Purpose: To study the associations between leisure time physical activity level and estimated biochemical composition of tibiofemoral cartilage in postmenopausal women with mild knee osteoarthritis (OA) after 4‐month aquatic resistance training intervention. Methods: Originally 87 volunteer postmenopausal women 60e68 years of age with mild knee OA (Kellgren Lawrence I or II) participated in the 4‐month aquatic training randomised controlled trial (ISRCTN65346593). After intervention, 76 (87%) of them completed the 12‐month follow‐up study. Physical activity was measured during the 12‐month follow‐up period using a leisure time physical activity diary from which metabolic equivalent task hours (METh) per month were calculated. Participants were divided into three physical activity tertiles based on average monthly METh: 1) lowest (n=25), 2) middle (n=25) and 3) highest (n=26). The biochemical composition of both weight bearing and non‐weight bearing regions of the tibiofemoral cartilage was estimated using transverse relaxation time (T2) and delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC) index. Single sagittal slices at the centre of the medial and lateral femoral condyles were manually segmented using an in‐house MATLAB application with built‐in motion correction for dGEMRIC (Mathworks, Inc. Natick, MA, USA) (Figure 1). Secondary outcomes were cardiorespiratory fitness, isometric knee flexion and extension force and knee injury and osteoarthritis outcome score (KOOS) questionnaire. The associations between physical activity tertiles and outcomes was analysed using generalised linear models. (Figure Presented) Results: There was a significant linear association between physical activity level and increase in dGEMRIC index in posterior region of interest (ROI) of the lateral (p for linearity=0.003) and medial (p=0.006) femoral condyles cartilage in 12‐month follow‐up. More specifically, in the superficial and deep posterior ROIs of the lateral femoral codyle cartilage (p=0.004) and (p=0.007), respectively, and in the superficial posterior ROI of medial femoral condyle cartilage (p<0.001) (Table 1). No linear association was observed between leisure time physical activity level and T2 relaxation time or physical performance traits and self‐assessed impact of OA (KOOS) in 12‐ months. Conclusions: These results suggests that moderate to vigorous intensity leisure time physical activity level is associated with beneficial regional changes in estimated knee articular cartilage glycosaminoglycan content in 12 months. These results have an important role when assessing physical activity levels for cartilage quality related exercise intervention studies and also in clinical rehabilitation in postmenopausal women with mild knee OA.
Munukka, M., Waller, B., Rantalainen, T., Häkkinen, A., Nieminen, M. T., Lammentausta, E., … Heinonen, A. (2016). Association between leisure time physical activity level and articular cartilage in postmenopausal women with mild knee osteoarthritis: a 12-month follow-up study after 4-month intervention. Osteoarthritis and Cartilage, 24, S364–S365. https://doi.org/10.1016/j.joca.2016.01.654