Achilles Rupture

Your Achilles is the rope-like tendon at the back of your ankle — the largest and strongest tendon in the body, formed by the two big calf muscles (the gastrocnemius and the soleus) merging together and inserting onto the back of your heel bone (the calcaneus). When you push off the ground to walk, run, or jump, that tendon is doing the work.

An Achilles rupture is when the tendon snaps clean through. It almost always happens in a specific spot — about 2 to 6 centimeters above where the tendon meets the heel — because that zone has the worst blood supply along the whole tendon (surgeons call it the watershed zone). The mechanism is a sudden, forceful push-off: starting a sprint, jumping for a rebound, lunging in tennis, sometimes just stepping awkwardly off a curb. Most patients describe a sharp, audible pop and the unmistakable feeling of being kicked or shot in the back of the leg — often turning around expecting to find someone behind them. Walking flat is then possible but pushing off the toe is not.

The classic patient is a deconditioned man in his 30s, 40s, or 50s returning to a sport after a layoff — the so-called weekend warrior. Two specific risk factors stand out: prior steroid injections directly into the tendon (which is why we don't put cortisone into the Achilles), and a recent course of fluoroquinolone antibiotics like ciprofloxacin or levofloxacin, both of which weaken the tendon's collagen.

The injury announces itself: a sudden, loud pop and a sharp pain at the back of the leg, mid-calf to just above the heel. Many patients try to keep playing the next point and find they can walk flat-footed but have lost the ability to rise up onto the toes of that foot. Within a few hours the back of the ankle swells and bruises, and a small valley or gap can often be felt above the heel where the two ends of the torn tendon have retracted apart. The pain itself can be surprisingly modest after the first few minutes — it's the loss of push-off, not the pain, that usually drives the trip in.

What's not typical: a slow, gradually worsening ache after running. That picture points to Achilles tendinopathy rather than rupture. Rupture is sudden, focal, and dramatic; tendinopathy is gradual, achy, and worst in the morning. Distinguishing the two on the day of injury matters because the treatment paths are completely different.

The most reliable test is also the simplest — the Thompson test. You lie face-down on the exam table with your knee bent. Your provider squeezes your calf muscle. In a normal ankle, that squeeze tugs on an intact Achilles and the foot reflexively points downward. With a complete Achilles rupture, the link is broken: the foot doesn't move. Combined with the palpable gap above the heel and your inability to do a single-leg heel-rise, the Thompson test makes the diagnosis on the day you walk in. Ultrasound in clinic confirms the tear and — critically — measures the gap between the two torn ends, which influences whether you're a good candidate for non-operative treatment. MRI is reserved for complex or partial-tear pictures where the next step isn't obvious.

Surgical repair stitches the two torn ends of the tendon back together directly. Two approaches exist: an open repair through a small incision behind the ankle (with the surgeon visualizing both ends and tying them together with heavy suture), and a percutaneous repair that uses a much smaller incision with the suture passed through with specialized instruments. Both restore the tendon's length and tension precisely, which matters for athletes — even a few millimeters of lengthening at the repair site translates into measurable loss of push-off strength later. Surgery is the preferred path for younger, athletic patients who want the fastest reliable return to sport, and for ruptures with a wide gap that's unlikely to bridge non-operatively. Either way the boot-and-rehab protocol that follows looks broadly similar; the difference is mostly in re-rupture risk and peak push-off strength at one year, both of which favor surgery for the high-demand patient.

External patient-education references and related OSI pages for additional background:

• Britannica — Tendon
• Britannica — Ankle (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language