Elucidating the Role of Joint Disuse in the Development of Osteoarthritis following Return to High-Impact Loading
Abstract
Our joints constantly experience weight-bearing and mechanical forces from the activities we pursue. For example, when we stand, the weight of our upper body places a compressive load on our knee joint. When we serve a tennis ball, the impact between the racket and the ball places a twisting or shearing load on our elbow joint. In normal circumstances, we need these forces on our joints, as loading joints stimulates the processes the body uses to maintain and repair our joint tissues, including the cartilage in our joints. If we do not use our joints, these maintenance and repair processes do not get activated and breakdown of the joint tissue occurs, leading to damage to the joint. There are a number of reasons why a joint would not be loaded, including prolonged periods of bed rest or because the joint was immobilized, such as would occur when a cast is placed on a limb to allow a fracture to heal. Bed rest could occur due to a number of reasons, including recovery from serious injury such as an automobile accident, or in the case of military personnel, due to injury incurred in the line of duty, recovery from severe viral infections, or during pregnancy, just to name a few. While "normal loading" is good for joints, excessive loading can cause damage to the joint. For example, military personnel who routinely carry loads in excess of 100 pounds for long periods of time could be considered to be overloading their joints. This damage could include thinning of the cartilage covering the joint surface, tearing of that same cartilage or damage to the tendons and ligaments that hold the joint together. In the latter case, this can cause slipping of one bone surface over another bone surface in the joint, leading to damage to the cartilage in the joint from shearing loads. Over time, this damage will accumulate and can lead to osteoarthritis in the overused joint. Most of the time after a period of immobility, a person would return to normal loading on the joint (i.e., walking) and the normal maintenance and repair processes would correct the damage done to the joint after the bed rest. However, people with jobs that are physically demanding (such as movers or construction workers, elite athletes, and military personnel who are returning to duty assignments involving intense physical activity) will be transitioning from a period of no joint use (leading to joint damage) to a period of overuse of the joint (leading to joint damage). Anecdotally, there are reports from doctors suggesting that these people going from no joint use to overuse are at a higher risk for developing osteoarthritis, but this possibility has never been examined scientifically in detail, and this study has been designed to correct this gap in our knowledge. This study is broken into two halves. In the first half, we will create a situation whereby the hind limbs of mice are unloaded (or not bearing weight) to simulate bed rest. We will then examine the damage to the joint that occurs just from bed rest. Next we will examine the recovery/repair that occurs in the joint after simulated bed rest followed by a recovery period during which the mice are allowed to walk around normally for 2 to 4 weeks. Lastly, we will examine what happens to the joint after simulated bed rest followed by overloading to the joint. We will examine the impact of both high-intensity compressive loading and shearing loads applied 5 days a week for 2-4 weeks on the joint. Some mice will be allowed to return to normal activity after this period of overloading. Collectively, this will allow us to measure the cumulative impact of no loading on the joint plus overloading of the joint, and if overloading is stopped, can the joint recover from this or is the damage too much for the body to heal from, suggesting that osteoarthritis would follow from such a pattern of joint use. In the second half of the grant, we will look at overloading of the joint in a different
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 29, 2016
- Source ID
- W81XWH1510371
Entities
People
- Douglas E. Adams
Organizations
- United States Army
- University of Connecticut Health Center