Cook, Rio, Purdam & Docking (2016) 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.

Rio, van Ark, Docking, Moseley, Kidgell, Gaida, van den Akker-Scheek, Zwerver & Cook (2017) Isometric contractions Are more analgesic than isotonic contractions for patellar tendon pain: an in-season randomized clinical trial. 

Objective This study aimed to compare the immediate analgesic effects of 2 resistance programs in in-seasonathletes with patellar tendinopathy (PT). Resistance training is noninvasive, a principle stimulus for corticospinal and neuromuscular adaptation, and may be analgesic.
Design Within-season randomized clinical trial. Data analysis was conducted blinded to group.
Setting Subelite volleyball and basketball competitions.
Participants Twenty jumping athletes aged more than 16 years, participating in games/trainings 3 times per week with clinically diagnosed PT.
Interventions Two quadriceps resistance protocols were compared; (1) isometric leg extension holds at 60 degrees knee flexion (80% of their maximal voluntary isometric contraction) or (2) isotonic leg extension (at 80% of their 8 repetition maximum) 4 times per week for 4 weeks. Time under load and rest between sets was matched between groups.
Main Outcome Measures (1) Pain (0-10 numerical rating score) during single leg decline squat (SLDS), measured preintervention and postintervention sessions. (2) VISA-P, a questionnaire about tendon pain and function, completed at baseline and after 4 weeks.
Results Twenty athletes with PT (18 men, mean 22.5 ± 4.7 years) participated (isotonic n = 10, isometric n = 10). Baseline median SLDS pain was 5/10 for both groups (isotonic range 1-8, isometric range 2-8). Isometriccontractions produced significantly greater immediate analgesia (P < 0.002). Week one analgesic response positively correlated with improvements in VISA-P at 4 weeks (r2 = 0.64).
Conclusions Both protocols appear efficacious for in-season athletes to reduce pain, however, isometriccontractions demonstrated significantly greater immediate analgesia throughout the 4-week trial. Greater analgesia may increase the ability to load or perform.

van Ark, Cook, Docking, Zwerver, Gaida, van den Akker-Scheek, Rio (2016) Do isometric and isotonic exercise programs reduce pain in athletes with patellar tendinopathy in-season? A randomised clinical trial.

Objectives Many athletes with patellar tendinopathy participate in sports with symptoms during or after activities. Current treatments do not decrease pain in-season; eccentric exercises in-season result in an increase in pain. This study examined if isometric and isotonic exercises relieved pain in competing athletes with patellar tendinopathy.
Design Randomised clinical trial.
Methods Jumping athletes with patellar tendinopathy playing at least three times per week participated in this study. Athletes were randomised into an isometric or isotonic exercise group. The exercise programs consisted of four isometric or isotonic exercise sessions per week for four weeks. Pain during a single leg decline squat (SLDS) on a Numeric Rating Scale (NRS; 0–10) was used as the main outcome measure; measurements were completed at baseline and at 4-week follow-up.
Results Twenty-nine athletes were included in this study. Median pain scores improved significantly over the 4-week intervention period in both the isometric group (Z = −2.527, p = 0.012, r = −0.63) and isotonic group (Z = −2.952, p = 0.003, r = −0.63). There was no significant difference in NRS pain score change (U = 29.0, p = 0.208, r = 0.29) between the isometric group (median (IQR), 2.5 (1–4.5)) and isotonic group (median (IQR), 3.0 (2–6)).
Conclusions This is the first study to show a decrease in patellar tendon pain without a modification of training and competition load and the first study to investigate isometric exercises in a clinical setting. Both isometric and isotonic exercise programs are easy-to-use exercises that can reduce pain from patellar tendinopathy for athletes in-season.

Drew, Smith, Littlewood & Sturrock (2014) Do structural changes (eg, collagen/matrix) explain the response to therapeutic exercises in tendinopathy: a systematic review.

Background Previous reviews have highlighted the benefit of loaded therapeutic exercise in the treatment of tendinopathy. Changes in observable structural outcomes have been suggested as a possible explanation for this response to therapeutic exercise. However, the mechanism for the efficacy of therapeutic exercise remains unclear.
Objective To systematically review the relationship between the observable structural change and clinical outcomes following therapeutic exercise.
Data sources An electronic search of AMED, CiNAHL, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PEDro and SPORTDiscus was undertaken from their inception to June 2012.
Study eligibility criteria Any study design that incorporated observable structural outcomes and clinical outcomes when assessing the effect of therapeutic exercise on participants with tendinopathy.
Study appraisal and synthesis methods Included studies were appraised for risk of bias using the tool developed by the Cochrane Back Review Group. Due to heterogeneity of studies, a qualitative synthesis was undertaken.
Results Twenty articles describing 625 patients were included. Overall, there is a strong evidence to refute any observable structural change as an explanation for the response to therapeutic exercise when treated by eccentric exercise training. Moderate evidence does exist to support the response of heavy-slow resistance training (HSR).
Conclusions and implications of key findings The available literature does not support observable structural change as an explanation for the response of therapeutic exercise except for some support from HSR. Future research should focus on indentifying other explanations including neural, biochemical and myogenic changes.

Tristan Chai