Effect of Collagen/Vitamin C in Jumper's Knee; a RCT

Rationale: Patellar tendinopathy (PT) is a tendon overuse injury with high prevalence rates in elite and recreational athletes. PT sometimes results in a prolonged absence from sport participation, hampering individuals to achieve their desired performance levels and to benefit from the health related effects of sports participation. Many treatment options are used but management of PT remains challenging. Current treatment involves progressive education, load management and tendon loading exercises (PTLE). Recent studies have shown that nutrition can positively affect collagen synthesis in musculoskeletal tissues. A study showed that supplementing 15g of gelatine combined with 50mg of Vitamin C, 1 hour before loading exercises, resulted in an increase in whole body collagen synthesis and increased mechanics and collagen content of human engineered ligaments. However the effectiveness of oral supplementation of hydrolysed collagen in combination with vitamin C in athletes with PT has not been studied in a randomized controlled trial yet.

Objective: The primary aim of this RCT is to evaluate whether the use of oral supplementation of hydrolysed collagen/vitamin C in addition to usual care (education, load management and PTLE) is superior to usual care and placebo on VISA-P score after 12, 24 and 52 weeks for athletes with PT. The secondary aim of this RCT is to evaluate whether the use of oral supplementation of hydrolysed collagen/vitamin C in addition to usual care (education, load management and PTLE) is superior to usual care and placebo on other clinical outcome parameters, functional tests and tendon structure after 12 and 24 weeks for athletes with PT.

Study design: The JUMPFOOD-study is a double blinded, 2-armed randomized placebo controlled trial which investigates the effectiveness of oral supplementation of hydrolysed collagen and vitamin C combined with progressive tendon loading exercise compared to only progressive tendon loading exercises in athletes with PT.

Study population: Recreational, competitive and professional male and female athletes from different kinds of sports will be included. Inclusion criteria: age 16-40 years old; history of focal knee pain for at least 12 weeks localized in the region of the patellar tendon in association with training and competition; playing sports for at least once a week for at least one year; palpation tenderness to the corresponding painful area on the patellar tendon; Victorian Institute of Sports Assessment - Patella (VISA-P) score < 80 out of 100 points.

Intervention: The intervention consists of a nutritional supplement with 10g hydrolysed collagen and 40 mg vitamin C, in comparison to a placebo supplement consisting of maltodextrin. All participants in both groups will receive education, load management advices and a criteria-based PTLE consisting of 4 stages within the limits of pain during 24-weeks. This (training) intervention has recently been proven to be superior to eccentric training. Participants will be randomly assigned to receive either the nutritional supplement collagen/vitamin C (intervention) or a placebo supplement.

Main study parameters/endpoints: The primary outcome measure will be the change in the Dutch version of the VISA-P score. This simple, validated, reliable and injury-specific questionnaire scores the severity of patellar tendinopathy and is sensitive to small changes in symptoms. It was specifically designed for patellar tendinopathy, rating pain, symptoms, simple test of function and the ability to participate in tendon-loading sports [1]. A VISA-P score of 100 indicates no pain, maximum function and maximum ability to play sports. The score decreases with increasing severity of symptoms of PT. The VISA-P questionnaire will be self-administered at baseline, and after 6, 12, 18, 24 and 52 weeks follow-up. Secondary outcomes will include: Pain during functional tests, advanced imaging methods and tendon structure and stiffness measurements (MRI, ultrasound, UTC, Myoton), blood levels of amino acids and inflammatory markers measured in blood, and dietary habits, that will all be measured at baseline, at 12 weeks and at 24 weeks of follow-up. In addition, data on the compliance with the exercise program and supplement intake, training and competition load will be collected weekly using an online questionnaire.