AB1368 ULTRASONOGRAPHIC EVALUATION OF THE KNEE AND MUSCLE ARCHITECTURE IN OSTEOARTHRITIS AND RHEUMATOID ARTHRITIS

Abstract

BackgroundInvolvement of lower extremity joints in both rheumatoid arthritis (RA) and osteoarthritis (OA) is an important cause of declined functional status. Deterioration of skeletal muscle performance further contributes to disability. Quadriceps muscle plays an important role in most daily activities. Measuring thickness and pennation angle of quadriceps compartments can provide knowledge regarding quadriceps condition.ObjectivesAim is to investigate structural and inflammatory changes in knee joint and architecture of quadriceps muscle in RA, knee OA patients and a group of healthy subjects.MethodsTwenty RA patients and 20 knee OA patients with radiographic disease meeting Kellgren-Lawrence grade 2 and above were consecutively recruited, in absence of exclusion criteria. 20 healthy volunteers with similar demographics were recruited as control group. Knee symptoms and disability were evaluated by Lequesne Knee Index (LKI). Disease activity was evaluated by DAS28-CRP in RA patients. Quadriceps muscle was evaluated by ultrasonographic measurements of muscle thickness, subcutaneous fat tissue thickness and pennation angle of vastus muscles. Suprapatellar, lateral and medial compartments of knee joint were examined for effusion, synovial hypertrophy, power Doppler (PD) activity and degenerative changes.ResultsDemographics and clinical features of subjects and results of ultrasonographic evaluation are presented in Table 1. LKI scores were significantly higher in OA patients when compared to RA patients (p=0.004). Rate of degenerative changes was increased in RA and OA groups in comparison to controls (p=0.013). None of the subjects had PD activity. No differences were observed in thickness of rectus femoris, vastus muscles and subcutaneous fat between groups. Vastus medialis and intermedius pennation angles were reduced in OA and RA groups when compared to controls, but reached statistical significance only in vastus intermedius (3.56 ± 6.37 vs 4.89 ± 7.14 vs 7.29 ± 4.93, p=0.038).Table 1.Demographics, clinical features and ultrasonographic findings of subjectsOA (n=20)RA (n=20)Control (n=20)pAge, years¶58.44 ± 6.6854.67 ± 7.1555.11 ± 5.890.178Gender, femaleµ17 (85)15 (75)16 (80)0.732BMI¶30.05 ± 3.8828.29 ± 4.7828.27 ± 3.340.343Duration of diagnosis, months¶11.95 ± 17.1514.80 ± 8.500.023LKI¶9.37 ± 2.656.95 ± 3.380.004DAS28-CRP¶2.59 ± 1.10Presence of effusion µ9 (45)9 (45)4 (20)0.166Presence of SH µ9 (45)11 (55)8 (40)0.626Presence of degeneration µ16 (80)13 (65)7 (35)0.013Muscle thickness, mm¶ VM14.09 ± 4.1715.38 ± 5.1514.57 ± 3.410.243 VL17.17 ± 3.5316.96 ± 4.9816.66 ± 3.180.985 VI10.54 ± 2.6510.49 ± 3.3210.67 ± 1.830.926 RF13.01 ± 3.9213.74 ± 3.7813.63 ± 3.490.879SFT thickness, mm¶12.59 ± 5.7913.81 ± 7.1012.53 ± 5.200.969Pennation angle, degree ¶ VM5.50 ± 7.016.94 ± 8.299.05 ± 5.100.244 VL13.61 ± 5.1513.44 ± 3.4013.29 ± 3.250.703 VI3.56 ± 6.374.89 ± 7.147.29 ± 4.930.038¶: mean ± SD, µ: number (%),LKI: Lequesne Knee Index, KL: Kellgren – Lawrence grade, SH: synovial hypertrophy, VM: vastus medialis, VL: vastus lateralis, VI: vastus intermedius, RF: rectus femoris, SFT: subcutaneous fat tissueConclusionIn our study ultrasound evaluation findings of knee joint and quadriceps muscle were similar between knee OA and RA patients.VM and VI pennation were reduced when compared to healthy subjects in both groups. These findings may indicate a similar degree of functional impairment in OA and RA due to knee joint involvement.