The Isolated Mechanical Effect Of Walking In Late Pregnancy May Contribute To The Risk For Knee Osteoarthritis Over The Lifetime

Evidence suggests that pregnancy (PREG) increases a woman’s risk of knee osteoarthritis (OA). While understanding the underlying causes or association with PREG is complex, the mechanical load on cartilage during walking appears to be important to the initiation and progression of OA. PURPOSE It is currently unknown if mechanical changes associated with PREG, which may be substantial in magnitude but may be limited in duration, can explain the OA risk since it is diagnosed later in life. Therefore, we aimed to model the effect of walking in late PREG on cartilage loading and simulate the mechanical effect of PREG/PREGs, experienced at different times over the lifetime, on knee joint health. METHODS Static optimization, joint contact force modeling and a mechanical model of cartilage response were used to estimate loading at a self-selected speed for 10 PREG in 3rd trimester and 10 non-PREG controls. Probabilistic models of cartilage fatigue and failure simulated cases of 0-3 PREGs separated by 2 years with first births at age 23 or 30 and estimated the probability of structural failure at age 55, the median age of first diagnosis of OA. Peak PREG/non-PREG cartilage strain in stance and estimates of cartilage failure probability were compared using paired t-tests. RESULTS PREG women experienced additional peak strain on knee cartilage (0.29, non-PREG: 0.23 p = 0.004) which resulted in a greater estimates of cartilage failure probability when virtual subjects experienced 1, 2, or 3 pregnancies starting at age 23 (average increases of 7.7%, 13.4% and 15.5% from the never-PREG condition, respectively all p < 0.01) with differential effects when women experience multiple PREGs later in their lifetime (6.9% greater risk when experiencing 2 PREGs starting at age 30 p < 0.01). CONCLUSION AND SIGNIFANCE/NOVELTY: Simulated PREG increased the probability of cartilage failure and there was additional risk when experiencing multiple PREGs later in life. Although understanding the underlying causes of knee OA is complex the mechanical load on cartilage during PREG is elevated and may, in part, contribute to the increased risk of knee OA for this population. Results may have implications for PREG physical activity and future research may aim to determine if gait modifications can be used to reduce joint loading and possibly reduce knee OA risk. ASB grant in aid award, UMD Kinesiology Grip Award