Osteoarthritis (OA) is the fastest growing cause of disability worldwide. The development of new OA treatments is hampered by the complexity of the disease which over time involves multiple joint tissues including bone and cartilage. We especially don’t understand the early stages of the disease, a time when treatments may be effective. In this collaborative project we used two existing, longitudinal clinical and imaging cohorts, selected for “early” OA risk factors, and applied novel imaging (MRI) measures associated with progression of pre-symptomatic states to clinical knee OA.
Using the large American NIH Osteoarthritis Initiative cohort, which includes people at risk of developing OA, we were able to show that the three-dimensional (3D) shape of the knee bones is positively associated with later progression to total knee replacement. In addition, we found that 3D bone shape is associated with current frequent OA knee symptoms but not with incident symptoms, which may represent early OA. Using the Swedish KANON cohort, which includes 121 people who have experienced an acute anterior cruciate ligament (ACL) injury, we found that bone shape changes occur rapidly after ACL injury and are already evident at 3 months. The changes to knee bone shape post-ACL tear are similar to those reported in established knee OA. We also found that the shapes of all the bones within the knee (the femur, tibia and patella) are different in people who have just suffered an ACL injury compared to young healthy individuals without an injury. This suggests that people at risk of subsequent injury could be identified and advised to pursue sports with less chance of high impact injury.
The results of this work will inform further studies to explore the relationship of bone to OA development and progression, funded through a large collaborative European grant. Ultimately, the aim of this work is to revolutionise our understanding of the mechanisms of OA progression, define pre-OA asymptomatic and symptomatic states, identify post-traumatic OA risk factors and enable targeted OA interventions.