Spring Running Injuries: Why They Happen and How to Avoid Them
Every spring, it plays out the same way. The weather finally breaks, the roads dry out, and runners who took a few months off lace up with genuine excitement. The first run feels great. The second one too. By week three, something starts to complain — an Achilles that's a little stiff in the morning, a knee that aches on the stairs, a shin that didn't hurt yesterday but definitely hurts today.
If this has happened to you, you probably blamed yourself for going out too fast or skipping your warmup. But the real reason is more interesting than that — and understanding it will change how you approach every spring season going forward.
Your Fitness Came Back Faster Than Your Tendons Did
Here's the thing about the human body: not all tissues adapt at the same rate.
Your cardiovascular system is remarkably responsive. After a few weeks of consistent running, your heart rate drops, your breathing improves, and your perceived effort decreases. You feel fit — because aerobically, you largely are.
Your tendons and connective tissue work on a completely different timeline.
Tendons — the Achilles, the patellar tendon at the knee, the plantar fascia at the foot — are dense, relatively avascular structures. They respond to load, but slowly. Meaningful structural adaptation takes weeks to months, not days. When you return to running after a winter of reduced activity, your tendons are starting from a lower baseline than your lungs are.
This mismatch is the root cause of most spring running injuries. You feel ready. Your cardiovascular system says go. Your tendons are still catching up — and if the load increases faster than their capacity to adapt, something gives.
What "Overloading a Tendon" Actually Means
Tendon injuries don't usually happen because of one bad run. They happen because of cumulative load that exceeds the tissue's current capacity repeatedly over days or weeks.
A tendon that's being asked to do more than it's ready for will often give you early warning signs: stiffness in the first few minutes of activity that warms up and goes away, mild soreness the morning after a run, a vague sense of tightness that you've been ignoring. These signals are easy to dismiss, especially when the discomfort disappears once you're moving.
The problem is that "warms up and goes away" doesn't mean the tissue is fine. It means the tendon is irritated but still functional. If the load keeps increasing with more miles, more pace, and more days, that irritated tendon moves toward reactive tendinopathy, and eventually toward something that doesn't resolve as quickly.
The window between "this is a warning" and "this is now an injury" is where most spring running injuries happen. And most runners don't recognize they're in it until they've crossed over.
A Safe Ramp-Up Looks Like This
The standard advice to "increase mileage by no more than 10% per week" isn't wrong, but it's incomplete. Here's a more useful framework:
Start from where your tendons are, not where your fitness is. If you took 6–8 weeks mostly off, treat your first two weeks back as genuine base-building even if they feel easy. The goal isn't to get tired. It's to introduce load progressively so your connective tissue has time to respond.
Pay attention to the 24-hour response, not just how you feel mid-run. A tendon that's tolerating load well will feel roughly the same the next morning as it did before your run. Increased stiffness, soreness, or aching in the 12–24 hours after a run is a more reliable signal that you've pushed past your current capacity.
Build in rest days with intention. Tendons need recovery time to remodel. Two hard days back-to-back early in a return-to-run progression doesn't give connective tissue time to adapt between sessions. This is especially relevant for runners over 40, and for women navigating perimenopause, where connective tissue recovery can be slower due to hormonal shifts affecting collagen turnover.
Don't ignore strength. Running places significant eccentric demand on the calf-Achilles complex and the quadriceps-patellar tendon system. If you've been relatively sedentary through winter, the muscles that protect those tendons may also be underprepared. Calf raises, single-leg work, and hip strengthening aren't just injury prevention — they're what allow your tendons to handle increasing load without breaking down.
The Signs Your Tendon Is Telling You to Back Off
Watch for these in the days following a run:
Morning stiffness that takes more than a few minutes to resolve
Pain at the start of a run that doesn't warm up within 5–10 minutes
Tenderness to direct pressure on the tendon itself (not the muscle above it)
Pain that increases over the course of a run rather than settling
Swelling or visible thickening around the tendon
Any of these warrant a modification. Not necessarily a full stop, but a reduction in load and a closer look at what's driving the irritation. A day or two of rest and then returning at lower intensity is a very different outcome than pushing through to a reactive tendinopathy that sidelines you for six weeks.
A Note for Runners Over 40
The basic physiology above applies to everyone, but there are a few additional considerations worth naming for runners in their 40s and beyond — particularly women.
Estrogen plays a meaningful role in collagen synthesis and connective tissue health. As estrogen fluctuates and declines through perimenopause, tendons and ligaments can become less resilient and slower to recover from load. This doesn't mean injury is inevitable. It means the load-management principles above matter even more, and that recovery between sessions deserves more attention than it might have 10 years ago.
If you've noticed that your body is less forgiving of the training approach that used to work fine, that's not a failure of effort. It's physiology. And it's something that can be worked with intentionally, rather than ignored until something breaks down.
When to Get It Looked At
Most tendon irritation responds well to load modification, progressive strengthening, and patience. But some situations are worth getting evaluated sooner rather than later:
Pain that persists beyond a week of reduced training
Symptoms that are getting progressively worse despite backing off
Any history of a prior tendon injury at the same site
Pain significant enough to change your gait mid-run
A physical therapist can assess whether what you're experiencing is early-stage irritation or something that needs a different approach, and can help you modify your training in a way that doesn't require stopping entirely. Most tendon issues don't need rest so much as they need smarter loading.
The Bottom Line
Spring is a genuinely good time to run. The conditions are right, the motivation is high, and there's something real about getting back outside after a long winter. The goal isn't to temper that enthusiasm, but to channel it in a way that gets you through April and May without landing on the injured list.
Respect the timeline your tendons are on. Let your fitness be the ceiling you work toward, not the floor you start from. And if something starts talking to you, listen before it starts shouting.
Dealing With A Spring Running Injury?
Are you dealing with a spring running injury or want to get ahead of one? Book a discovery call to talk through what you’re experiencing and to see if physical therapy is the right path for you.