Ultrasound-guided tendon debridement improves pain, function and structure in persistent patellar tendinopathy: Short term follow-up of a case series

Abstract

There is a need for effective therapeutic options for resistant patellar tendinopathy. Ultrasound (US)-guided arthroscopic debridement has demonstrated promising clinical results.

Objectives
To prospectively evaluate pain, function, tendon structure and adverse events after US and colour Doppler (CD)-guided arthroscopic debridement for persistent painful patellar tendinopathy.

Materials and methods
Twenty-three consecutive patients (19 males and 4 females, mean age 28 years (±8), symptom duration 25 months (±21)), who had failed conservative management including progressive loading, were included. US+CD and ultrasound tissue characterisation (UTC) examination verified the clinical diagnosis and quantified baseline tendon structure. Patients were treated with US+CD-guided arthroscopic debridement followed by a specific rehabilitation protocol. Outcomes were VISA-P score for pain and function and UTC for tendon structure. Adverse events were specifically elicited.

Results
At 6-month follow-up, mean VISA-P score increased from 40 (±21.0) to 82 (±15) (mean deviation (MD)=42.0, 95% CI 32 to 53, d =2.4), while organised echo pixels (combined UTC type I+II) increased from 55.0% (±17.0) to 69.0% (±15.0) (MD=14.0, d =0.7, 95% CI 2 to 21). Both outcomes exceeded minimum detectable change values. Twenty-one participants returned to their prediagnosis activity levels, and there were no significant adverse events.

Conclusions
US-guided patellar tendon debridement for persistent patellar tendinopathy improved symptoms and tendon structure without complications at 6-month follow-up. A majority (21/23) of the patients returned to their preinjury activity level. Further studies with longer follow-ups, preferably randomised and controlled, are needed.

Full text

MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803 1
Open access Short report
Ultrasound- guided tendon debridement
improves pain, function and structure in
persistent patellar tendinopathy: short
term follow- up of a case series
Lorenzo Masci ,1,2 Hakan Alfredson,3,4 Brad Neal,1 William Wynter Bee2
To cite: MasciL, AlfredsonH,
NealB, etal. Ultrasound-
guided tendon debridement
improves pain, function and
structure in persistent patellar
tendinopathy: short term follow-
up of a case series. BMJ Open
Sport & Exercise Medicine
2020;6:e000803. doi:10.1136/
bmjsem-2020-000803
Accepted 23 June 2020
1Department of Sports and
Execise Medicine, Queen Mary
University of London, London, UK
2Department of Sports and
Exerciee Medicine, ISEH,
London, UK
3Department of Community
Medicine and Rehabilitation,
Sports Medicine, Umeå
University, Umea, Sweden
4Clinical Research, Pure Sports
Medicine, London, UK
Correspondence to
Dr Lorenzo Masci;
lorenzo@ sportdoctorlondon. com
© Author(s) (or their
employer(s)) 2020. Re- use
permitted under CC BY- NC. No
commercial re- use. See rights
and permissions. Published by
BMJ.
ABSTRACT
There is a need for effective therapeutic options for
resistant patellar tendinopathy. Ultrasound (US)- guided
arthroscopic debridement has demonstrated promising
clinical results.
Objectives To prospectively evaluate pain, function,
tendon structure and adverse events after US and colour
Doppler (CD)- guided arthroscopic debridement for
persistent painful patellar tendinopathy.
Materials and methods Twenty- three consecutive
patients (19 males and 4 females, mean age 28 years
(±8), symptom duration 25 months (±21)), who had
failed conservative management including progressive
loading, were included. US+CD and ultrasound tissue
characterisation (UTC) examination veried the clinical
diagnosis and quantied baseline tendon structure.
Patients were treated with US+CD- guided arthroscopic
debridement followed by a specic rehabilitation protocol.
Outcomes were VISA- P score for pain and function and
UTC for tendon structure. Adverse events were specically
elicited.
Results At 6- month follow- up, mean VISA- P score
increased from 40 (±21.0) to 82 (±15) (mean deviation
(MD)=42.0, 95% CI 32 to 53, d=2.4), while organised echo
pixels (combined UTC type I+II) increased from 55.0%
(±17.0) to 69.0% (±15.0) (MD=14.0, d=0.7, 95% CI 2
to 21). Both outcomes exceeded minimum detectable
change values. Twenty- one participants returned to their
prediagnosis activity levels, and there were no signicant
adverse events.
Conclusions US- guided patellar tendon debridement for
persistent patellar tendinopathy improved symptoms and
tendon structure without complications at 6- month follow-
up. A majority (21/23) of the patients returned to their
preinjury activity level. Further studies with longer follow-
ups, preferably randomised and controlled, are needed.
INTRODUCTION
Patellar tendinopathy is a common overuse
condition and difficult to treat.1 2 Conserva-
tive management using loading regimens is
first line treatment. Both painful eccentric
quadriceps training3 4 and heavy- slow resis-
tance training5 have demonstrated promising
results, but certain subgroups cannot return
to full training and sports.6 7 Alternative
loading programmes, such as isometric exer-
cise approaches8 9, and adjunct interventions
such as Extracorporeal Shockwave Therapy10
and injection therapy,11–15 have shown mixed
and limited results.
Surgery is considered after failed
conservative treatment, but traditional
intratendinous approaches demonstrate
varying and unreliable results.16 17 Using
similar principles as polidocanol11 18 19 or
high volume12 13 20–22 injection, interference
with the peritendinous nerve and vessel rich
region outside the deep (dorsal) aspect of
the proximal patellar tendon,21 23 an US and
DP- guided arthroscopic- debridement proce-
dure has demonstrated positive outcomes in
four clinical studies.18 19 24–26
There is no clear relationship between
changes in structure, pain and function in
tendinopathy, with some therapies leading
to improved pain and function without
structural change27–29 while other therapies
leading to improved structure with changes
in pain.30 To evaluate structure, there is a
lack of objectivity and reliability using 2D
US+CD or MRI.31 Recently, ultrasound tissue
characterisation (UTC) has been used to visu-
alise tendon structure and quantify tendon
matrix integrity.32 33
This prospective case series aimed to
establish outcomes post- US+DP- guided
arthroscopic tendon debridement in
What are the new ndings
►Patellar tendinopathy is difcult to manage in active
athletes.
►Conservative management is not always successful.
►Traditional surgery is no better than exercise therapy.
►Patellar tendon debridement has demonstrated
promising results.
►There was signicant improvement in validated out-
come measures.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from

2MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803
Open access
participants with persistent painful patellar tendinop-
athy. Clinical status and function using the VISA- P, and
tendon structure using UTC, was used for evaluation.
MATERIAL AND METHODS
Participants presenting with persistent painful patellar
tendinopathy at Pure Sports Medicine (London, UK)
between August 2013 and October 2017 and could be
evaluated at 6 months, were included. There were 19
males and 4 females (mean age 28.1 years, ±8.2) with a
mean symptom duration of 24.8 months (±21.1). All had
previously failed conservative management including
progressive loading (eccentric training n=13; heavy
slow resistance n=10) and intermediate interventions
including injection therapy (cortisone n=8, high volume
n=5, sclerosing polidocanol n=1) or shockwave therapy
(n=10). All were active in sport including nine from
rugby, five from endurance running, four from football
and one from track and field, tennis, cricket, Gaelic foot-
ball and cross fit. Sixteen were elite athletes.
Ultrasound (US)+colour Doppler (CD) (GE logic E10)
was performed using a high frequency linear probe (MHz
6–15) with the participant in supine position with the
knee extended. In all subjects, US+CD showed a thick-
ened proximal patellar tendon with irregular structure
mainly deep and central in the tendon, including focal
hypoechoic regions and high blood flow arising from the
Hoffa’s fat pad and infiltrating into the focal hypoechoic
regions. There were also changes on the superficial
side of the tendon in 17 cases demonstrating localised
thickening of the paratenon including high blood flow
figure 1. In four cases, there was a bony spur or calcifica-
tion distal to the inferior pole of the patella.
UTC was performed with participants in a seated posi-
tion with the foot on the floor and the knee flexed to
100°. The transducer was placed perpendicular to the
long axis of the tendon. Using UTC, the echo struc-
ture of the patellar tendon was quantified for a distance
of 20 mm from the proximal insertion of the patellar
tendon to the mid- portion of the tendon. Contours were
performed on this region of interest prior to quantifica-
tion using a computer algorithm.32 33 Quantification was
expressed as a percentage of organised and disorganised
tissue with percentage of type I and II echopixels consis-
tent with organised tissue and type III and IV echopixels
consistent with disorganised tendon tissue.
Surgical procedure
US+CD- guided arthroscopic tendon debridement was
performed with general (n=5) or local anaesthesia
(n=18). Participants were supine with extended knee.
Standard anteromedial and anterolateral portals,
pressure- controlled pump and no tourniquet were used.
A routine arthroscopic evaluation of the knee joint was
performed. Simultaneous US examination (longitudinal
and transverse views) guided the procedure (figure 2).
Careful debridement was performed using a 4.5 mm full
radius blade shaver, aiming to remove vessels and nerves
adjacent to the tendinopathic change on the deep side of
the tendon (separating Hoffa’s fat pad from the patellar
tendon) (figure 3). This technique is based on previous
biopsy studies showing sensory and sympathetic nerves
located close to blood vessels.21 23
If coexisting pathology was present such as bony spur
or calcification at the inferior pole of the patella, careful
excision using a shaver was performed. In these cases, it
was necessary to also remove some tendinopathic tissue,
but emphasis was placed on removal of less tendon tissue.
The portals were sutured and 20 mL of local anaesthetic
(Levobupivacaine 2.5 mg/mL) was injected into the knee
joint.
Subsequently, the superficial part of the surgery
was performed. The decision to perform a superficial
scraping was based on focal superficial tendon tender-
ness on palpation together with abnormal US findings on
the superficial aspect of the proximal patellar tendon. Via
Figure 1 Blood vessels on supercial proximal patellar
tendon.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from

3
MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803
Open access
a vertical longitudinal incision in the skin and bursa, the
locally thickened paratenon was visualised (see figure 1).
The richly vascularised fatty infiltration located under the
paratenon on the superficial side of the tendon was care-
fully excised until normal underlying tendon tissue was
visualised. Careful haemostasis was achieved. Resorbable
sutures were used subcutaneously, and non- resorbable
sutures were used for the skin. Local compression was
applied.
Participants rested overnight and allowed to partially
weight- bear with crutches. All participants were reviewed
the next day. If a knee joint effusion was present, an aspi-
ration was performed under US- guidance using strict
sterile conditions. In the absence of any postoperative
complications such as a major superficial haematoma,
rehabilitation was started using a specific postoperative
rehabilitation plan (table 1). The general rehabilitation
principles were derived from an expert consensus state-
ment on rehabilitation of patellar tendinopathy,7 but
there was often a need to individualise the programme
dependent on the functional requirements of the partic-
ipants. Sutures were removed at 3 weeks. All participants
were reviewed at 6 months with clinical assessment and
collection of VISA- P and UTC results.
Outcome measures
The primary outcome measure was the VISA- P, to
evaluate the clinical outcome.34 This was completed inde-
pendently by the participant, in the absence of guidance
from the treating clinician, at both baseline (preopera-
tive) and 6 months (postoperative).
The secondary outcome measure was tendon structure
determined using UTC, measured by a single investigator
(LM) at baseline and at 6 months.
Participants were instructed to report adverse events to
a single investigator (LM).
All participants provided informed written consent for
inclusion in the study.
Statistical analysis
Statistical testing was completed using Microsoft Excel
for MacOS (Microsoft, Albuquerque, New Mexico, USA).
Mean differences and associated 95% CIs were calcu-
lated for all variables to reflect postoperative outcomes.
Figure 2 Surgical patellar tendon debridement procedure
using ultrasound guidance. Figure 3 Arthroscopic patellar tendon debridement using
ultrasound guidance.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from

4MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803
Open access
In addition, a Cohen’s d was calculated to determine the
size of identified interactions, interpreted as small (<0.2),
moderate (>0.5) and large (>0.8), respectively.35
RESULTS
Primary outcome (participant function)
VISA- P scores increased from 40.0 (±21.0) at baseline to
82.0 (±15.0) at 6- month follow- up (MD=42.0, d=2.4, 95%
CI 32 to 53). In addition, 21/23 participants returned to
their prediagnosis activity levels.
Secondary outcome (tendon structure)
Organised echo pixels (type I+II) increased from 55.0%
(±17.0) at baseline to 69.0% (±15.0) at 6- month follow- up
(MD=14.0%, d=0.7, 95% CI 2 to 21) (figure 4).
Adverse events
There was one knee joint effusion, presenting 1 day after
the procedure. This hemarthrosis was aspirated under
US guidance. There were no serious adverse events.
DISCUSSION
This case series demonstrated that US- guided patellar
tendon debridement for recalcitrant patellar tendinop-
athy improves pain, function and tendon structure at
6- month follow- up. A majority (21/23) of the partici-
pants returned to prediagnosis activity levels.
The most interesting finding in this study was the
significantly improved tendon structure at 6 months
after surgery. To the best of our knowledge, this finding
has never previously been demonstrated after surgical
patellar tendinopathy treatment. The relationship
between tendon structure and symptoms is contro-
versial, particularly in relation to changes that occur
following treatment. Some studies, using US and MRI,
have reported no relationship between improvements in
clinical symptoms and structural change.31 A more recent
systematic review including more reliable imaging tech-
niques such as UTC found that there was an association
between improvement in clinical symptoms and reduc-
tion in tendon thickness and neovascularisation.36 The
current study used UTC to define changes in aligned
fibrillar structure 6 months after surgery and demon-
strated significant improvement after arthroscopic
patellar tendon debridement. Recent studies have shown
that scanning of the patellar tendon in a similar position
demonstrates good intrarater and inter- rater reliability,
and intrarater minimal detectable change is estimated to
be 5.5%.37
The cause for the improvement in tendon structure
is unknown but could be directly related to this surgical
technique. This debridement surgery uses US and
CD to detect peritendinous regions with high blood
flow. Seminal studies assessing biopsies from patellar
tendinopathy tissue detected abnormal sensory and
sympathetic neural infiltration in close relation to blood
vessels in the peritendinous regions.21 23 Removing this
abnormal neural ingrowth through US- guided tendon
Table 1 Postoperative rehabilitation principles
Duration Rehabilitation principles
Week 1–2 Full weight bearing walking, range of motion exercises and quadriceps isometric exercises
Week 3–4 Introduction of closed- chain compound isotonic quadriceps exercises and proximal and distal kinetic chain
strengthening
Week 5–8 Progression of strength training to achieve strength goals: as a general rule, participants aim to squat body
weight and perform a single leg incline press at 1.5× body weight for at least eight repetitions per set
Week 9+ Introduction of plyometrics and sports specic training once strength goals achieved
Figure 4 Pre- UTC (above) and post- UTC (below)
ndings conrming increased organised (green) tissue
postdebridement. UTC, ultrasound tissue characterisation.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from

5
MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803
Open access
debridement could reduce pain and allow for more
aggressive rehab with improvement in symptoms and
structure. Alternatively, the positive effects of this surgery
could be attributable to indirect effects of enforced rest
and progressive rehab that would not have occurred if
surgery had not been performed. Further studies using
a reliable and quantifiable imaging modality, preferably
with randomisation and an exercise control group, are
required for more definitive conclusions to be drawn
about the cause of structural improvement in this type of
tendon surgery.
This surgical procedure is primarily extratendinous
and differs substantially from more traditional intra-
tendinous surgical techniques.16 38 There are several
advantages in using an extratendinous technique, the
most important being that it allows for early full weight-
bearing loading of the tendon. It could be argued
that a randomised study comparing the US- guided
arthroscopic debridement method with the traditional
intratendinous revision surgery should be performed.
However, this may raise issues since the results after
intratendinous revision surgery has been shown to be
poor and no better than non- operative treatment with
eccentric training.16
The US+CD- guided arthroscopic debridement is the
main surgical procedure during this treatment, but we
also did a minor superficial debridement procedure.
The justification for this superficial procedure is based
on our findings that many subjects with longstanding
symptoms have focal tenderness corresponding to US
findings of localised thickening of the paratenon on the
superficial surface of the proximal patellar tendon. Biop-
sies performed by our group (unpublished data) from
this superficial tissue reveal richly vascularised fatty infil-
tration containing abnormal sensory and sympathetic
nerves, which is similar innervation to the tissue on the
deep aspect of the proximal patellar tendon.23 There-
fore, it seems appropriate to excise this tissue. However,
the importance of this procedure to optimise clinical
outcome should be evaluated in a randomised controlled
trial.
This is a short- term follow- up study, but the positive
clinical outcomes demonstrated with this method are
not surprising since they are in keeping with results of
a previous randomised controlled trial and a 4- year
follow- up study19 25 26 on this procedure. In addition, this
method appears to be safe.
A limitation of this study is the lack of a control
group of enforced rest or exercise therapy. Therefore,
the changes in pain, function and structure cannot be
directly attributable to the surgical procedure but may
be related to the indirect effects of surgery or natural
history. However, as the majority of participants in this
study had long duration of symptoms and reduced func-
tion unresponsive to loading regimens, it seems unlikely
that the changes are entirely attributable to natural
history.
CONCLUSION
US- guided patellar tendon debridement for persistent
patellar tendinopathy improved symptoms and tendon
structure without complications at 6- month follow- up. A
majority (21/23) of the patients returned to their prein-
jury activity level. Further studies with longer follow- ups,
preferably randomised and controlled, are needed.
Twitter Lorenzo Masci @lorenzo_masci
Contributors LM was the main researcher and primary author. HA contributed to
the research and writing of the paper. BN contributed to the statistics and writing of
the paper. WWB was involved in data collection.
Funding The authors have not declared a specic grant for this research from any
funding agency in the public, commercial or not- for- prot sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in
the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication Obtained.
Ethics approval Ethical approval was granted by the Umea University, Umea
Sweden (Dnr 04-157 M).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Deidentied clinical and UTC data will be available
from rst author on reasonable request via email lorenzo@ sportdoctorlondon. com.
Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY- NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non- commercially,
and license their derivative works on different terms, provided the original work is
properly cited, appropriate credit is given, any changes made indicated, and the
use is non- commercial. See:http:// creativecommons. org/ licenses/ by- nc/ 4. 0/.
ORCID iD
LorenzoMasci http:// orcid. org/ 0000- 0002- 1094- 3040
REFERENCES
1 Khan KM, Maffulli N, Coleman BD, etal. Patellar tendinopathy: some
aspects of basic science and clinical management. Br J Sports Med
1998;32:346–55.
2 Kettunen JA, Kvist M, Alanen E, etal. Long- Term prognosis for
jumper's knee in male athletes: prospective follow- up study. Am J
Sports Med 2002;30:689–92.
3 Jonsson P, Alfredson H. Superior results with eccentric compared
to concentric quadriceps training in patients with jumper's knee: a
prospective randomised study. Br J Sports Med 2005;39:847–50.
4 Purdam CR, Jonsson P, Alfredson H, etal. A pilot study of the
eccentric decline squat in the management of painful chronic
Patellar tendinopathy. Br J Sports Med 2004;38:395–7.
5 Kongsgaard M, Kovanen V, Aagaard P, etal. Corticosteroid
injections, eccentric decline squat training and heavy slow
resistance training in Patellar tendinopathy. Scand J Med Sci Sports
2009;19:790–802.
6 Cook JL, Khan KM. What is the most appropriate treatment for
Patellar tendinopathy? Br J Sports Med 2001;35:291–4.
7 Malliaras P, Cook J, Purdam C, etal. Patellar tendinopathy: clinical
diagnosis, load management, and advice for challenging case
presentations. J Orthop Sports Phys Ther 2015;45:887–98.
8 Rio E, Kidgell D, Purdam C, etal. Isometric exercise induces
analgesia and reduces inhibition in Patellar tendinopathy. Br J Sports
Med 2015;49:1277–83.
9 Rio E, Purdam C, Girdwood M, etal. Isometric Exercise to Reduce
Pain in Patellar Tendinopathy In- Season: Is It Effective "on the
Road"? Clin J Sport Med 2019;29:188–92.
10 Korakakis V, Whiteley R, Tzavara A, etal. The effectiveness of
extracorporeal shockwave therapy in common lower limb conditions:
a systematic review including quantication of patient- rated pain
reduction. Br J Sports Med 2018;52:387–407.
11 Hoksrud A, Ohberg L, Alfredson H, etal. Ultrasound- Guided
sclerosis of neovessels in painful chronic Patellar tendinopathy: a
randomized controlled trial. Am J Sports Med 2006;34:1738–46.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from

6MasciL, etal. BMJ Open Sp Ex Med 2020;6:e000803. doi:10.1136/bmjsem-2020-000803
Open access
12 Maffulli N, Del Buono A, Oliva F, etal. High- Volume image- guided
injection for recalcitrant Patellar tendinopathy in athletes. Clin J
Sport Med 2016;26:12–16.
13 Morton S, Chan O, King J, etal. High volume image- guided
injections for Patellar tendinopathy: a combined retrospective
and prospective case series. Muscles Ligaments Tendons J
2014;4:214–9.
14 Scott A, LaPrade RF, Harmon KG, etal. Platelet- Rich plasma for
Patellar tendinopathy: a randomized controlled trial of Leukocyte-
Rich PrP or Leukocyte- Poor PrP versus saline. Am J Sports Med
2019;47:1654–61.
15 van Ark M, Zwerver J, van den Akker- Scheek I. Injection treatments
for Patellar tendinopathy. Br J Sports Med 2011;45:1068–76.
16 Bahr R, Fossan B, Løken S, etal. Surgical treatment compared
with eccentric training for Patellar tendinopathy (jumper's
knee). A randomized, controlled trial. J Bone Joint Surg Am
2006;88:1689–98.
17 Coleman BD, Khan KM, Maffulli N, etal. Studies of surgical
outcome after Patellar tendinopathy: clinical signicance of
methodological deciencies and guidelines for future studies.
Victorian Institute of sport tendon Study Group. Scand J Med Sci
Sports 2000;10:2–11.
18 Willberg L, Sunding K, Forssblad M, etal. Sclerosing polidocanol
injections or arthroscopic shaving to treat Patellar tendinopathy/
jumper's knee? a randomised controlled study. Br J Sports Med
2011;45:411–5.
19 Sunding K, Willberg L, Werner S, etal. Sclerosing injections and
ultrasound- guided arthroscopic shaving for Patellar tendinopathy:
good clinical results and decreased tendon thickness after surgery- a
medium- term follow- up study. Knee Surg Sports Traumatol Arthrosc
2015;23:2259–68.
20 Alfredson H, Forsgren S, Thorsen K, etal. Glutamate NMDAR1
receptors localised to nerves in human Achilles tendons.
Implications for treatment? Knee Surg Sports Traumatol Arthrosc
2001;9:123–6.
21 Forsgren S, Danielson P, Alfredson H. Vascular NK-1 receptor
occurrence in normal and chronic painful Achilles and Patellar
tendons: studies on chemically unxed as well as xed specimens.
Regul Pept 2005;126:173–81.
22 Forsgren S, Alfredson H, Andersson G. Further proof of the
existence of a non- neuronal cholinergic system in the human
Achilles tendon: presence of the AChRα7 receptor in tendon
cells and cells in the peritendinous tissue. Int Immunopharmacol
2015;29:195–200.
23 Danielson P, Andersson G, Alfredson H, etal. Marked sympathetic
component in the perivascular innervation of the dorsal
paratendinous tissue of the Patellar tendon in arthroscopically
treated tendinosis patients. Knee Surg Sports Traumatol Arthrosc
2008;16:621–6.
24 Alfredson H, Masci LA, Ultrasound ML. Ultrasound and Doppler-
Guided Surgery for the Treatment of Jumper’s Knee in Professional
Rugby Players. Pain Studies and Treatment 2015;03:1–5.
25 Willberg L, Sunding K, Ohberg L, etal. Treatment of jumper's
knee: promising short- term results in a pilot study using a new
arthroscopic approach based on imaging ndings. Knee Surg Sports
Traumatol Arthrosc 2007;15:676–81.
26 Willberg L, Sunding K, Forssblad M, etal. Ultrasound- and Doppler-
guided arthroscopic shaving to treat jumper's knee: a technical note.
Knee Surg Sports Traumatol Arthrosc 2007;15:1400–3.
27 de Jonge S, de Vos RJ, Weir A, etal. One- Year follow- up of
platelet- rich plasma treatment in chronic Achilles tendinopathy: a
double- blind randomized placebo- controlled trial. Am J Sports Med
2011;39:1623–9.
28 de Vos RJ, Heijboer MP, Weinans H, etal. Tendon structure's lack
of relation to clinical outcome after eccentric exercises in chronic
midportion Achilles tendinopathy. J Sport Rehabil 2012;21:34–43.
29 Dragoo JL, Braun HJ, Durham JL, etal. Comparison of the
acute inammatory response of two commercial platelet- rich
plasma systems in healthy rabbit tendons. Am J Sports Med
2012;40:1274–81.
30 Malliaras P, Barton CJ, Reeves ND, etal. Achilles and patellar
tendinopathy loading programmes : a systematic review comparing
clinical outcomes and identifying potential mechanisms for
effectiveness. Sports Med 2013;43:267–86.
31 Drew BT, Smith TO, Littlewood C, etal. Do structural changes (EG,
collagen/matrix) explain the response to therapeutic exercises in
tendinopathy: a systematic review. Br J Sports Med 2014;48:966–72.
32 van Schie HTM, de Vos RJ, de Jonge S, etal. Ultrasonographic
tissue characterisation of human Achilles tendons: quantication of
tendon structure through a novel non- invasive approach. Br J Sports
Med 2010;44:1153–9.
33 Docking SI, Daffy J, van Schie HTM, etal. Tendon structure changes
after maximal exercise in the thoroughbred horse: use of ultrasound
tissue characterisation to detect in vivo tendon response. Vet J
2012;194:338–42.
34 Mendonça LdeM, Ocarino JM, Bittencourt NFN, etal. The accuracy
of the VISA- P questionnaire, Single- Leg decline squat, and tendon
pain history to identify Patellar tendon abnormalities in adult
athletes. J Orthop Sports Phys Ther 2016;46:673–80.
35 Sullivan GM, Feinn R. Using effect Size- or why the P value is not
enough. J Grad Med Educ 2012;4:279–82.
36 Rabello LM, van den Akker- Scheek I, Brink MS, etal. Association
between clinical and imaging outcomes after therapeutic loading
exercise in patients diagnosed with Achilles or Patellar tendinopathy
at short- and long- term follow- up: a systematic review. Clin J Sport
Med 201810.1097/JSM.0000000000000624. [Epub ahead of print:
25 Jun 2018].
37 van Ark M, Rabello LM, Hoevenaars D, etal. Inter- and intra- rater
reliability of ultrasound tissue characterization (UTC) in Patellar
tendons. Scand J Med Sci Sports 2019;29:1205–11.
38 Khan KM, Visentini PJ, Kiss ZS, etal. Correlation of ultrasound and
magnetic resonance imaging with clinical outcome after Patellar
tenotomy: prospective and retrospective studies. Victorian Institute
of sport tendon Study Group. Clin J Sport Med 1999;9:129–37.
copyright. on July 23, 2020 by guest. Protected byhttp://bmjopensem.bmj.com/BMJ Open Sport Exerc Med: first published as 10.1136/bmjsem-2020-000803 on 22 July 2020. Downloaded from