Is there evidence to support the use of Platelet-rich plasma (PRP) in regenerating partial anterior cruciate ligament (ACL) tears?

PRP for Partial ACL Tears: Current Evidence

There is insufficient evidence to routinely recommend PRP for regenerating partial ACL tears, though it may be considered as an adjunct to conservative management in select cases where patients strongly prefer to avoid surgery and accept the uncertain benefit.

Critical Evidence Gap

The evidence provided focuses primarily on rotator cuff injuries, not ACL tears 1. The American Academy of Orthopaedic Surgeons guidelines state that limited evidence does not support routine use of PRP for rotator cuff tendinopathy or partial tears 1. While this is a different anatomical structure, it reflects the broader uncertainty about PRP efficacy in partial ligamentous/tendinous injuries.

What We Know About PRP in General

• PRP preparations are clinically safe but suffer from severe lack of standardization in preparation methods, terminology, purity, content, and quality control 1, 2
• The International Society on Thrombosis and Haemostasis rated PRP as uncertain for tendon injuries and sports injuries (median scores 4-6.5 out of 9) 2
• Different preparation techniques result in significant variations in platelet yields, concentration, purity, and activation status, directly impacting clinical efficacy 1

Limited ACL-Specific Evidence

The available research on PRP for partial ACL tears consists only of low-quality case series (Level 4 evidence):

• A 2022 systematic review found no clinical superiority when using PRP in ACL reconstruction, and for partial ACL tears, only case series exist—no randomized controlled trials 3
• A 2024 retrospective case series showed all patients regained ligament continuity and returned to sport, but one patient re-ruptured after return to activity 4
• A single 2019 case report described improvement after three PRP injections, but this represents the weakest form of evidence 5

Clinical Decision Algorithm

If considering PRP for partial ACL tear:

1. First, determine injury severity and patient activity level

   • Grade 1 or proximal-based grade 2 injuries may respond better to conservative approaches 6
   • Highly active patients seeking early return to sport may be candidates 4

2. Set realistic expectations with the patient

   • Evidence is based only on case series, not controlled trials 3
   • Re-rupture risk exists even with apparent ligament healing 4
   • Standard recovery time is approximately 4-5 months 4

3. If proceeding with PRP:

   • Administer within 6 weeks of injury 4
   • Plan for 2-3 PRP sessions on average 4
   • Use ultrasound guidance for accurate delivery 5
   • Combine with structured rehabilitation—PRP alone is insufficient 3
   • Confirm ligament continuity with MRI before full return to sport 4

Critical Pitfall to Avoid

Do not present PRP as an evidence-based treatment for partial ACL tears. The analogy to ulnar collateral ligament (UCL) injuries in overhead athletes shows better outcomes with PRP 6, but this cannot be extrapolated to ACL injuries without appropriate trials. The field lacks the randomized controlled trials needed to establish efficacy 3.

Bottom Line for Clinical Practice

Given the absence of high-quality evidence, conservative management with structured rehabilitation remains the standard approach for partial ACL tears. PRP may be offered as an experimental adjunct for motivated patients who understand the uncertain benefit, particularly those with grade 1-2 injuries who wish to avoid surgery 3, 4. However, the lack of standardization in PRP preparation means outcomes may vary significantly between providers 1, 2.