Special Issue: Injury and post‐traumatic osteoarthritis

As a sports medicine practitioner, I frequently see patients with various sports injuries, including acute knee ligament injury, patellar dislocations, subluxations and dislocations of the shoulder, and ankle sprains. In addition to injury to the stabilizing ligaments and capsular structures, there is frequently concomitant injury to the articular surface. It is becoming increasingly evident that even a single transarticular load, with no macroscopically evident injury, can initiate a process resulting in eventual cartilage breakdown and post‐traumatic osteoarthritis (PTOA).

At the same time, our treatment options for these injuries continues to advance, with improvements in surgical management and rehabilitation, allowing more and more of these injured athletes to return to a high level of activity and competition. Consequently, sequelae of articular surface injury and eventual post‐traumatic osteoarthritis have emerged as critically important problems for the sports medicine practitioner. With increasing numbers of young individuals participating in sports with greater frequency and intensity, PTOA has become recognized as perhaps the most important factor in managing sports injuries. For example, I will commonly see a 15‐year‐old female with an ACL injury or a 17‐year‐old male high school football player with a shoulder dislocation. Even though the sequelae of cartilage injury and PTOA may not occur for 10 to 15 years, we are seeing patients in their late 20s and early 30s with significant degenerative joint disease. For the practitioner managing these injuries, no longer is our job just to treat the initial injury and get the athlete back to the field of play. If is now clear that our job is to recognize and treat the articular surface injury, and devise new treatment approaches to mitigate and ideally prevent the long‐term issues related to PTOA. This special issue of the Journal of Orthopaedic Research begins to explore fundamental issues related to PTOA.

It has been established that the pathologic process of PTOA can be initiated at the time of the acute injury. Consequently, the sports medicine physician, athletic trainer, or other practitioner who initially evaluates and manages the injured athlete is in a position to recognize and potentially initiate management strategies at “time zero” that may mitigate or prevent progressive cartilage degenerative changes. Advances in imaging as well as identification of biomarkers in synovial fluid, serum, and urine may ultimately allow earlier detection of articular cartilage injury. At the same time, further studies are needed to identify novel and innovative treatment approaches that can be initiated immediately at the time of injury in an effort to potentially forestall or even prevent the cascade of pathophysiologic processes that result in PTOA. In this special issue of the Journal of Orthopedic Research you will find a number of studies in the area of imaging biomarkers and biospecimen biomarkers for early detection of joint injury. Other papers describe the underlying pathophysiologic process of early cartilage injury and the relationship to eventual PTOA. The physician, athletic trainer, or other practitioner who sees the athlete on the sidelines or in the training room may be in the best position to initiate appropriate management to prevent PTOA. In this way our job has become much more than just getting the athlete back on the field of play. The clinical and basic science information contained in this special edition will provide a foundation for further studies to identify novel treatments that can be initiated at the time of injury.

Another group of “athletes” in whom PTOA is becoming an increasingly important problem is our military veterans. Soft tissue injuries similar to common sports injuries occur frequently in our service members. Similar to athletes, these are often young individuals who return to a high level of activity. Thus, this is another important group that will benefit from further information related to early diagnosis and management of PTOA.

Careful study of patients with acute traumatic injuries can also provide important insights into the basic pathophysiologic process of cartilage degeneration and eventual arthritis. Because the pathophysiologic process of osteoarthritis develops gradually over a long period of time and is typically clinically silent in the early phases, typical patients with OA do not present for treatment until the process is well‐established. This makes it very challenging to understand the timing of onset, etiologic factors, and natural history. Symptoms do not typically develop until the process is chronic and very well‐established, making it impossible to study the early events involved in the pathophysiologic process. In contrast, in young patients with acute injury we can identify the exact timing of the injury. Furthermore, it can typically be assumed that this was a normal joint prior to the injury in these young patients. Such patients can then be identified and followed prospectively. Because they are evaluated at the time of injury, we also have the opportunity to intervene at “time zero”. In this way the study of patients with acute joint injury provides a unique human model to study the development of osteoarthritis. This special edition of the Journal of Orthopedic Research contains several animal models that recapitulate these injuries in humans, and allow further in‐depth study of the pathophysiology of PTOA.

Our hope and expectation is that this collection of papers related to the clinical and basic science issues related to post‐traumatic osteoarthritis will serve as a springboard for further research in this area.