Effectiveness of Radial Shockwave Therapy compared to Focused Shockwave Therapy for treating patellar tendinopathy

Patellar tendinopathy ('jumper's knee') is a clinical condition of gradually
progressive activity-related pain at the insertion of the patellar tendon at
the apex patellae. Prolonged repetitive stress of the knee-extensor apparatus
can lead to this common overuse tendinopathy in athletes from different sports.
The high prevalence, low function scores, and chronic nature of the condition
mean that in some jumping sports, patellar tendinopathy may cause at least as
much impairment in athletic performance as acute knee injuries.
New treatment modalities for patellar tendinopathy have recently been
introduced, based on the findings that the pathology underlying chronic
(patellar) tendinopathies is not inflammatory tendinitis but a degenerative
tendinosis due to a failed healing response.

Extracorporeal shockwave therapy (ESWT) is a method for treating tendinopathies
that was originally used for lithotripsy (kidney stone fragmentation). In the
last few years, extracorporeal shockwave therapy (ESWT) has also been used for
the treatment of patellar tendinopathy. Based on randomized controlled trials
(RCT) both Taunton and Peers concluded that focused ESWT improves pain and
function in subjects with patellar tendinopathy. Wang recently published the
results of a RCT and concluded that ESWT appeared more effective and safer than
traditional conservative treatments in the management of patients with chronic
patellar tendinopathy. Therefore, ESWT seems useful in the treatment of chronic
patellar tendinopathy and at least as effective as other conservative
treatments, 12 weeks of eccentric training or surgery.
ESWT uses focused shock waves to treat the affected area. Recently, shockwave
machines have been introduced that do not generate focused shockwaves. These
machines have a ballistic source (a method not originating from lithotripsy)
that generates radial shockwaves. Lohrer used this radial shockwave therapy
(RSWT) to treat patellar tendinopathy. Lohrer demonstrated significant effects
on pain and function suggesting that radial shockwave therapy seems to be an
effective treatment for patellar tendinopathy as well. Their study however was
non-randomised and had no control group, making it difficult to draw firm
conclusions. Physical therapists most often use RSWT-machines because they are
better affordable.
Till now however, no studies have directly compared the effect of Focused
Shockwave Therapy (FSWT) and RSWT in patellar tendinopathy. In the current
study we will therefore compare the effectiveness of radial shockwave therapy
and focused shockwave therapy in patellar tendinopathy.

The primary objective is to determine the effectiveness of RSWT versus FSWT in
treating patellar tendinopathy.

Double blinded, randomized controlled study using a 2 group repeated measures
design with a pre-treatment period of 1 week, a treatment period of 2 weeks (3
treatments with a 1 week interval) and a 12 week follow-up (see flowchart).

Subjects who visit the Sports Medicine Center, are diagnosed with patellar
tendinopathy by one of the sports medicine physicians and are willing to
cooperate with the study, will receive either FSWT or RWST. Treatment will be
given by an independent physical therapist. At the start of the study (T1),
before each treatment (T2-T4) and 1 week (T5), 4 week (T6), 7 week (T7) and 12
week (T8) after the last treatment outcome parameters will be assessed by the
investigator.
At each evaluation subjects will complete the VISA questionnaire. At T2, T7 and
T8 subjects will perfom a functional test (decline squat). The subjects from
both groups will also rate their satisfaction with the treatment. Treatment and
functional tests will take place at the University Sports Medicine Center.

FSWT treatment and RSWT treatment will be given by an independent physical
therapist. Shockwaves will be applied according to the guidelines of the
International Society for Musculoskeletal Shockwave Therapy (ISMST) using a
shockwave machine that can generate both focused and radial shockwaves
(Duolith, Storz, Germany). Shockwaves will be administered in three sessions at
one-week intervals using 2000 impulses at a frequency of 4 Hz. The energy flux
density will be 0,20 mJ/mm2. Beside shockwave treatment, both treatment groups
will be given a standard home programme for tendon training.

Shockwave therapy appears to be an effective treatment so this can be of great
benefit to the subject receiving this treatment. On the other hand, the risks
and the burden for the subjects both are low. There are no extra visits to the
University Sports Medicine Center required compared to regular treatment.
Subjects can continue to participate in their sporting activities during the
study. No (serious) side effects of shockwave therapy have been reported with
the energy flux density used in this study. So the potential high benefit and
the low risk and burden to the subject justify this relevant study.