You felt it first as a little stiffness coming down off Green Mountain. Nothing dramatic. The next morning the first few steps out of bed were sore, and by the time you got to the kitchen it had loosened up enough that you talked yourself out of worrying. Three weeks later you are still running, still sore in the morning, and the tendon is starting to look a little thicker than the other side.
That pattern is one of the most common things we see in runners around Wheat Ridge and the foothills. It is also one of the most commonly mislabeled. Most people call it Achilles tendinitis. By the time the morning stiffness has been around for a month or more, it is often something a little different, and the difference changes what actually helps.
Tendinitis and tendinosis are not the same problem
Tendinitis is an irritated, inflamed tendon. It usually shows up fairly quickly after a change in training, and it tends to behave like an inflammatory problem: warm, tender, reactive, and often settling down over a few weeks when the load comes off.
Tendinosis is a degenerative change in the tendon itself. The collagen fibers lose their tidy parallel organization, the tendon thickens, and new blood vessels grow into tissue that is normally fairly bloodless. There is not much active inflammation left to calm down. That is the part that trips people up.
Why it matters in practical terms:
- Rest alone behaves differently. A reactive tendon often quiets with relative rest. A degenerative tendon frequently feels better while resting and then hurts again the moment you return, because nothing about the tissue changed.
- Anti-inflammatories do less. If there is little inflammation driving the pain, an anti-inflammatory may take the edge off without moving the underlying problem.
- Loading becomes the treatment, not the enemy. Current guidance generally favors progressive, carefully dosed tendon loading for degenerative Achilles problems rather than extended rest.
- The timeline is longer. Many patients with a reactive tendon turn the corner in several weeks. Long-standing tendinopathy often takes a few months of consistent work.
In real life the two overlap. A degenerative tendon can have a reactive flare on top of it, which is usually what brings someone in. The useful question is not which single label applies, but how much of each is going on right now.
Where the pain sits changes the plan
There are two common locations, and they do not respond to the same things.
Midportion pain
Tenderness sits in the tendon itself, roughly two to six centimeters above the heel bone. This is the more common presentation in runners and generally the more cooperative one. Loading programs tend to be well tolerated here, including work through a full ankle range.
Insertional pain
Tenderness sits right where the tendon attaches to the back of the heel. This one is pickier. Deep stretching and dropping the heel below level often aggravate it, because that position compresses the tendon against the bone. Plans here usually limit that end range early, and a small heel lift in your shoes sometimes buys enough relief to let the rehab work happen.
If you have been doing eccentric heel drops off a stair for six weeks and feel worse, insertional pain is a reasonable thing to ask about. It is a common mismatch between a good exercise and the wrong location.
What trail running does to the Achilles
Trails ask more of this tendon than a flat road does, in a few specific ways.
- Sustained climbing keeps the ankle in dorsiflexion under load, which lengthens the calf and tendon repeatedly over long stretches.
- Uneven footing means the tendon absorbs loads it did not plan for, at angles it did not plan for.
- Descending loads the calf and Achilles eccentrically, mile after mile, and that is usually where people notice the pain first.
- Shoe changes matter more than people expect. Moving from a higher heel-to-toe drop to a lower one shifts load onto the Achilles, and doing that at the same time you add vert is a common setup for trouble.
Along the Front Range there is a seasonal version of this too. People who ran flat pavement all summer start adding foothills trails in the fall, and the calf complex gets a new job on short notice.
What an evaluation actually looks like
A good Achilles visit is not just a poke at the sore spot. It generally includes:
- Locating the pain precisely, because midportion and insertional problems go different directions.
- Testing calf strength and endurance, often by comparing single-leg heel raises side to side. A deficit here is common and very fixable.
- Checking ankle range and great toe mobility, since stiffness up or down the chain changes how the tendon is loaded.
- Looking further up the leg at hip and calf mechanics, because the Achilles is often the place that complains about a problem created elsewhere.
- Imaging only when it will change something.
On that last point, an ultrasound probe at the bedside can show tendon thickening, the disorganized tissue typical of tendinosis, partial tears and full ruptures, and it can do it while you are sitting there. Our page on Achilles tendinitis and tears walks through what that evaluation covers, and this is the same reason an MRI is often unnecessary for a tendon question. We wrote more about that tradeoff in what in-office ultrasound can show you right away.
What treatment usually involves
Plans vary, and yours should be built around your exam rather than a template. That said, most Achilles tendinopathy plans share the same backbone:
- Adjust load without stopping entirely. Usually that means cutting vert and speed work first, keeping easy running if it does not increase symptoms, and watching how the tendon behaves the next morning rather than during the run.
- Start a progressive calf and tendon loading program. Slow, heavy, and consistent beats hard and sporadic. This is the part that changes the tissue, and it is also the part people abandon early because progress is gradual.
- Address the setup. Shoe drop, training progression, calf strength deficits, hip mechanics. Fixing the tendon without fixing the reason it got overloaded tends to buy a recurrence.
- Add targeted options when the basics stall. Depending on what the exam and ultrasound show, that conversation can include bracing or heel lifts, specific manual techniques, or an image-guided procedure. Not everyone needs these, and they work best layered on top of loading rather than instead of it.
- Return to trails in stages. Flat before rolling, rolling before sustained climbing, and descending added deliberately rather than on the first good-weather weekend.
If you want a sense of how the options stack up before anyone talks about surgery, our post on the non-surgical ladder for joint pain lays out the same general approach we use here.
What tends to slow people down
- Waiting for it to be pain free before loading it. Mild, settling discomfort during rehab is often acceptable. Pain that climbs and lingers into the next day is the signal to back off.
- Stretching an insertional problem aggressively. This is the single most common thing we ask people to stop doing.
- Stopping the program once it feels better. The tendon usually needs the work longer than the symptoms last.
- Changing three things at once. New shoes, new mileage, new terrain in the same week makes it impossible to tell what helped.
When not to wait it out
Some Achilles problems need to be looked at promptly rather than managed at home. Get evaluated soon if you have:
- A sudden pop or snap at the back of the ankle, often with the feeling of being kicked
- Real weakness pushing off, or trouble rising onto your toes on that leg
- A visible gap or dent in the tendon
- Pain that is not improving at all after several weeks of sensible management
A suspected rupture should be evaluated within days, not weeks. If you also have fever, significant redness and swelling spreading up the leg, calf pain with swelling that came on without an obvious injury, or numbness and loss of function in the foot, that belongs in urgent care or the emergency department rather than a routine clinic visit.
Getting it looked at
Dr. Christopher Kroner is a family practice and sports medicine physician who has worked everywhere from professional and Olympic athletes to high school sidelines, and Achilles problems in recreational runners are routine here. Sports medicine visits are included in a primary care membership and are also available as a standalone visit if your primary care is somewhere else. A direct primary care membership is not health insurance.
If your Achilles has been nagging you through more than a few weeks of trail miles, a visit with enough time to actually examine the tendon and build a plan is usually worth more than another month of guessing. You can book a free 30-minute meet and greet with Dr. Kroner or call 720-807-9961. We are at 4045 Wadsworth Blvd #300, Wheat Ridge, CO 80033, open Monday through Friday, and we see patients from Arvada, Lakewood, Golden, Edgewater and west Denver.
This article is for educational purposes only and is not a substitute for individual medical advice. Please see our medical disclaimer.