Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?

The pathogenesis of tendinopathy and the primary biological change in the tendon that precipitates pathology have generated several pathoaetiological models in the literature. The continuum model of tendon pathology, proposed in 2009, synthesised clinical and laboratory-based research to guide treatment choices for the clinical presentations of tendinopathy. While the continuum has been cited extensively in the literature, its clinical utility has yet to be fully elucidated. The continuum model proposed a model for staging tendinopathy based on the changes and distribution of disorganisation within the tendon. However, classifying tendinopathy based on structure in what is primarily a pain condition has been challenged. The interplay between structure, pain and function is not yet fully understood, which has partly contributed to the complex clinical picture of tendinopathy. Here we revisit and assess the merit of the continuum model in the context of new evidence. We (1) summarise new evidence in tendinopathy research in the context of the continuum, (2) discuss tendon pain and the relevance of a model based on structure and (3) describe relevant clinical elements (pain, function and structure) to begin to build a better understanding of the condition. Our goal is that the continuum model may help guide targeted treatments and improved patient outcomes.

The challenge of managing tendinopathy in competing athletes.

Managing tendinopathy in season is a challenge for all sports medicine practitioners. Many of the strategies employed to treat tendinopathy in a rehabilitation setting are not suitable because of the time taken to recover. Management strategies that control pain and maintain performance are required. These include load management, both reducing aggravating loads and introducing pain-relieving loads, medications and adequate monitoring to detect a deteriorating tendon. Other interventions such as intratendinous injection therapies and other direct tendon modalities can be provocative at worst and without effect at best. Research to improve the understanding of management in athletes in season is compromised by ethical considerations and access to willing participants. It is likely to remain an area where clinical advances guide future treatments.

Characterizing patellar tendon loading during the landing phases of a stop-jump task.

Excessive extensor mechanism loading from repeated landing has been associated with overuse knee injuries, especially patellar tendinopathy. In order to reduce these loads, it is important to establish which landing task places the highest load on the patellar tendon. It was hypothesized that the horizontal landing would create higher patellar tendon force (F(PT)) compared with the vertical landing. Sixteen male athletes with healthy patellar tendons performed five successful trials of a stop-jump task, which involved a symmetrical two-foot landing after a horizontal approach (horizontal landing) followed by another symmetrical two-foot landing after a vertical jump (vertical landing). For both lower limbs during each trial, the participants' ground reaction forces were recorded, three-dimensional kinematics measured and F(PT) calculated by dividing the net knee joint moment by the patellar tendon moment arm. Compared with the vertical landing, significantly higher F(PT), posterior ground reaction forces and F(PT) loading rates were generated during the horizontal landing, despite lower vertical ground reaction forces (F(V)), highlighting the notion that F(V) should not be used to reflect F(PT). Understanding that a horizontal landing task places the highest load on the patellar tendon, provides an appropriate framework for future research to investigate lower limb landing strategies in athletes with patellar tendinopathy.

Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy.

Overuse tendinopathy is problematic to manage clinically. People of different ages with tendons under diverse loads present with varying degrees of pain, irritability, and capacity to function. Recovery is similarly variable; some tendons recover with simple interventions, some remain resistant to all treatments. The pathology of tendinopathy has been described as degenerative or failed healing. Neither of these descriptions fully explains the heterogeneity of presentation. This review proposes, and provides evidence for, a continuum of pathology. This model of pathology allows rational placement of treatments along the continuum. A new model of tendinopathy and thoughtful treatment implementation may improve outcomes for those with tendinopathy. This model is presented for evaluation by clinicians and researchers.

Low-intensity pulsed ultrasound for chronic patellar tendinopathy: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: Patellar tendinopathy (PT) is a common and significant clinical condition for which there are few established interventions. One intervention that is currently being used clinically to manage PT symptoms is the introduction of low-intensity pulsed ultrasound (LIPUS). The aim of this study was to investigate the clinical efficacy of LIPUS in the management of PT symptoms. METHODS: A randomized, double-blind, placebo-controlled study was conducted. Volunteers with clinically and radiologically confirmed PT were randomly allocated to either an active-LIPUS (treatment) or inactive-LIPUS (placebo) group. LIPUS was self-administered by participants for 20 min/day, 7 days/week for 12 weeks. All participants also completed a daily, standardized eccentric exercise programme based on best practice. Primary outcomes were change in pain during the participant's most aggravating activity in the preceding week, measured on 10 cm visual analogue scales for both usual (VAS-U) and worst (VAS-W) tendon pain. RESULTS: Out of 156 individuals who volunteered, 37 met the eligibility criteria and were randomized to either active-LIPUS (n = 17) or inactive-LIPUS (n = 20). Using an intention-to-treat analysis, VAS-U and VAS-W for the entire cohort decreased by 1.6 +/- 1.9 cm (P < 0.01) and 2.5 +/- 2.4 cm (P < 0.01), respectively. There were no differences between the active- and inactive-LIPUS groups for change in VAS-U (-0.2 cm; 95% CI, -1.5, 1.1 cm) (P = 0.74) or VAS-W (-0.5 cm; 95% CI, -2.1, 1.1 cm) (P = 0.57). A per-protocol analysis provided similar results. CONCLUSIONS: These findings suggest that LIPUS does not provide any additional benefit over and above placebo in the management of symptoms associated with PT.

Eccentric decline squat protocol offers superior results at 12 months compared with traditional eccentric protocol for patellar tendinopathy in volleyball players.

BACKGROUND: Conservative treatment of patellar tendinopathy has been minimally investigated. Effective validated treatment protocols are required. OBJECTIVES: To investigate the immediate (12 weeks) and long term (12 months) efficacy of two eccentric exercise programmes for the treatment of patellar tendinopathy. METHODS: This was a prospective randomised controlled trial of 17 elite volleyball players with clinically diagnosed and imaging confirmed patellar tendinopathy. Participants were randomly assigned to one of two treatment groups: a decline group and a step group. The decline group were required to perform single leg squats on a 25 degrees decline board, exercising into tendon pain and progressing their exercises with load. The step group performed single leg squats on a 10 cm step, exercising without tendon pain and progressing their exercises with speed then load. All participants completed a 12 week intervention programme during their preseason. Outcome measures used were the Victorian Institute of Sport Assessment (VISA) score for knee function and 100 mm visual analogue scale (VAS) for tendon pain with activity. Measures were taken throughout the intervention period and at 12 months. RESULTS: Both groups had improved significantly from baseline at 12 weeks and 12 months. Analysis of the likelihood of a 20 point improvement in VISA score at 12 months revealed a greater likelihood of clinical improvements in the decline group than the step group. VAS scores at 12 months did not differ between the groups. CONCLUSIONS: Both exercise protocols improved pain and sporting function in volleyball players over 12 months. This study indicates that the decline squat protocol offers greater clinical gains during a rehabilitation programme for patellar tendinopathy in athletes who continue to train and play with pain.

A pilot study of the eccentric decline squat in the management of painful chronic patellar tendinopathy.

OBJECTIVES: This non-randomised pilot study investigated the effect of eccentric quadriceps training on 17 patients (22 tendons) with painful chronic patellar tendinopathy. METHODS: Two different eccentric exercise regimens were used by subjects with a long duration of pain with activity (more than six months). (a) Nine consecutive patients (10 tendons; eight men, one woman; mean age 22 years) performed eccentric exercise with the ankle joint in a standard (foot flat) position. (b) Eight patients (12 tendons; five men, three women; mean age 28 years) performed eccentric training standing on a 25 degrees decline board, designed to increase load on the knee extensor mechanism. The eccentric training was performed twice daily, with three sets of 15 repetitions, for 12 weeks. Primary outcome measures were (a) 100 mm visual analogue scale (VAS), where the subject recorded the amount of pain during activity, and (b) return to previous activity. Follow up was at 12 weeks, with a further limited follow up at 15 months. RESULTS: Good clinical results were obtained in the group who trained on the decline board, with six patients (nine tendons) returning to sport and showing a significantly reduced amount of pain over the 12 week period. Mean VAS scores fell from 74.2 to 28.5 (p = 0.004). At 15 months, four patients (five tendons) reported satisfactory results (mean VAS 26.2). In the standard squat group the results were poor, with only one athlete returning to previous activity. Mean VAS scores in this group were 79.0 at baseline and 72.3 at 12 weeks (p = 0.144). CONCLUSION: In a small group of patients with patellar tendinopathy, eccentric squats on a decline board produced encouraging results in terms of pain reduction and return to function in the short term. Eccentric exercise using standard single leg squats in a similar sized group appeared to be a less effective form of rehabilitation in reducing pain and returning subjects to previous levels of activity.

Reproducibility and clinical utility of tendon palpation to detect patellar tendinopathy in young basketball players. Victorian Institute of Sport tendon study group.

BACKGROUND: Palpation is an important clinical test for jumper's knee. OBJECTIVES: To (a) test the reproducibility of palpation tenderness, (b) evaluate the sensitivity and specificity of palpation in subjects with clinical symptoms of jumper's knee, and (c) determine whether tenderness to palpation may serve as a useful screening test for patellar tendinopathy. The yardstick for diagnosis of patellar tendinopathy was ultrasonographic abnormality. METHODS: In 326 junior symptomatic and asymptomatic athletes' tendons, palpation was performed by a single examiner before ultrasonographic examination by a certified ultrasound radiologist. In 58 tendons, palpation was performed twice to test reliability. Tenderness to palpation was scored on a scale from 0 to 3 where 0 represented no pain, and 1, 2, and 3 represented mild, moderate, and severe tenderness respectively. RESULTS: Patellar tendon palpation was a reliable examination for a single examiner (Pearson r = 0.82). In symptomatic tendons, the positive predictive value of palpation was 68%. As a screening examination in asymptomatic subjects, the positive predictive value of tendon palpation was 36-38%. Moderate and severe palpation tenderness were better predictors of ultrasonographic tendon pathology than absent or mild tenderness (p<0.001). Tender and symptomatic tendons were more likely to have ultrasound abnormality than tenderness alone (p<0.01). CONCLUSIONS: In this age group, palpation is a reliable test but it is not cost effective in detecting patellar tendinopathy in a preparticipation examination. In symptomatic tendons, palpation is a moderately sensitive but not specific test. Mild tenderness in the patellar tendons in asymptomatic jumping athletes should be considered normal.

Prospective imaging study of asymptomatic patellar tendinopathy in elite junior basketball players.

To evaluate the ability of ultrasonography to predict eventual symptoms in an at-risk population, 52 elite junior basketball players' patellar tendons were studied at baseline and again 16 months later. The group consisted of 10 study tendons (ultrasonographically hypoechoic at baseline) and 42 control tendons (ultrasonographically normal at baseline). By design, all tendons were asymptomatic at baseline. No differences were noted between subjects and controls at baseline for age, height, weight, training hours, and vertical jump. Functional (P < 0.01) and symptomatic outcome (P < 0.05) were poorer for subjects' tendons than for controls. Relative risk for developing symptoms of jumper's knee was 4.2 times greater in case tendons than in control tendons. Men were more likely to develop ultrasonographic changes than women (P < 0.025), and they also had significantly increased training hours per week (P < 0.01) in the study period. Half (50%) of abnormal tendons in women became ultrasonographically normal in the study period. Our data suggest that presence of an ultrasonographic hypoechoic area is associated with a greater risk of developing jumper's knee symptoms. Ultrasonographic patellar tendon changes may resolve, but this is not necessary for an athlete to become asymptomatic. Qualitative or quantitative analysis of baseline ultrasonographic images revealed it was not possible to predict which tendons would develop symptoms or resolve ultrasonographically.

Anthropometry, physical performance, and ultrasound patellar tendon abnormality in elite junior basketball players: a cross-sectional study.

OBJECTIVE: Patellar tendinopathy has been reported to be associated with many intrinsic risk factors. Few have been fully investigated. This cross-sectional study examined the anthropometric and physical performance results of elite junior basketball players with normal or abnormal patellar tendons to see if any measures were associated with changes in tendon morphology. METHODS: Agility, leg strength, endurance, and flexibility were measured in 71 male and 64 female players. A blinded radiologist ultrasonographically examined their patellar tendons and athletes were grouped as having normal or abnormal tendons. One-way ANOVA was used to test for differences in anthropometric and physical performance data for athletes whose tendons were normal or abnormal (unilateral or bilateral tendinopathy) on ultrasound. RESULTS: Results show that females with abnormalities in their tendons had a significantly better vertical jump (50.9+/-6.8 cm) than those with normal tendons (46.1+/-5.4 cm) (p = 0.02). This was not found in males. In males, the mean sit and reach in those with normal tendons (13.2+/-6.7 cm) was greater (p<0.03) than in unilateral tendinopathy (10.3+/-6.2 cm) or in bilateral tendinopathy (7.8+/-8.3 cm). In females, those with normal tendons (13.3+/-4.8 cm) and bilateral tendinopathy (15.8+/-6.2 cm) were distinctly different from those with unilateral tendinopathy (7.9+/-6.6 cm). CONCLUSION: Flexibility and vertical jump ability are associated with patellar tendinopathy and the findings warrant consideration when managing young, jumping athletes.