Osteoarthritis (OA) of the knee joint is a complex peripheral joint disorder with multiple risk factors. We aimed to examine the relationship between the grade of knee OA and anterior thigh length (ATL). A total of 64 geriatric patients who had no total hip or knee replacement with a BMI of ≥30 were evaluated. Patients' OA severity was determined by two independent experts from bilateral standing knee radiographs according to the Kellgren-Lawrence (KL) grade. Joint cartilage structure was assessed using ultrasonography (US). The ATL, the gastrocnemius medialis (GC), the rectus femoris (RF) and the rectus abdominis (RA) skeletal muscle thicknesses as well as the RF cross-sectional area (CSA) were measured with US. Sarcopenia was diagnosed using the handgrip strength (HGS), 5× sit-to-stand test (5xSST) and bioelectrical impedance analysis. The median (IQR) age of participants was 72 (65–88) years. Seventy-one per cent of the patients (n=46) were female. They were divided into the sarcopenic obese (31.3 %) and the non-sarcopenic obese (68.8%) groups. KL grade of all patients correlated negatively with the ATL (mm) and the thickness of GC (mm) (r= -0,517, p<0.001 and r= -0.456, p<0.001, respectively). In the sarcopenic obese and the non-sarcopenic obese groups, KL grade of the all patients was negatively correlated with ATL (mm) and thickness of GC (mm) (r= -0,986, p<0.001; r= -0.456, p=0.05 and r= -0,812, p=0.002; r= −0,427, p=0.006). KL grade negatively correlated with the RF thickness in the sarcopenic obese group (r= -0,928, p=0.008). In conclusion, OA risk may decrease as the lower extremity skeletal muscle mass increases. Acknowledgments: Feza Korkusuz MD is a member of the Turkish Academy of Sciences (TÜBA)

Background. Alterations in the neural drive to trunk muscles have been implicated in low back pain (LBP). This is supported by evidence of reduced corticospinal excitability, delayed muscle activation, reduced endurance and enhanced fatigability of these muscles; whether these changes persist during pain free periods remain unclear. Neural drive (or voluntary activation-VA) can be measured using twitch interpolation and the aim of this study is to investigate if subjects with a history of LBP show reduced VA. Methods. Twenty five subjects participated (13 with a history of LBP, 12 controls). Back extensor torque was measured using a dynamometer and bilateral electromyographic (EMG) activity was recorded from erector spinae and rectus abdominis. Transcranial magnetic stimulation of the motor cortex was applied while the subject, lying prone, performed graded voluntary back extensions. VA was calculated from the size of the twitches evoked by the TMS and EMG data were analysed for evidence of altered neural drive. Results. The LBP typical VAS pain scores were 3.39±1.76(SD), with worst pain being 5.92±2.29. There were no differences in the physical activity scores between the groups. EMG data revealed no differences in the evoked responses at varying levels of voluntary torque. VA was not significantly different between the LBP and control groups (LBP: 85.30±6.45% vs C: 80.14±11.40%). Discussion. These data show that in our cohort of subjects with a history of LBP, their ability to fully activate their back muscles maximally is not reduced. Whether subjects with current LBP exhibit reduced VA remains to be established. No conflicts of interest. Funded by Imperial College London. This abstract has not been previously published in whole or substantial part nor has it been presented previously at a national meeting