The value of Platelet-Rich Plasma injections in the treatment of the jumper's knee: a double-blind randomised trial

The jumper's knee is a degenerative condition at the insertion of the patellar
tendon at the distal patellar pole. Etiologic factors include aging and
mechanic load. The condition thus affects mostly sportsmen. The prevalence
among sportsmen is about 14% and an additional 8% had symptoms in the past.
Among elite volleyball players the prevalence is 40-50%. The most frequent
applied therapy is eccentric training. However, a significant part of the
patients keep having symptoms. Extracorporal shockwave therapy, local applied
glyceryl trinitrate and sclerosant injections have only showed an average
effect. In recent days progress is achieved in the treatment of tendinopathies.
Studies were published about the effects of *dry needling*, intratendinous
autologous blood injections and intratendinous *platelet-rich plasma*(PRP)
injections. However, no studies were published regarding the effects of
intratendinous autologous blood injections in comparison with the effects of
PRP-injections, nor regarding the effects of intratendinous PRP-injections in
the treatment of the jumper's knee.

There is a double study objective:
- First the effects of a PRP-injection in the treatment of the jumper's knee
in comparison with the effects of a placebo injection
- Second the effects of a PRP-injection in comparison with the effects of an
autologous blood injection

Previous studies showed that autologous blood injections in the treatment of
the jumper's knee resulted in a decrease of symptoms. Study population will be
divided into three groups.

Sports physicians, general practitioners, physiotherapists and orthopedic
surgeons in the region of Utrecht/Amersfoort will receive an information paper
about this study, including the request to refer patients matching the
inclusion criteria to the study location, sports medicine department, Meander
MC, in Baarn.
Inclusion criteria:
- pain at the inferior pole of the patella for 3 months
- age 18-55 year
- tendinosis or thickening compared with the contralateral side of > 3 mm,
detected with ultrasonography or MRI
- already undergone eccentric training for 6 weeks following a standardised
protocol

Exclusion criteria:
- pregnancy
- injection in the patellar tendon in the last 3 months, irrespective of the
applied substance
- operations on the patellar tendon in the past
- calcifications in the proximal patellar tendon
- at examination indications for intraarticular pathology or patellofemoral
pain syndrome
- chronic NSAID use in the past 3 months

The intake will include physical examination, assessment of the VISA-P score
using a questionnaire and the VAS score and ultrasonography of both patellar
tendons to show an area of tendinosis. Also the diameter of the proximal tendon
and the number of neovessels will be determined. Then patients will be
randomised into three matching groups (group 1 placebo injection, group 2
autologous blood injection, group 3 PRP-injection). 27 cc of blood will be
collected from all patients from the antecubital fossa to obtain 3 cc of PRP,
using the mini GPS II system of Biomet. Preparation time will be 15 minutes.
Then local anaesthesia will be applied using lidocaine. After this the tendon
will be 'dry-needled' 5 times under ultrasound guidance and, depending on
randomisation, the right fluid will be injected. All this will occur
double-blind, because the syringe will be blinded and the intervention will be
executed by a physician who is not involved in the follow-up.

Following the injection the first two weeks activities more strenuous than
daily life (e.g. jumping and running) are forbidden. Then a standardised
physiotherapy protocol under the supervision of a physiotherapist is conducted
to aid rehabilitation. After three months a second ultrasonography will assess
tendinosis, thickness of the tendon and number of neovessels. Follow-up
including VISA-P score, VAS score and physical examination will take place
after 6, 12, 26 and 52 weeks. Primary outcome measure will be VISA-P score.
This is a valid scoring system to assess jumper's knee, 100 points maximum,
meaning normal functioning knee and 0 points minimum. Secondary outcome
measures will be VAS score, return to sports (extent and level), degree of
ultrasound pathology and costs.

27 cc of blood will be collected from all patients from the antecubital fossa
to obtain 3 cc of PRP, using the mini GPS II system of Biomet. Preparation time
will be 15 minutes. Then local anaesthesia will be applied using lidocaine.
After this the tendon will be 'dry-needled' 5 times under ultrasound guidance
and, depending on randomisation, the right fluid will be injected.

Patients are asked to visit the sports medicine department 5 times. On two or
three occasions ultrasonography of the patellar tendon will take place
(depending on what kind of imaging already took place). 27 cc of blood will be
collected. All patients receive an injection at the site of the tendinosis.
There is a small risk of infection, as with every injection, but no infections
have been reported in earlier studies. Except for a short (maximum 1 week)
aggrevation of the pain, no other risks or side effects have been reported in
earlier studies.