Epidemiology of ankle sprains and chronic ankle instability

Objective: To provide a focused overview of the existing literature on the epidemiology of acute ankle sprains (lateral, medial, and high/syndesmotic) with an emphasis on incidence studies from the United States. In addition, we provide a brief overview of chronic ankle instability (CAI), posttraumatic osteoarthritis, and injury prevention to contribute to our understanding of the epidemiology of these injuries and the current state of the science on ankle sprains and ankle instability in sports medicine. Background: Acute ankle sprains are one of the most common musculoskeletal injuries, with a high incidence among physically active individuals. Additionally, acute ankle sprains have a high recurrence rate, which is associated with the development of CAI. Understanding the epidemiology of these injuries is important for improving patients’ musculoskeletal health and reducing the burden of lower limb musculoskeletal conditions. Description: Acute ankle-sprain incidence rates are summarized among the general population, as well as among physically active populations, including organized athletics and military personnel, with a focus on incidence in the United States. The link between a prior ankle sprain and a future acute ankle sprain is described. We also discuss the association between the incident ankle sprain and adverse, long-term outcomes such as CAI and posttraumatic osteoarthritis. Finally, we summarize injury-prevention successes and future directions for research and prevention. Clinical Applications: This information is useful for health care providers to understand the expected incidence rates of acute ankle sprains, be aware of the association between ankle sprains and negative short- and long-term outcomes, and be familiar with existing injury-prevention programs

Osteoarthritis prevalence in retired national football league players with a history of ankle injuries and surgery

Context: Ankle injuries are common at all levels of American football, and retired National Football League (NFL) players have a high prevalence of osteoarthritis (OA), but little is known about how ankle injuries influence OA prevalence and daily activities in this population or how surgical interventions for such injuries alter the risk of OA. Objective: To examine (1) the association of ankle-injury history with OA prevalence, (2) the association of surgical intervention after ankle injury with OA prevalence, and (3) the relationships among ankle injuries, reported OA, and daily activities in retired NFL players. Design: Case-control study. Setting: Survey. Patients or Other Participants: Data from the Retired NFL Players General Health Survey. Main Outcome Measure(s): We created a 7-category main exposure variable that differentiated respondents by football-related ankle injury and surgical intervention. Multivariable binomial regression models were used to estimate prevalence ratios and 95% confidence intervals. Among those reporting OA, we examined the distribution of responses regarding whether OA affected daily activities. Results: Among the 2446 respondents, 920 participants experienced OA in any joint during their lifetime. Compared with those reporting no ankle injuries, the prevalence of OA was higher among those with a history of ankle injury. Also, the prevalence of OA was higher among those who had undergone surgery versus those who had not. The number of retired NFL players who reported that OA often affected their daily activities increased with the number of ankle injuries. Conclusions: Among former NFL players, a history of ankle injury increased the prevalence of OA. More ankle injuries increased the probability that OA negatively affected daily activities. Future prospective research is needed to better determine the influence of surgical intervention at the ankle or foot on OA

Talar and Subtalar T1ρ Relaxation Times in Limbs with and without Chronic Ankle Instability

Objective: The primary aim was to determine differences in talocrural and subtalar joint (STJ) articular cartilage composition, using T1ρ magnetic resonance imaging (MRI) relaxation times, between limbs in individuals with unilateral chronic ankle instability (CAI) and compare with an uninjured control. Our secondary purpose was to determine the association between talocrural and STJ composition in limbs with and without CAI. Design: T1ρ MRI relaxation times were collected on 15 CAI (11 females, 21.13 ± 1.81 years, body mass index [BMI] = 23.96 ± 2.74 kg/m2) and 15 uninjured control individuals (11 females, 21.07 ± 2.55 years, BMI = 24.59 ± 3.44 kg/m2). Talocrural cartilage was segmented manually to identify the overall talar dome. The SJT cartilage was segmented manually to identify the anterior, medial, and posterior regions of interest consistent with STJ anatomical articulations. For each segmented area, a T1ρ relaxation time mean and variability value was calculated. Greater T1ρ relaxation times were interpreted as decreased proteoglycan content. Results: Individuals with CAI demonstrated a higher involved limb talocrural T1ρ mean and variability relative to their contralateral limb (P 0.05), talocrural and posterior STJ composition measures were positively associated. Conclusions: Individuals with CAI have lower proteoglycan content in both the talocrural and posterior STJ in their involved limbs relative to the contralateral and a healthy control limb. Cartilage composition findings may be consistent with the early development of posttraumatic osteoarthritis

Trends in movement quality in US Military Academy cadets 2005-17: A JUMP-ACL study

Objectives: This study sought to determine if there were significant trends in lower extremity movement quality, as assessed by the Landing Error Scoring System (LESS) scores and plane-specific LESS subscales, across in 12 recent cohorts of incoming USMA cadets. Design: prospective cohort study. Setting: United States Military Academy. Participants: 7,591. Main outcome measures: Landing Error Scoring System (LESS) scores, adjusted for sex and ACL injury history. Results: Statistically significant inverse trends were found between total LESS score and year (p < 0.01) and sagittal plane subscale and year (p < 0.01). A statistically significant direct trend was found for the frontal/transverse plane subscale and year (p < 0.01). However, each of these trends had a small associated effect size, and none were considered clinically meaningful. Conclusions: There were no meaningful changes in lower extremity movement quality in incoming US Military Academy cadets between 2005 and 2017

Lower Extremity Musculoskeletal Injury in US Military Academy Cadet Basic Training: A Survival Analysis Evaluating Sex, History of Injury, and Body Mass Index

Background: Injury incidence for physically active populations with a high volume of physical load can exceed 79%. There is little existing research focused on timing of injury and how that timing differs based on certain risk factors. Purpose/Hypothesis: The purpose of this study was to report both the incidence and timing of lower extremity injuries during cadet basic training. We hypothesized that women, those with a history of injury, and those in underweight and obese body mass index (BMI) categories would sustain lower extremity musculoskeletal injury earlier in the training period than men, those without injury history, and those in the normal-weight BMI category. Study Design: Cohort study; Level of evidence, 2. Methods: Cadets from the class of 2022, arriving in 2018, served as the study population. Baseline information on sex and injury history was collected via questionnaire, and BMI was calculated from height and weight taken during week 1 at the United States Military Academy. Categories were underweight (BMI <20), middleweight (20-29.99), and obese (≥30). Injury surveillance was performed over the first 60 days of training via electronic medical record review and monitoring. Kaplan-Meier survival curves were used to estimate group differences in time to the first musculoskeletal injury. Cox proportional hazard regression was used to estimate hazard ratios (HRs). Results: A total of 595 cadets participated. The cohort was 76.8% male, with 29.9% reporting previous injury history and 93.3% having a BMI between 20 and 30. Overall, 16.3% of cadets (12.3% of male cadets and 29.7% of female cadets) experienced an injury during the follow-up period. Women experienced significantly greater incident injury than did men (P <.001). Separation of survival curves comparing the sexes and injury history occurred at weeks 3 and 4, respectively. Hazards for first musculoskeletal injury were significantly greater for women versus men (HR, 2.63; 95% CI, 1.76-3.94) and for those who reported a history of injury versus no injury history (HR, 1.76; 95% CI, 1.18-2.64). No differences were observed between BMI categories. Conclusion: Female cadets and those reporting previous musculoskeletal injury demonstrated a greater hazard of musculoskeletal injury during cadet basic training. This study did not observe an association between BMI and injury

Ankle Sprains in the National Basketball Association, 2013-2014 Through 2016-2017

Background: Ankle sprains are one of the most common injuries in basketball. Despite this, the incidence and setting of ankle sprains among elite basketball players are not well described. Purpose: To describe the epidemiology of ankle sprains among National Basketball Association (NBA) players. Study Design: Cohort study; Level of evidence, 3. Methods: All players on an NBA roster for ≥1 NBA game (preseason, regular season, or playoffs) during the 2013-14 through 2016-17 seasons were included. Data were collected with the NBA electronic medical record system. All NBA teams used the electronic medical record continuously throughout the study period to record comprehensive injury data, including onset, mechanism, setting, type, and time lost. Game incidence rates were calculated per 1000 player-games and per 10,000 player-minutes of participation, stratified by demographic and playing characteristics. Results: There were 796 ankle sprains among 389 players and 2341 unique NBA player-seasons reported in the league from 2013-14 through 2016-17. The overall single-season risk of ankle sprain was 25.8% (95% CI, 23.9%-28.0%). The majority of ankle sprains occurred in games (n = 565, 71.0%) and involved a contact mechanism of injury (n = 567, 71.2%). Most ankle sprains were lateral (n = 638, 80.2%). The incidence of ankle sprain among players with a history of prior ankle sprain in the past year was 1.41 times (95% CI, 1.13-1.74) the incidence of those without a history of ankle sprain in the past year (P =.002). Fifty-six percent of ankle sprains did not result in any NBA games missed (n = 443); among those that did, players missed a median of 2 games (interquartile range, 1-4) resulting in a cumulative total of 1467 missed player-games over the 4-season study period. Conclusion: Ankle sprains affect approximately 26% of NBA players on average each season and account for a large number of missed NBA games in aggregate. Younger players and players with a history of ankle sprain have elevated rates of incident ankle sprains in games, highlighting the potential benefit for integrating injury prevention programs into the management of initial sprains. Research on basketball- and ankle-specific injury prevention strategies could provide benefits

Annihilation vs. Decay: Constraining dark matter properties from a gamma-ray detection

Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models.Comment: 29 pp, 8 figs; replaced to match published version (minor changes and some new references