Background:Achilles tendon (AT) ruptures are one of the most common tendon ruptures, but there have been no studies investigating these injuries in the United States (US) using data representative of the entire US population.Purpose/Hypothesis:The purpose of this study was to determine the incidence and risk factors for AT ruptures in the US. We hypothesized that male sex, older age, and sport participation would increase the risk for AT ruptures.Study Design:Descriptive epidemiology study.Methods:All patients presenting to an emergency department with ruptured AT in the US from 2012 through 2016 were selected from the National Electronic Injury Surveillance System (NEISS) database. Incidence was calculated for sex, race, and age. AT ruptures were characterized based on the mechanism of injury, with subanalyses performed on sport-related AT ruptures to examine sex-, race-, and age-related differences.Results:From 2012 to 2016, a significant increase in the incidence of AT ruptures was observed, from 1.8 per 100,000 person-years in 2012 to 2.5 per 100,000 person-years in 2016 (P < .01), for an overall incidence of 2.1 per 100,000 person-years. The majority of AT ruptures occurred in male compared with female patients, with an incidence rate ratio of 3.5 (P < .01). The largest overall incidence of AT ruptures occurred in those aged 20-39 years for male patients (5.6/100,000 person-years) and in those aged 40-59 years for female patients (1.2/100,000 person-years). The largest rise in the incidence of AT ruptures during the study period was observed in patients aged 40-59 years (78% increase). The most common injury mechanism was participation in a sport or recreational activity (81.9% of all injuries), with basketball being the most common overall cause of AT ruptures.Conclusion:While AT ruptures in the US most commonly occur in young male patients (20-39 years old), the largest rise in the incidence was observed in middle-aged patients (40-59 years old), with participation in recreational sports being the most likely mechanism. Recognizing high-risk patients can help physicians counsel them and recommend strategies for injury prevention.

Background: There is a paucity of literature regarding risk factors and mechanisms of Achilles tendon (AT) ruptures in the National Basketball Association (NBA). Purpose: To identify the risk factors and outcomes of AT ruptures in NBA athletes. Furthermore, using video analysis, to characterize the mechanisms of rupture by identifying the most common playing situations and lower extremity positions at the time of injury. Study Design: Descriptive epidemiology study. Methods: AT ruptures in the NBA that occurred between the seasons of 1969-1970 and 2017-2018 were identified. Player data collected included age, position, body mass index, total games started before and after injury, and Player Efficiency Rating. Injury-related variables collected included date of injury, laterality, minutes played before injury, operative versus nonoperative treatment, and time to return to play. Available video footage was analyzed for the mechanism and body position at the time of injury. Univariable and multivariable linear regression was used to compare changes in performance before and after AT rupture. Statistical significance was set at P < .05. Results: Forty-four ruptures were identified between 1970 and 2018. The mean age was 28.3 years, with players averaging 6.8 seasons before AT rupture. AT ruptures were most prevalent during early-season game play (27.3%), followed by preseason (18.2%) and late season (18.2%). More than a third (36.8%) of players either did not return to play or started in fewer than 10 games in the remainder of their career, with 21% of ruptures leading to retirement. The mean time to return to play was 10.5 months. The Player Efficiency Rating declined by an average of 2.9 points (range, –11.5 to +2.3) ( P < .001). Analysis of available injury footage (n = 12) demonstrated all ruptures to be noncontact in nature, most commonly occurring just before takeoff as the player began to push off from a stopped position, with the foot in dorsiflexion, the knee in early flexion, and the hip in extension. Conclusion: In the NBA, a majority of AT ruptures occur early in the season, in veteran players, with almost half not returning to play or starting fewer than 10 games in the remainder of their career. The most common mechanism of injury is taking off from a stopped position just before toe-off in a dorsiflexed foot.

Adult human articular cartilage harbors a population of CD166+ mesenchymal stem cell-like progenitors that become more numerous during osteoarthritis (OA). While their role is not well understood, here we report that they are indeed part of cellular clusters formed in OA cartilage, which is a pathological hallmark of this disease. We hypothesize that these cells, termed OA mesenchymal stem cells (OA-MSCs), contribute to OA pathogenesis. To test this hypothesis, we generated and characterized multiple clonally derived stable/immortalized human OA-MSC cell lines, which exhibited the following properties. Firstly, two mesenchymal stem cell populations exist in human OA cartilage. While both populations are multi-potent, one preferentially undergoes chondrogenesis while the other exhibits higher osteogenesis potential. Secondly, both OA-MSCs exhibit significantly higher expression of hypertrophic OA cartilage markers COL10A1 and RUNX2, compared to OA chondrocytes. Induction of chondrogenesis in OA-MSCs further stimulated COL10A1 expression and MMP-13 release, suggesting that they contribute to OA phenotypes. Finally, knocking down RUNX2 is insufficient to inhibit COL10A1 in OA-MSCs and also requires simultaneous knockdown of NOTCH1 thereby suggesting altered gene regulation in OA stem cells in comparison to chondrocytes. Overall, our findings suggest that OA-MSCs may drive pathogenesis of cartilage degeneration and should therefore be a novel cell target for OA therapy.