Johannes Zwerver

Prevalence of Jumper’s Knee Among Nonelite Athletes From Different Sports A Cross-Sectional Survey

Background: The prevalence of jumper’s knee among nonelite athletes from different sports is unknown. Purpose: This study was undertaken to determine the prevalence of jumper’s knee in nonelite athletes from different sports and to determine potential risk factors for jumper’s knee. Design: Cohort study (prevalence); Level of evidence, 2. Methods: The authors interviewed 891 male and female nonelite athletes from 7 popular sports in The Netherlands: basketball, volleyball, handball, korfball, soccer, field hockey, and track and field. Using a specially developed questionnaire, information was obtained about individual characteristics (age, height, and weight), training background, previous and actual knee problems, and the VISA-P (Victorian Institute of Sport Assessment–Patella) score. Results: The overall prevalence of current jumper’s knee was 8.5% (78 of 891 athletes), showing a significant difference between sports with different loading characteristics. Prevalence was highest among volleyball players (14.4%) and lowest among soccer players (2.5%); it was significantly higher among male athletes (51 of 502 [10.2%]) than female athletes (25 of 389 [6.4%]) (χ2 = 3.91, P = .048). The mean duration of symptoms was 18.9 months (standard deviation [SD], 21.6; median value, 12.0; range, 2.0-59.8). The mean VISA-P score of the athletes with jumper’s knee was 71.4 (SD, 13.8). Athletes with jumper’s knee were significantly younger, taller, and heavier than those without jumper’s knee. Conclusion: Prevalence of jumper’s knee is high among nonelite athletes and varies between 14.4% and 2.5% for different sports. Jumper’s knee is almost twice as common among male nonelite athletes compared with female athletes. Different sport-specific loading characteristics of the knee extensor apparatus, a younger age, a taller body stature, and higher body weight seem to be risk factors associated with patellar tendinopathy.

Monitoring stress and recovery: new insights for the prevention of injuries and illnesses in elite youth soccer players

Objective Elite youth soccer players have a relatively high risk for injuries and illnesses due to increased physical and psychosocial stress. The aim of this study is to investigate how measures to monitor stress and recovery, and its analysis, provide useful information for the prevention of injuries and illnesses in elite youth soccer players. Methods 53 elite soccer players between 15 and 18 years of age participated in this study. To determine physical stress, soccer players registered training and match duration and session rating of perceived exertion for two competitive seasons by means of daily training logs. The Dutch version of the Recovery Stress Questionnaire for athletes (RESTQ-Sport) was administered monthly to assess the psychosocial stress–recovery state of players. The medical staff collected injury and illness data using the standardised Fédération Internationale de Football Association registration system. ORs and 95% CIs were calculated for injuries and illnesses using multinomial regression analyses. The independent measures were stress and recovery. Results During the study period, 320 injuries and 82 illnesses occurred. Multinomial regression demonstrated that physical stress was related to both injury and illness (range OR 1.01 to 2.59). Psychosocial stress and recovery were related the occurrence of illness (range OR 0.56 to 2.27). Conclusions Injuries are related to physical stress. Physical stress and psychosocial stress and recovery are important in relation to illness. Individual monitoring of stress and recovery may provide useful information to prevent soccer players from injuries and illnesses.

Extracorporeal shockwave therapy for patellar tendinopathy: a review of the literature

Background and purpose: Extracorporeal shockwave therapy (EWST) has become a popular treatment for patellar tendinopathy. The purpose of this review was to study the effectiveness of ESWT treatment for patellar tendinopathy; to draft guidelines for an effective treatment protocol of ESWT treatment; and to identify topics for further research. Methods: A computerised search of the Medline and Embase databases was conducted on 1 August 2007, to identify studies dealing with the effectiveness of ESWT for patellar tendinopathy. Results: Seven articles describing the effectiveness of ESWT on patellar tendinopathy, all published after 2000, were included. These studies included a total of 283 patients (298 tendons), 204 of whom (215 tendons) were assigned to ESWT treatment. The treatment results were positive but most studies had methodological deficiencies, small numbers and/or short follow-up periods. Method of application and shockwave generation, energy level, number and frequency of treatments, use of (local) anaesthesia and method of localisation were variable. Conclusion: ESWT seems to be a safe and promising treatment for patellar tendinopathy with a positive effect on pain and function. Based on current knowledge it is impossible to recommend a specific treatment protocol. Further basic and clinical research into the working mechanism and effectiveness of ESWT for patellar tendinopathy are necessary.

Risk factors for patellar tendinopathy: a systematic review of the literature

Patellar tendinopathy (PT) is an injury with a high prevalence in sports. Knowledge of risk factors is essential for developing preventive measures and rehabilitation programmes. However, risk factors associated with PT have not yet been systematically studied. This review was undertaken to identify risk factors associated with PT. The literature was systematically searched to identify articles that investigated risk factors for PT. There was no strong or moderate evidence that any investigated risk factor was associated with PT. For nine risk factors there was some evidence: weight, body mass index, waist-to-hip ratio, leg-length difference, arch height of the foot, quadriceps flexibility, hamstring flexibility, quadriceps strength and vertical jump performance. Based on the present evidence, reducing body weight, increasing upper-leg flexibility and quadriceps strength and the use of orthotics may be beneficial treatment options. However, it should be stressed that the evidence for the nine identified risk factors was only limited. Therefore, there is a clear need for high-quality studies in order to identify the exact risk factors associated with PT.

Sports and exercise-related tendinopathies: A review of selected topical issues by participants of the second International Scientific Tendinopathy Symposium (ISTS) Vancouver 2012

In September 2010, the first International Scientific Tendinopathy Symposium (ISTS) was held in Umeå, Sweden, to establish a forum for original scientific and clinical insights in this growing field of clinical research and practice. The second ISTS was organised by the same group and held in Vancouver, Canada, in September 2012. This symposium was preceded by a round-table meeting in which the participants engaged in focused discussions, resulting in the following overview of tendinopathy clinical and research issues. This paper is a narrative review and summary developed during and after the second ISTS. The document is designed to highlight some key issues raised at ISTS 2012, and to integrate them into a shared conceptual framework. It should be considered an update and a signposting document rather than a comprehensive review. The document is developed for use by physiotherapists, physicians, athletic trainers, massage therapists and other health professionals as well as team coaches and strength/conditioning managers involved in care of sportspeople or workers with tendinopathy.

Relationship between landing strategy and patellar tendinopathy in volleyball

Objective: The aetiology of patellar tendinopathy (jumper’s knee) remains unclear. To see whether landing strategy might be a risk factor for the development of this injury, this study examined whether landing dynamics from drop jumps differed among healthy volleyball players (CON) and volleyball players with a jumper’s knee. The patients with jumper’s knee were divided into an asymptomatic group with a previous jumper’s knee (PJK) and a symptomatic group with a recent jumper’s knee (RJK). Methods: Inverse dynamics analyses were used to estimate lower extremity joint dynamics from 30, 50 and 70 cm drop jumps in the three groups (CON, n = 8; PJK, n = 7; RJK, n = 9). A univariate repeated measures analysis of variance was used to compare the different landing techniques. Results: Data analysis of the landing dynamics revealed that PJK showed higher knee angular velocities (p<0.01), and higher ankle plantar flexion moment loading rate (p<0.01). Furthermore, strong tendencies of higher loading rate of vertical ground reaction force (p = 0.05) and higher knee extensor moment loading rate (p = 0.08) were found compared with CON. Higher values for peak knee moment, peak knee power and knee work (all p<0.01) were found for CON compared with RJK. The comparison of the two jumper’s knee groups yielded higher knee angular velocities (p<0.01), together with higher ankle plantar flexion and knee extensor moment loading rate (p<0.01 and p<0.05, respectively). Conclusion: Where RJK used a landing technique to avoid high patellar tendon loading, PJK used a stiffer landing strategy, which may be a risk factor in the development of patellar tendinopathy.

No Effect of Extracorporeal Shockwave Therapy on Patellar Tendinopathy in Jumping Athletes During the Competitive Season: A Randomized Clinical Trial

Background: Patellar tendinopathy is a common overuse injury among jumping athletes. No evidence-based treatment guidelines exist. Extracorporeal shockwave therapy (ESWT) appears to be a promising treatment but its effectiveness has not been studied in athletes with patellar tendinopathy who have symptoms for 3 to 12 months and are still playing. Purpose: The TOPGAME study was created to determine the effectiveness of ESWT on pain, symptoms, and function in athletes with early symptomatic patellar tendinopathy who are still in training and competition. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Athletes playing volleyball, basketball, or handball with patellar tendinopathy for 3 to 12 months were randomized into the ESWT or placebo group during the first half of the season. The ESWT group received 3 ESWT treatments while the placebo group received sham ESWT. In-season follow-up measurements were 1, 12, and 22 weeks after treatment. The primary outcome was severity of patellar tendinopathy determined with the Victorian Institute of Sport Assessment–Patella (VISA-P) questionnaire. Secondary outcome measures were pain during activities of daily living and sports and after functional knee-loading tests rated on a visual analog scale and subjective improvement. Multilevel analyses were performed to determine differences between groups over time. Results: Of the 127 symptomatic athletes invited to participate, 62 were eligible, gave consent, and were randomized into the ESWT (n = 31) or placebo group (n = 31). Mean VISA-P scores before and 1, 12, and 22 weeks after treatment were 59.4 (±11.7), 66.8 (±16.2), 66.7 (±17.5), and 70.5 (±18.9) for the ESWT group and 62.4 (±13.4), 66.3 (±19.0), 68.9 (±20.3), and 72.7 (±18.0) for the placebo group. For the VISA-P, there was a significant effect for time (P < .01) but no treatment × time interaction effect (P = .82). The same pattern was seen in visual analog scale pain scores. One week after final treatment, significantly more athletes in the ESWT group reported subjective improvement (65% vs 32%; χ2 = 6.46, P = .01). This was the only difference noted between the 2 groups. Conclusion: Extracorporeal shockwave therapy as a solitary treatment during the competitive season has no benefit over placebo treatment in the management of actively competing jumping athletes with patellar tendinopathy who have symptoms for less than 12 months.

Biomechanical analysis of the single-leg decline squat

Background: The single-leg squat on a 25° decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. Several assumptions have been made about its working mechanism on patellar load and patellofemoral forces, but these are not substantiated by biomechanical evaluations. Aim: To investigate knee moment and patellofemoral contact force as a function of decline angle in the single-leg squat. Methods: Five subjects performed single-leg eccentric squats at decline angles of 0°, 5°, 10°, 15°, 20° and 25° (with/without a backpack of 10 kg), and 30° on a board that was placed over a forceplate. Kinematic and forceplate data were recorded by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics. Results: Knee moment increased by 40% at decline angles of 15° and higher, whereas hip and ankle moment decreased. Maximum knee and ankle angles increased with steeper decline. With a 10 kg backpack at 25° decline, the knee moment was 23% higher than unloaded. Both patellar tendon and patellofemoral forces increased with higher decline angles, but beyond 60°, the patellofemoral force rose steeper than the tendon force. Conclusions: All single-leg squats at decline angles >15° result in 40% increase in maximum patellar tendon force. In knee flexions >60°, patellofemoral forces increase more than patellar tendon forces. Higher tendon load can be achieved by the use of a backpack with extra weight.

ESWT for tendinopathy: Technology and clinical implications

PurposeThe general consensus that tendinopathy, at least in the chronic stage, is mainly a degenerative condition and inflammation plays a minor role has led to a shift from treatments that target inflammation towards treatment options that promote regeneration. One of these treatments is extracorporeal shockwave therapy (ESWT), a physical therapy modality that uses pressure waves to treat tendinopathy. This review was undertaken to give an overview of the literature concerning this treatment, and special attention is given to the differences between focused and radial ESWT.MethodsA narrative description of wave characteristics, generation methods and in vitro effects of ESWT is given. The literature on ESWT as a treatment for one common tendinopathy, patellar tendinopathy, was systematically reviewed.ResultsWaves that are generated for focused and radial ESWT have very different physical characteristics. It is unclear how these characteristics are related to clinical effectiveness. Studies into the biological effects of ESWT have mainly used focused shockwave therapy, showing a number of effects of shockwaves on biological tissue. The systematic review of studies into the clinical effects of ESWT for patellar tendinopathy showed conflicting evidence for its effectiveness.ConclusionPhysical characteristics of focused and radial waves differ substantially, but effect on clinical effectiveness is unclear. Whereas in vitro studies often show the effects of ESWT on tendon tissue, results of clinical studies are inconsistent. Based on the review of the literature, suggestions are given for the use of ESWT in clinical practice regarding timing and treatment parameters.Level of evidenceIV.

Injection treatments for patellar tendinopathy

Objective Injection treatments are increasingly used as treatment for patellar tendinopathy. The aim of this systematic review is to describe the different injection treatments, their rationales and the effectiveness of treating patellar tendinopathy. Methods A computerised search of the Medline, Embase, CINAHL and Web of Knowledge databases was conducted on 1 May 2010 to identify studies on injection treatments for patellar tendinopathy. Results 11 articles on seven different injection treatments (dry needling, autologous blood, high-volume, platelet-rich plasma, sclerosis, steroids and aprotinin injections) were found: 4 randomised controlled trials (RCTs), 1 non-RCT, 4 prospective cohort studies and 2 retrospective cohort studies. All studies reported positive results. The Delphi scores of the four RCTs ranged from 5 to 8 out of 9. Different and sometimes contradictory rationales were used for the injection treatments. Conclusion All seven different injection treatments seem promising for treating patellar tendinopathy. Unlike the other injection treatments, steroid treatment often shows a relapse of symptoms in the long term. Results should be interpreted with caution as the number of studies is low, few high-quality studies have been conducted and the studies are hard to compare due to different methodology. More high-quality studies using the same cross-cultural reliable and valid outcome measure are needed, as well as further research into the pathophysiology. Finally, some implications are provided for clinicians who want to use injection treatments as a part of their treatment for patellar tendinopathy, distinguishing between reactive and degenerative phase of patellar tendinopathy.