What Is an Achilles Injury? Types, Causes & Treatment

An Achilles injury is any damage to the thick band of tissue that connects your calf muscles to your heel bone, ranging from chronic irritation and microscopic fiber breakdown to a full-blown rupture that snaps the tendon apart. The Achilles tendon is the largest and strongest tendon in the body, yet it is also one of the most frequently injured, in part because its middle section receives a surprisingly poor blood supply. Understanding the different types of Achilles injuries matters because a nagging ache at the back of your heel and a sudden pop during a basketball game are fundamentally different problems with different treatment paths.

Why the Achilles Tendon Is Vulnerable

Your Achilles tendon handles enormous forces every day. During ordinary walking, it stretches about three percent of its length; during fast running that strain roughly doubles, and a maximal hop landing pushes it close to nine percent.

Despite bearing these loads, the tendon has a built-in weak spot. Anatomical studies have identified three distinct blood-supply zones along its length. The sections closest to the calf muscle and closest to the heel bone are fed by the posterior tibial artery, but the middle portion relies on a different vessel, the peroneal artery, and receives far less blood flow overall.¹ That relatively starved midsection is exactly where most ruptures and many overuse injuries occur. Less blood means slower delivery of oxygen and repair cells, so micro-damage accumulates faster than the tendon can fix it.

From an evolutionary standpoint, the Achilles tendon’s length and elasticity are features, not bugs. The tendon stores and releases elastic energy during each stride, allowing your calf muscles to work over shorter ranges and at lower effort. The prevailing evidence suggests the human Achilles evolved primarily to reduce the energy cost of walking and running rather than to maximize explosive power.² That spring-like design is efficient, but it also means the tendon is routinely loaded near its mechanical limits.

Types of Achilles Injuries

Not all Achilles problems are the same, and the location of the injury along the tendon often determines both the symptoms and the treatment approach.

Midportion Tendinopathy

This is the most common Achilles complaint, especially among runners and recreational athletes. It involves degeneration and disorganization of the tendon fibers in that poorly vascularized middle zone, typically two to six centimeters above the heel. You feel a stiff, achy pain that warms up with activity but worsens afterward. The tendon may look visibly thickened or feel lumpy to the touch. It is not an inflammatory condition in the traditional sense; the tissue changes are more degenerative than inflamed, which is why “tendinopathy” has largely replaced the older term “tendinitis” in clinical use.

Insertional Tendinopathy

Here the damage sits right where the tendon meets the heel bone. It often involves calcification within the tendon and a bony prominence on the back of the heel called a Haglund’s deformity. In one surgical study, roughly three-quarters of patients with insertional Achilles tendinopathy had calcification visible on imaging, with an average calcified deposit over a centimeter long.³ A separate matched-cohort analysis confirmed that patients with insertional disease show more prominent bony changes at the heel and higher rates of intratendinous calcification compared with controls.⁴ Insertional tendinopathy can be particularly stubborn because the bone-tendon junction is hard to offload during daily life, and shoes that press on the back of the heel constantly aggravate it.

Partial and Complete Ruptures

A partial tear means some but not all of the tendon fibers have torn. You may feel a sharp pain or a sensation that someone kicked the back of your leg, but you can still walk, albeit with difficulty. A complete rupture is unmistakable: a sudden pop, immediate weakness, and an inability to push off with that foot. Video analysis of professional athletes who ruptured their Achilles found that over eighty percent of cases were non-contact injuries. The ankle was typically bending upward (dorsiflexion) with the body leaning forward, and roughly four in five ruptures happened during either a takeoff or acceleration move or a stop-and-turn maneuver.⁵

Causes and Risk Factors

Most Achilles injuries stem from some combination of excessive or poorly managed mechanical load and underlying tissue vulnerability. A review of the research identified both factors you cannot change and ones you can: genetic predisposition, anatomical variations, sex, and age are non-modifiable, while nutrition, training errors, and failure to monitor tendon health are modifiable.⁶ Weekend warriors who ramp up activity abruptly are classic candidates, but so are sedentary adults who suddenly sprint after a bus.

Diabetes deserves special mention. People with diabetes often develop structural changes in the Achilles even before symptoms appear, including thickening, disorganized collagen, and calcification where the tendon meets bone. At a microscopic level, sugar molecules attach to collagen fibers and stiffen the tissue, reducing its ability to slide and absorb load.⁷ Diabetic tendons also heal more slowly after injury.

Certain medications raise the risk, too. Fluoroquinolone antibiotics (drugs like ciprofloxacin and levofloxacin) have a well-documented association with tendon injury. A meta-analysis confirmed the link and flagged older age and corticosteroid use as additional risk amplifiers.⁸ A population-based study put numbers on it: current fluoroquinolone use roughly tripled the risk of Achilles tendon rupture, and taking a fluoroquinolone alongside an oral corticosteroid raised the risk nearly twentyfold.⁹ If you are on either of these medications and notice heel or ankle pain, bring it up with your prescriber.

How Achilles Injuries Are Diagnosed

For a complete rupture, the diagnosis is largely clinical. Three bedside findings — a gap you can feel in the tendon, weakness when trying to rise onto your toes, and an abnormal squeeze test (where squeezing the calf fails to move the foot) — identified every surgically confirmed complete rupture in one study with perfect sensitivity. MRI, by contrast, was read as a partial tear or inconclusive in about one in ten of those same cases.¹⁰ A newer clinical test, the STAMP test (Simmonds-Thompson Achilles Mismatch Protocol), showed strong sensitivity for both acute and chronic ruptures and may catch cases the traditional Thompson squeeze test misses, particularly in delayed presentations.¹¹

For tendinopathy, imaging plays a bigger role because the tendon is intact and the question is how much structural change has occurred. Both ultrasound and MRI can identify abnormal morphology, but neither is dramatically superior. One prospective comparison found that ultrasound and MRI showed roughly similar diagnostic accuracy for both insertional and midportion Achilles tendinopathy, with no significant difference favoring one modality over the other.¹² An older two-year study found that graded MRI findings were better correlated with how patients were doing twelve months later, while ultrasound findings were not.¹³ In practice, ultrasound is often the first choice because it is cheaper, faster, and lets the clinician watch the tendon move in real time. MRI is typically reserved for cases where the clinical picture is unclear or surgery is being planned.

Conservative Treatment for Tendinopathy

The cornerstone of treating Achilles tendinopathy without surgery is exercise-based rehabilitation, specifically loading the tendon in a controlled, progressive way. Eccentric exercises, where you slowly lower your heel off the edge of a step, have the strongest track record. A narrative review of seven studies found that every one reported significant improvements in pain, and all six that measured function found significant gains.¹⁴ When eccentric exercise was compared with doing nothing, it won clearly. But when compared with other active treatments or multimodal programs, the advantage was less definitive.

The traditional Alfredson protocol asks for 180 repetitions per day (three sets of fifteen, twice daily, on both bent and straight knee). That volume can feel overwhelming, and there is evidence that a less rigid approach works just as well. A randomized trial compared the standard 180-rep protocol with a “do as tolerated” version and found no significant difference in pain or function scores by week six.¹⁵ That matters for adherence: a program you actually complete beats a perfect one you abandon.

Beyond eccentric loading, many clinicians add heavy slow resistance training, isometric holds for pain relief, and gradual return to sport-specific loading. Shoe modifications, temporary heel lifts, and activity management round out the conservative toolkit. The key message is that tendons respond to load, not rest. Prolonged immobilization tends to make tendinopathy worse.

Surgery Versus Rehabilitation for Ruptures

For decades, surgical repair was considered the default treatment for a complete Achilles rupture, particularly in active people. That consensus has shifted considerably. A meta-analysis of randomized trials found that when early functional rehabilitation with range-of-motion exercises was used, rerupture rates were statistically equal between surgical and non-surgical patients. Surgery only showed a clear advantage in preventing re-rupture when early rehabilitation was not employed.¹⁶ At the same time, surgery carried a roughly sixteen-percentage-point higher rate of other complications, and there was no significant difference in calf strength or functional outcome scores between the groups.

More recent data confirms this overall picture while adding nuance. A 2025 review reported that surgery reduces the absolute rerupture rate modestly (about two percent versus four percent for non-surgical care) and gets people back to work about nineteen days sooner on average. But it also increases the complication rate: wound infections after open repair occur in about six percent of cases, and deep vein thrombosis in about one percent.¹⁷ The emerging view is that the quality of the rehabilitation protocol matters more than whether or not you have surgery. Early weight-bearing and progressive loading, whether post-operative or non-operative, are what drive good outcomes.¹⁸

When Surgery Happens, What Does It Look Like

If surgery is chosen, the options fall along a spectrum from fully open to minimally invasive. An open repair uses a larger incision (around ten centimeters) to directly visualize the torn ends and stitch them together. Percutaneous and minimally invasive techniques use smaller incisions and specialized instruments to pass sutures through the tendon with less soft-tissue disruption.¹⁹

A meta-analysis of randomized trials comparing open repair with minimally invasive repair found no significant difference in functional scores or rerupture rates. Minimally invasive surgery took about twenty minutes less in the operating room and had a significantly lower rate of superficial infection (under one percent versus about six percent for open). The trade-off was a higher rate of sural nerve injury — the small sensory nerve that runs near the Achilles — at roughly three percent in the minimally invasive group versus essentially zero for open repair, where the nerve can be directly visualized and protected.²⁰

A biomechanical concern with minimally invasive repairs is early elongation. In a cadaver study, open repair showed about half the tendon stretching after repetitive loading compared with several minimally invasive techniques, though ultimate failure strength was comparable across all methods.²¹ Whether that extra early stretch translates into meaningful functional differences in living patients remains debated. Surgeons weigh infection risk, nerve injury risk, and tendon-length preservation when choosing a technique, and the best option often depends on the individual tear pattern and the surgeon’s experience.

Return to Sport After Rupture

For competitive athletes, the bottom line question is often how quickly and how fully they can get back on the field. A study of elite athletes who underwent a specific surgical repair technique found a mean return-to-play time of about twenty-two weeks, with nearly all athletes returning to their original sport within seven months.²² Those are encouraging numbers, but they come from a selected group with elite-level rehab support. For recreational athletes and everyday exercisers, timelines tend to be longer and the return less complete, particularly for activities that require maximal sprinting or jumping.

Performance often does not return to one hundred percent. Even after a successful repair and diligent rehab, many people report persistent deficits in explosive push-off strength on the injured side. The calf on the injured leg may remain smaller. These are realities that are worth discussing early with your treatment team rather than discovering months into recovery.

Platelet-Rich Plasma and Shockwave Therapy

Platelet-rich plasma (PRP) injections, where a concentrated portion of your own blood is injected into the injured tendon, have generated a lot of interest but only moderate evidence. A systematic review found that lower-quality studies tended to favor PRP while the stronger evidence did not support a significant benefit.²³ Improvement in symptom scores was reported, but well-designed randomized trials are still needed to confirm whether PRP adds anything on top of a good exercise program.

Extracorporeal shockwave therapy (ESWT), which delivers focused sound-wave pulses to the tendon, is another option, particularly for insertional tendinopathy. A retrospective comparison found both ESWT and PRP produced significant improvements in pain and function scores over six months, with patient satisfaction exceeding seventy percent in both groups and no meaningful difference between them at most time points.²⁴ Neither therapy is a magic bullet, but both are generally safe and can be useful adjuncts when exercise alone is not enough.

Achilles Problems in Children and Adolescents

Kids rarely rupture their Achilles tendon, but they do get a related condition that can mimic one. Sever’s disease (calcaneal apophysitis) is irritation of the growth plate at the back of the heel, right where the Achilles tendon attaches. Because the heel’s growth plate does not close until at least age fourteen, the repetitive pulling of the Achilles during running and jumping sports creates stress on bone that is still forming.²⁵ It is one of the most common causes of heel pain in active children between about eight and fourteen years old. Treatment is straightforward: activity modification, stretching, supportive footwear, and patience. The condition resolves on its own once the growth plate matures.

Sever’s disease is worth mentioning here because parents often worry that their child has “an Achilles injury” when the tendon itself is healthy. The pain is at the heel, worsened by activity, and sometimes made worse by cleats or flat shoes. Knowing this is a growth-related overuse issue, not a tendon tear, avoids unnecessary imaging and anxiety.

The Psychological Side of Achilles Pain

Chronic Achilles tendinopathy is sometimes dismissed as a simple overuse injury that should resolve with rest, but for some people it becomes a frustrating, long-lasting condition. One recent study looked at whether prolonged symptoms might lead to a phenomenon called central sensitization, where the nervous system amplifies pain signals regardless of what is happening in the tendon itself. Interestingly, it found that how long someone had been symptomatic did not correlate with sensitization scores. Only about five percent of patients with midportion Achilles tendinopathy met the clinical threshold for central sensitization, and all of them were women. However, worse symptom severity and higher pain intensity did track with higher sensitization scores.²⁶

The practical takeaway is that for most people with chronic Achilles pain, the problem remains local rather than a sign that their entire pain system has gone haywire. But for the small subset whose pain seems disproportionate to the structural findings, screening for sensitization may help guide treatment toward strategies that address the nervous system as well as the tendon. Clinicians increasingly recognize that ignoring the psychological and neurological dimensions of tendon pain can stall recovery just as much as ignoring the mechanical ones.