An Achilles injury is damage to the thick band of tissue that connects your calf muscles to your heel bone. It ranges from mild inflammation and stiffness to a complete tear that can leave you unable to walk. The Achilles tendon is the strongest tendon in the body, capable of handling forces between 1,000 and 5,000 Newtons during activities like running and jumping, but it’s also one of the most commonly injured. Rupture rates have climbed 45% over the past two decades, reaching about 42 per 100,000 people per year.
What the Achilles Tendon Actually Does
Every time you push off the ground to walk, run, or jump, your calf muscles pull on the Achilles tendon, which transfers that force to your heel and propels you forward. It acts like a spring, storing and releasing energy with each step. This is why damage to the tendon affects nearly every movement involving your foot and ankle.
Types of Achilles Injuries
Achilles injuries fall into three main categories, each involving different changes in the tissue itself.
Tendinitis and Peritendinitis
These are acute inflammatory conditions. Tendinitis involves inflammation within the tendon, while peritendinitis affects the sheath surrounding it. Symptoms develop gradually: pain and stiffness around the back of the ankle, typically concentrated about 2 to 6 centimeters above where the tendon attaches to the heel. You might notice a burning sensation, and squeezing the tendon between your fingers often reproduces the pain. A crackling sensation when moving the ankle is common.
Tendinosis
Tendinosis is a chronic degenerative condition, not an inflammatory one, which is an important distinction. Instead of swollen, irritated tissue, the tendon itself breaks down at a structural level. Collagen fibers degrade, scar-like tissue forms, and calcium deposits can develop within the tendon over time. On examination, tendinosis shows up as a thick, nodular cord you can feel through the skin. On ultrasound, affected tendons frequently measure more than 7 mm thick, compared to the normal 4 to 6 mm range. Because there’s no active inflammation driving the problem, treatments that target inflammation alone tend to fall short.
Rupture
A rupture is a partial or complete tear of the tendon. It often happens during sudden explosive movements: pushing off to sprint, pivoting during a basketball game, or landing from a jump. Many people describe hearing a pop or feeling like they’ve been kicked in the back of the leg. A complete rupture makes it nearly impossible to point your toes downward or push off while walking.
Who Gets Injured and Why
Most Achilles ruptures occur in people between ages 30 and 50, with the peak in the 30 to 39 range. Men account for about 82% of all ruptures. The typical profile is a recreational athlete, someone who plays weekend sports without consistent conditioning during the week. The tendon’s blood supply is weakest in that zone a few centimeters above the heel, which makes it vulnerable to both overuse and sudden failure.
Certain medications increase risk significantly. A class of antibiotics called fluoroquinolones (ciprofloxacin is the most well-known) can weaken tendon structure, and about 90% of the tendon injuries linked to these drugs affect the Achilles specifically. If you’ve been prescribed one of these antibiotics and notice new tendon pain, that’s worth flagging to your prescriber immediately.
Other risk factors include carrying excess body weight, running on hard surfaces, wearing worn-out shoes, and ramping up training intensity too quickly. Tight calf muscles and prior tendon problems also raise the odds of a new injury.
How Achilles Injuries Are Diagnosed
For suspected ruptures, clinicians use a simple physical test: with you lying face down, they squeeze your calf muscle and watch whether your foot moves. In a healthy tendon, the foot will point downward. If it doesn’t move, the tendon is likely torn. This test, called the Thompson test, has a sensitivity of 96 to 100% and specificity of 93 to 100% for complete ruptures, making it remarkably accurate without any imaging.
Ultrasound and MRI come into play when the diagnosis is uncertain, when a partial tear is suspected, or when the injury involves chronic tendinosis rather than an acute rupture. Ultrasound can measure tendon thickness precisely and show areas of degeneration, while MRI provides a more detailed picture of the surrounding structures.
Treatment for Tendinitis and Tendinosis
For overuse injuries, the cornerstone of treatment is a structured exercise program rather than rest alone. The most widely used approach involves eccentric heel drops: you rise up on your toes, then slowly lower your heel below the level of a step, loading the tendon in a controlled, lengthening position. The standard protocol calls for two exercises performed 15 times each, twice per day, seven days a week, for approximately 12 weeks. It’s not a quick fix, but this approach has strong evidence behind it for stimulating tendon repair and reducing pain over time.
In the early stages, reducing the load that aggravates your tendon matters. That might mean temporarily cutting back on running mileage, switching to lower-impact activities like cycling or swimming, or using a heel lift in your shoe to take tension off the tendon. Ice after activity can help manage pain, but the real recovery comes from progressively reloading the tendon through exercise.
Treatment for Ruptures
Complete ruptures can be treated with surgery or without it. A large study published in the Journal of Bone and Joint Surgery found no clinically important difference between the two approaches in strength, range of motion, calf circumference, or overall functional scores. Re-rupture rates were similar as well: two in the surgical group and three in the non-operative group. The trend in recent years has shifted toward non-operative treatment with structured rehabilitation for many patients, reserving surgery for competitive athletes or cases where the torn ends of the tendon aren’t well-aligned.
Non-operative treatment typically involves immobilization in a boot with heel wedges, gradually reducing the wedge height over several weeks to bring the foot back to a neutral position. Surgical repair stitches the torn ends together and follows a similar rehabilitation timeline afterward.
Recovery Timeline After a Rupture
Whether treated surgically or conservatively, recovery from an Achilles rupture follows a predictable arc. The first three weeks involve no weight-bearing at all. You’ll use crutches and wear a protective boot or splint. Starting around week four, partial weight-bearing begins, typically increasing by about 25% of your body weight each week until you can walk without crutches.
The middle months focus on restoring range of motion and gradually rebuilding calf strength. Full return to sport generally becomes possible around six months or later, but only after meeting specific benchmarks: completing a progressive running program without pain or swelling, and demonstrating at least 90% of the strength and function of your uninjured side on standardized tests. Rushing this timeline is one of the most common mistakes, and it raises the risk of re-injury.
Reducing Your Risk
Consistent calf strengthening is the single most effective preventive measure. Eccentric exercises, the same ones used to treat tendinosis, also help protect a healthy tendon by improving its ability to handle load. Warming up before explosive activities matters more for the Achilles than for most other structures, because the tendon is stiffer when cold and more prone to sudden failure.
If you’re a weekend athlete, bridging the gap between sedentary weekdays and intense weekend play makes a real difference. Even two or three short sessions of calf raises and light jogging during the week can keep the tendon conditioned. Replacing running shoes before they lose their cushioning, gradually increasing training volume rather than jumping up suddenly, and addressing tight calves through regular stretching all contribute to long-term tendon health.