 3.4 cm, WOMAC=22.7 +/- 21.3, and Tegner=3.7 +/- 1.5) and the control group (N=10, age=56.3 +/- 4.8 years, mass=74.4 +/- 3.8 kg, height=172.4 +/- 4.4 cm, WOMAC=2.5 +/- 4.2, and Tegner=5.5 +/- 1.7) performed maximal concentric isokinetic contractions and maximal isometric contractions paired with electrical stimulation to assess quadriceps strength (N*m/kg) and quadriceps activation (%). After testing quadriceps activation, we were able to measure corticospinal excitability (MEP/M max) by using transcranial magnetic stimulation (TMS) to stimulate the primary motor cortex. Data were analyzed using independent samples t-tests (p=0.05). There was statistical significance between the two groups in overall function (WOMAC: t21=-3.071, p=0.006), with the OA group reporting more pain, stiffness and difficulty performing activities of daily living than the control group. The two groups did not differ in overall level of physical activity (Tegner: t21=1.344, p=0.193). However, no statistically significant differences were found in any neuromuscular variable tested. Therefore, the results of this study do not support our hypotheses that participants with symptomatic OA would demonstrate reduced quadriceps strength, decreased quadriceps activation, and decreased corticospinal excitability when compared to healthy controls. More research needs to be completed evaluating a more symptomatic and less functional OA population. |
