Courtesy: Dr Anthony Luke, UCSF San Francisco

Platelet-Rich Plasma (PRP) is one of the most commonly used orthobiologic therapies in orthopaedics and sports medicine.

Orthobiologics Include

PRP
Bone marrow aspirate concentrate
Mesenchymal stem cells

Among these, PRP is the most widely used due to its simplicity and safety

Platelet Biology and Function

Platelet Characteristics

~250 million platelets per mL of blood
Contain intracellular granules rich in:
- Growth factors
- Cytokines

Biological Roles

Platelets contribute to:

Hemostasis
Inflammation regulation
Angiogenesis
Tissue repair
Extracellular matrix production

History of PRP

Scientific Background

Platelet research dates back to the 19th century

Milestones

1940s – Discovery of growth factors
1980s – Clinical use in wound healing
1990s – Maxillofacial surgery applications
Early 2000s – Adoption in orthopaedics

Popularization

PRP gained global attention through use in elite athletes such as:

Kobe Bryant (knee treatment)
Rafael Nadal (chronic knee injuries)

Definition of PRP

Current Definition

Autologous plasma with platelet concentration higher than baseline

Evolution of Definition

Earlier: -3–5× baseline platelet concentration
Current: Any level above baseline

Preparation of PRP

Basic Steps

Blood collection
Centrifugation
Separation into layers:
- Red blood cells (bottom)
- Buffy coat (middle)
- PRP (top)
Collection of platelet-rich plasma

Centrifugation Methods

Single-spin technique
Double-spin technique

Different systems produce variable platelet concentrations

Growth Factors in PRP

Key Growth Factors

PDGF
TGF-Beta
VEGF
IGF
EGF

Functions

Angiogenesis
Cell proliferation
Collagen synthesis
Modulation of inflammation

Variability in PRP Preparations

Factors Affecting PRP Composition

Centrifugation technique
Commercial systems
Platelet concentration
Leukocyte content
Patient variability

This variability leads to difficulty comparing studies

Types of PRP

Leukocyte-Rich PRP

Contains white blood cells
Higher inflammatory response

Leukocyte-Poor PRP

Reduced leukocyte content
Preferred for:
- Intra-articular injections
- Most orthopaedic indications

PRP Activation

Methods

Calcium chloride
Thrombin
Mechanical activation

Many clinicians rely on natural activation after injection

Orthopaedic Indications for PRP

1. Tendon Disorders

Lateral epicondylitis
Achilles tendinopathy
Patellar tendinopathy
Rotator cuff tendinopathy

2. Muscle Injuries

Hamstring injuries
Muscle strains

3. Ligament Injuries

Partial tears
Adjunct in ligament reconstruction

4. Joint Disorders

Knee osteoarthritis
Early cartilage degeneration

PRP in Knee Osteoarthritis

Comparative Outcomes

Treatment	Duration of Relief
Corticosteroids	6–12 weeks
Hyaluronic acid	6–8 months
PRP	Up to 12 months

Key Findings

Better than corticosteroids
Slightly superior to hyaluronic acid

Number of PRP Injections

Common Protocols

Single injection
2–3 injections spaced 2–6 weeks apart

Optimal protocol remains uncertain

Procedure Considerations

Local Anesthesia

Generally avoided
May reduce platelet activity

Image Guidance

Recommended for:

Tendons
Deep joints
Small structures

Post-Injection Protocol

Medications

Avoid NSAIDs:
- 1 week before
- 1 week after
Use paracetamol for pain

Activity

Relative rest
Gradual return to activity

Tendon Treatments

May require:
- Immobilization
- Bracing
- Activity modification

Advantages of PRP

Autologous (no immune reaction)
Minimal infection risk
No disease transmission
Stimulates biological healing

Limitations and Controversies

Lack of standardization
Variable platelet concentrations
Inconsistent study results
Limited high-quality RCTs

Future Directions

Research Focus

Identifying key growth factors
Determining optimal platelet concentration
Standardizing preparation methods

Emerging Therapies

Bone marrow aspirate concentrate
Stem cell therapies

Key Take-Home Messages

PRP is a widely used and safe orthobiologic therapy
Most useful in:
- Knee osteoarthritis
- Tendinopathies

Clinical Insight

Results are variable due to lack of standardization
Further high-quality research is needed

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