⏵ Body, mind & recovery

Injury Playbook: Knee, IT Band, and Achilles for Ultra Runners

Three injuries end more ultra seasons than anything else: runner’s knee (pain at the front of the kneecap), IT band syndrome (sharp pain on the outside of the knee), and Achilles tendinopathy (a sore, stiff tendon at the back of the ankle). The runners who beat them do two things: they catch the warning signs early instead of training through a small ache until it is a big one, and they come back on a controlled progression instead of jumping straight back to where they got hurt. This is the playbook for each one: how to spot it, what the rehab that actually has evidence behind it looks like, how long it really takes, and how to return to running without re-injuring.

⏵ On this page

The big three, at a glance

Here is the short version before we go deep. The knee is the single biggest trouble spot in running, close to half of all injuries, and runner’s knee and IT band are the top two complaints there. The Achilles is the tendon most likely to flare up once you stack on the vert. The prevalence numbers below come from systematic reviews of runners and jump around a lot by study, so read them as ballpark, not gospel.

Injury	Where it hits	How common	Earliest sign	What fixes it
Runner’s knee (patellofemoral pain)	Front of / around the kneecap	Around the most common running injury overall; reported prevalence roughly 7% to 17%, and the knee is close to half of all running injuries	A dull ache around or behind the kneecap on long descents, stairs, and after you sit a while	Hip plus quad strength, a small cadence bump, and dialing back downhill volume while it settles
IT band syndrome	Outside of the knee (sometimes the hip)	About 8% of running injuries; one of the top two knee complaints behind runner’s knee	A sharp, burning pain on the outside of the knee that shows up at a predictable distance and is worse downhill	Hip abductor and glute strength, a relative-rest reset, and gait tweaks (a slightly quicker cadence)
Achilles tendinopathy	The tendon at the back of the ankle / lower calf	Among the highest-incidence running injuries (around 10% of new injuries); prevalence roughly 6% to 9%	Morning stiffness and a tender, sometimes thickened spot on the tendon that warms up then aches again after	Progressive calf loading (heavy-slow or eccentric heel drops), patience, and a slow return-to-run

For the prevention side of this (the weekly strength plan and how to ramp mileage so you do not get here in the first place), see our strength and injury-prevention guide. This page is the playbook for when something already hurts.

Catch it early: read the warning signs

Almost every overuse injury whispers before it screams. The whole game is hearing the whisper. A small ache that shows up at the same point every run, a stiffness that takes longer to warm up each week, a spot that is tender to the touch the morning after a hard descent. That is the window where two easy weeks fixes it. Train through it for a month and you are looking at two lost months instead.

The pattern that means back off now

Watch for pain that is getting more predictable, not less. A niggle that used to come and go but now shows up at the same mile, every time, is a tissue telling you it is overloaded. So is a warm-up that keeps getting longer, or soreness that lingers into the next morning instead of clearing overnight. Add in a recent spike (a big jump in weekly mileage, a new pile of downhill, fresh shoes, a hard block with no easy week) and you have the classic setup for all three of these.

When you catch that pattern, you do not have to stop dead. You back off the thing that is loading it: cut the downhills for runner’s knee and IT band, cut the hard calf-pounding climbs and speed for Achilles, drop your volume 20 to 30 percent for a week or two, and start the targeted strength work below. Caught at the whisper stage, most of these never become a real injury at all.

Runner’s knee (patellofemoral pain)

This is the most common running injury there is, and on long mountain days the descents are what bring it out. It is a dull ache around or behind the kneecap that flares on downhills, stairs, squats, and after you sit for a while. It is rarely a true structural problem. Most of the time it is a load-and-control problem, which is good news, because that is fixable.

Why it happens, and what actually helps

The kneecap rides in a groove, and when your hip and quad cannot control your leg well, especially as you fatigue late in a long run, the knee caves slightly inward and the kneecap tracks badly and gets cranky. So the fix is not babying the knee, it is making the stuff above and around it stronger. The evidence here is pretty clear: adding hip strength (glute med and hip abductors) to quad strength beats quad work alone, with people getting out of pain faster and stronger. Single-leg squats, step-downs, side planks, and banded lateral walks are the bread and butter.

Alongside the strength, two simple tweaks take load off the joint right away. Bump your cadence up about 5 to 10 percent so you stop overstriding (one study found roughly a 10 percent step-rate increase cut patellofemoral joint force by up to about 20 percent). And control your downhills: shorter, quicker, quieter steps instead of long braking lunges that hammer the kneecap. Cut your downhill volume while it is angry, keep running the flats and gentle climbs if they are pain-free, and give it a few weeks.

IT band syndrome

IT band is the cruel one, because it often feels totally fine until a switch flips. You will be cruising along and then a sharp, burning pain lights up on the outside of the knee, usually at a pretty predictable distance, and it is worse going downhill. Once it is truly fired up it will stop you, and pushing through just keeps it lit. This one needs a smarter approach than grinding.

It is a hip problem wearing a knee disguise

For years people blamed friction and attacked the band itself with foam rollers and stretching. The newer understanding is that the IT band is barely stretchable tissue, and the real driver is usually compression at the knee from poor hip control: weak hip abductors and glutes let your pelvis drop and your thigh rotate in, which jams that tissue against the bone. So rolling the band feels like something but does not fix the cause. Hip abductor and glute strength does. Across the research, hip strengthening programs cut IT band pain meaningfully over about 2 to 8 weeks.

The other half is a real reset. Unlike a grumpy Achilles, a truly angry IT band usually wants a short stretch of relative rest, days to a couple of weeks of cutting way back or cross-training, while you load the hips and let it calm down. Then return gradually, flats first and downhills last, since descents are what light it up. A small cadence increase helps here too, for the same reason it helps the knee: less hip drop, less time crashing onto a long stride. Returning too aggressively is the number one reason it bounces straight back.

Achilles tendinopathy

All those climbs you love are exactly what loads the Achilles, so trail and ultra runners see a lot of this. It starts as morning stiffness and a tender, sometimes thickened spot on the tendon that warms up as you run and then aches again after. The thing to know: the tendon does not want rest, it wants the right kind of load. This is the injury with the most specific, best-tested rehab on the page.

Phase	What you do	Rough dose
Isometrics (most painful, early)	Hold a calf-raise position (two legs, or assisted) to calm the tendon and load it without movement	5 holds of 30 to 45 sec, once or twice a day, when even heel drops hurt
Heavy-slow or eccentric loading (the engine)	Slow heel raises and lowers, both straight-knee and bent-knee, building load over weeks. Eccentric heel drops (Alfredson) and heavy-slow resistance both have strong evidence	Eccentric: 3 x 15 each, twice daily. Heavy-slow: ~3 to 4 sets of 6 to 8 heavy reps, every other day. Run a 12-week block
Energy storage / plyometric	Add hops, skips, and faster calf work once the slow stuff is pain-free, so the tendon can take running again	Start only after 4 to 6 weeks of pain-free loading and 20+ single-leg calf raises without pain

Two loading styles have the strongest evidence and both work: the classic Alfredson eccentric heel drops (3 sets of 15, twice a day, for 12 weeks, which improved most people in the original trial) and heavy-slow resistance (fewer, heavier reps every other day), which tends to be better tolerated for similar results. Pick one, keep pain at or below about 3 out of 10 and no worse the next morning, and give it the full 12 weeks. This is a guide, not a prescription.

Load the tendon, do not baby it

The instinct to fully rest a sore Achilles is understandable and usually wrong. Tendons remodel in response to load, and going completely soft just leaves you with a weak, cranky tendon that flares the moment you run again. The job is to load it heavily but slowly and within tolerable pain, building capacity over weeks. You can usually keep running at a reduced level the whole time as long as you respect the pain rule, the tendon settles by the next morning, and you hold off on the calf-hammering stuff (steep climbs, fast running, hills) until it is ready.

Be honest about the timeline. A structured calf-loading block is about 12 weeks, and a meaningful case can take 3 to 6 months to feel truly solid. You earn speed and hills back only after the slow loading is pain-free and you can do 20 single-leg calf raises without symptoms. If you have given it 12 honest weeks of well-dosed work and you are stuck, or the pain is high and not budging, that is your cue to see a sports physio rather than keep guessing.

Return to running without re-injuring

This is the part people botch. They feel good for a week, jump back to their old long run, and re-tear the thing they just spent two months fixing. The way back is a graded progression where you add one variable at a time and let the tissue prove it can handle each step before you take the next. Here is a conservative version that works for all three.

Stage	The session	Green light to move on
Stage 1	Walk / run intervals on flat, soft ground: 1 min run, 1 to 2 min walk, total 20 to 30 min, every other day	Pain stays at or below 3/10 during, and back to normal by the next morning
Stage 2	Lengthen the run intervals (2 to 5 min run), shrink the walks, keep it flat and easy	No next-morning flare, no limp, no swelling. Hold the week if any of those show up
Stage 3	Continuous easy running, then add back gentle rolling terrain. Keep it short	Add time before you add intensity or hills. One variable at a time
Stage 4	Reintroduce real downhills, then quality. Downhills last for knee and IT band, speed last for Achilles	Build the long run and the vert in steps, never in one big jump past your recent longest

The order matters: time before intensity, flats before hills, downhills and speed last. For runner’s knee and IT band, descents are the final thing you add back. For Achilles, fast running and steep climbs come last. And whatever you do, do not let your first big long run leap far past your recent longest, that single-run spike is what re-injures people. Grow it in steps.

Run through it, or stop? The pain rule

You do not have to fully rest every twinge, and you should not push through everything either. There is a simple, evidence-backed rule that keeps you on the right side of it. It is the same traffic-light model physios use to let people keep training through tendon rehab.

The traffic-light pain model

Rate the pain 0 to 10 during the run, right after, and the next morning. At or below about 3 out of 10, not getting worse as the run goes on, and back to your normal baseline by the next morning: green light, you can keep loading it gently, and for tendons that load is actually part of the cure. Creeping up toward 5, or still sore the next morning: yellow, hold your volume where it is and do not add anything. Sharp, climbing past 5, making you limp or change your stride, or still flared a day later: red, back off and reassess.

A few things override the traffic light entirely. Sharp, pinpoint pain over bone that sharpens when you run and does not warm up is a red flag for a bone stress injury, and that one you stop and get imaged, because running through it can turn a stress reaction into a full fracture. A knee that swells, locks, catches, or gives way is not a typical overuse niggle either. When in doubt, or when honest rehab is not moving after several weeks, see a sports physiotherapist or physician. That is not giving up, that is how you save your season.

⏵ Catch the spike before it catches you

Nearly every one of these injuries traces back to one thing: you loaded faster than your body could adapt. Summit Line builds a plan around your real fitness and schedules strength alongside it, and its load-aware Build Watch (acute-to-chronic load) flags when your mileage or vert is ramping faster than you can take, the exact spike that sets off runner’s knee, IT band, and Achilles. Train against your real load, not a static chart.

Get started free →See the load watch in the demo

⏵ Free calculators

A lot of injury prevention is just pacing the descents honestly and not overcooking the early miles. Run your numbers with our free, no-signup tools.

See all free running tools →

⏵ Keep reading

Related Summit Line guides

Ultra running injury FAQ

What are the most common injuries for ultra and trail runners?

Most ultra injuries are overuse, not crashes, and three show up over and over: runner’s knee (patellofemoral pain) around the front of the kneecap, IT band syndrome on the outside of the knee, and Achilles tendinopathy at the back of the ankle. The knee alone is close to half of all running injuries, with runner’s knee and IT band the top two complaints there. Achilles tendinopathy is one of the highest-incidence injuries in runners, especially once you add a lot of climbing. Plantar fasciitis and bone stress injuries round out the list. The thread through all of them is the same: you loaded the tissue faster than it could adapt, which is exactly what catching it early and a controlled return guard against.

How do I know if it’s runner’s knee or IT band syndrome?

Location and timing usually tell them apart. Runner’s knee is a dull, achy pain at the front of or behind the kneecap that comes on with descents, stairs, squatting, and after you have been sitting a while (the so-called theater sign). IT band syndrome is a sharper, more burning pain on the outside of the knee that tends to switch on at a fairly predictable point in a run and gets worse going downhill. Runner’s knee is diffuse and hard to point to; IT band you can often poke right on the sore spot. Both are driven a lot by weak or sleepy hips and by mileage or downhill spikes. If you genuinely cannot tell, or the knee swells, locks, or gives way, get it looked at rather than guessing.

How long does it take to recover from Achilles tendinopathy?

Longer than you want, and rushing it is how it comes back. Tendons remodel slowly, so plan on a structured loading program of about 12 weeks, and know that meaningful cases can take 3 to 6 months to feel solid again. The good news is you usually do not have to stop running completely. The evidence-backed approach is progressive calf loading (heavy-slow resistance or eccentric heel drops, both work, with heavy-slow often better tolerated) while keeping pain at or below about 3 out of 10 and no worse the next morning. You earn the right to add hops and speed once you can do 20 single-leg calf raises pain-free and have strung together several weeks of pain-free loading. If 12 weeks of honest, well-dosed work gets you nowhere, see a sports physio.

Should I keep running through knee, IT band, or Achilles pain?

It depends on the tissue and how loud it is, and this is one of the most important calls in ultra running. Tendon and muscle pain (Achilles, and a lot of runner’s knee) will often warm up and is usually fine to load gently as long as it stays at or below about 3 out of 10, does not get worse as the run goes on, and is back to baseline the next morning. Tendons actually need load to heal, so total rest is often the wrong move there. IT band tends to need a short relative-rest reset because once it is truly fired up, running through it just keeps it angry. And any sharp, pinpoint, gets-worse-as-you-run pain, especially over bone, or a knee that swells, locks, or buckles, means stop and get it checked. Sore and stiff you can usually work with. Sharp, swollen, or worsening you do not.

What strength work actually prevents these injuries?

Hips and calves do most of the heavy lifting. For runner’s knee and IT band, the strongest evidence is on hip strength: glute med and hip abductor work (side planks, banded walks, single-leg squats and step-downs) added to quad work beats quad work alone for cutting pain and getting you back faster. Weak, lazy hips let your knee cave inward on every step, which loads both the kneecap and the IT band. For Achilles, it is direct calf capacity: heavy straight-knee and bent-knee calf raises build the tendon’s tolerance for thousands of loaded foot strikes. Two strength sessions a week, kept up year round, is enough to get and hold the benefit. Pair that with a controlled mileage ramp and real downhill prep and you have covered most of what hurts ultra runners.

Will changing my running cadence help my knee or IT band?

It can, and it is one of the lowest-risk things to try. Bumping your step rate up by about 5 to 10 percent shortens your stride, lands your foot closer under your body, and meaningfully cuts the load through the knee. Studies have found roughly a 10 percent cadence increase can drop patellofemoral joint force by up to about 20 percent and reduce the hip-drop and impact that feed IT band syndrome, with pain and function improving and holding for months. It is not a magic fix and the evidence is not unanimous, so treat it as one tool alongside the strength work, not a replacement for it. The practical move: check your current cadence, nudge it up about 5 percent, hold it on easy runs until it feels natural, then reassess.

This guide is for training and educational purposes and reflects current sport-science consensus and reputable rehab and coaching practice. It is not medical advice and it is not a diagnosis. The prevalence numbers come from published reviews and surveys of runners and vary a lot by study, and the loading doses are general starting points, not a prescription for your specific case. If you have pain that is sharp, focal (especially over bone), swelling a joint, or simply not improving after a few weeks of sensible rehab, see a sports physiotherapist or physician before you keep training.