Background: Tendon injuries account for 30 to 50 percent of all sports-related injuries. Achilles tendinopathy can affect sports performance and activities of daily living, and is often recalcitrant to conservative treatments; 25 to 45 percent of patients eventually need surgery. The terms “tendinopathy” and “tendinosis” are more commonly used now instead of “tendinitis,” because the condition characterized by pain, swelling, and decreased activity is not from acute inflammation as much as from abnormal tissue repair and chronic damage to the tendon fibers. Eccentric exercise (stretching the Achilles tendon while concurrently contracting the calf muscle) has been the mainstay of rehabilitation.

Platelet-rich plasma (PRP) injections into ligaments and tendons have been postulated to stimulate the body's own healing mechanisms with the release of growth factors that stimulate tissue repair, and there is also evidence that PRP injections are being used more often in clinical practice. The injection is created by centrifuging a sample of the patient's blood and injecting several milliliters of the platelet-rich portion. Laboratory-based studies have shown some benefit, but well-designed clinical studies had not been done. In this trial, de Vos and colleagues studied if PRP injections would improve pain and functional outcome in chronic Achilles tendinopathy when added to the usual care of eccentric exercise.

The Study: This stratified, block-randomized, double-blind, placebo-controlled trial was performed at a sports medicine center in the Netherlands. Persons 18 to 70 years of age who had chronic midportion Achilles tendinopathy (i.e., symptoms for at least two months, located 2 to 7 cm proximal to the tendon insertion at the calcaneus) were included in the trial. Those with suspected tendon rupture or other tendon insertion injuries, systemic inflammatory conditions, fluoroquinolone use (which can cause tendinopathy), previous participation in a rehabilitation program, or previous PRP injection were excluded. To adequately power the study, a sample size of 54 participants was randomized into two groups. Under ultrasound guidance, the intervention group received a 4-mL injection of PRP; the control group was injected with the same amount of saline. Both groups had a prescribed rehabilitation program and continued to use eccentric exercises.

The primary outcomes were levels of pain and activity at baseline and at six, 12, and 24 weeks, as measured using the Victorian Institute of Sports Assessment-Achilles (VISA-A) questionnaire. This validated assessment uses a scale ranging from 0 to 100; higher scores indicate less pain and more activity. Secondary outcomes included subjective patient satisfaction, return to sports participation, and adherence to eccentric exercises.

Results: At 24 weeks, the PRP group had improved their VISA-A score by 21.7 points, and the placebo group improved their score by 20.5 points, indicating no significant difference in the primary outcome. There were also no significant differences between groups for the secondary outcomes.

Conclusion: The authors conclude that injection with PRP in addition to traditional eccentric exercise does not significantly improve levels of pain or activity at six, 12, or 24 weeks. They do not recommend adding PRP injections to the treatment of chronic midportion Achilles tendinopathy.