Tendon injuries are frustrating.
They take time, don’t always follow a clear path, and often linger longer than expected.
Whether you're managing patellar tendinopathy, Achilles issues, or a rotator cuff injury, understanding how tendons heal is essential for guiding smart return-to-play decisions.
Here’s a breakdown of the three stages of tendon healing, along with what you should be doing during each one.
Stage 1: Inflammation (0–48 Hours)
What’s Happening Biologically
- After injury, immune cells such as neutrophils and macrophages flood the site.
- These cells release cytokines and growth factors (like Interleukin-1β, TGF-β, VEGF) that begin the repair process.
- Platelets release healing signals to activate downstream regeneration.
This stage is like demolition and debris removal, it’s messy but absolutely necessary.
Training and Treatment
- Avoid total rest, but also avoid stressing the tendon. Use relative rest.
- Focus on unloading strategies like taping, offloading positions, or modified movement.
- Maintain general cardiovascular and physical capacity through cross-training.
- If needed, use modalities for symptom management, but understand they don’t accelerate healing.
Stage 2: Proliferation (3 Days to 4 Weeks)
What’s Happening Biologically
- Fibroblasts and tenocytes begin forming a collagen type III scaffold.
- This scaffold provides structure, but it’s weak and disorganized.
- Tendon-derived stem cells and mesenchymal stem cells support tissue regeneration.
This stage is like framing the house—you have structure now, but it’s not ready for heavy use.
Training and Treatment
- Begin with isometrics to modulate pain and introduce gentle tendon loading.
- Progress to isotonic loading (concentric and eccentric) based on pain tolerance.
- Avoid fast, ballistic, or chaotic movement.
- Maintain overall conditioning and strength outside the injured tissue.
Stage 3: Remodeling (1 Month to 2 Years)
What’s Happening Biologically
- Collagen III is gradually replaced by collagen type I, which is stronger and better organized.
- Collagen fibers begin to align along lines of mechanical stress.
- Final remodeling involves cross-linking and reorganization of the extracellular matrix, which restores tendon stiffness and load tolerance.
This is the remodeling and reinforcement phase—the tissue becomes stronger and more functional over time.
Training and Treatment
- Introduce heavy slow resistance and progressive eccentric loading.
- Add energy storage and release activities like plyometrics, running, and deceleration work.
- Ensure gradual exposure to high-speed and sport-specific demands.
- Monitor volume and intensity closely to avoid re-aggravation.
What This Means for Coaches
Tendon healing is a long, nonlinear process.
However, with a clear understanding of biology and loading principles, coaches can play a vital role in recovery. Here's what to remember:
- Match treatment and training to the current tissue stage—don’t rush or overprotect.
- Pain levels can improve before tissue strength is restored—be cautious with early clearance.
- Load is medicine—but only when applied at the right time and in the right dose.
Practical Takeaways
- Inflammation is part of the process so don’t overreact to it.
- During proliferation, the tendon is healing but fragile so begin loading with care.
- Remodeling takes months or even years and progressive loading is essential.
- Return-to-play decisions should account for tissue readiness, not just pain levels.
- Coaches and rehab professionals must work together—healing requires both strategy and patience.
