Achilles Tendon Injuries — The Spring That Snaps

As we move forward with our exploration of the lower leg, it's time to focus on the Achilles tendon itself — a structure that, much like its mythological namesake, has been the downfall of many.

While I don' claim to know a lot about basketball, even I couldn’t ignore the number of Achilles injuries cropping up in this year’s NBA playoffs. At least three notable players were sidelined or significantly impacted by Achilles tears. If you’re a fan whose team felt the sting, my condolences. But in the context of this article, I bring it up to emphasize a simple truth: even the best athletes in the world aren't immune to Achilles injuries.

Which makes it all the more important that we demystify what the Achilles tendon actually does, how it becomes injured, and how we can protect this essential link in the kinetic chain — maybe even bulletproof it.

Anatomy & Function

As we touched on in Part 1, the Achilles tendon is the tough, ropelike structure that connects your calf muscles (the gastrocnemius and soleus) to your heel bone (calcaneus).

Tendons, by design, are built to transmit force — taking the effort generated by muscle and applying it to bones to create movement or stability. Think of them as the ultimate force transmitters: thick, resilient, and spring-loaded for performance.

The Achilles tendon in particular is a masterclass in structural design. It’s made of densely woven collagen fibers — strong like a bridge cable, capable of handling and distributing stress efficiently. In fact, this tendon can withstand forces up to 10 times your body weight during high-level activity. Just like those suspension cables on a bridge, each microscopic “strand” of the tendon contributes to the strength and stability of the whole.

Achilles Cross Section

Bridge Cable Cross section

The Elastic Power of the Achilles

Whenever you push off during walking, running, or jumping, your Achilles tendon stores energy as your heel lowers — and then releases it like a spring to drive you forward. It’s one of the body’s most elegant force-management systems: absorbing, storing, and redirecting energy with each step.

But when the load exceeds what the tendon is ready to handle — whether suddenly or over time — problems can begin.

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Types of Achilles Injuries

For simplicity’s sake, we’ll break injuries into two broad categories:

Sudden-onset injuries

Overuse injuries

Sudden-Onset Injuries

These are often dramatic and unexpected. Most occur during explosive activities — sprinting, jumping, or forcefully pushing off the foot, especially when the tendon is under tension and the ankle is flexed upward.

Risk increases when:

• You’re deconditioned

• You’re fatigued

• You return to intense activity too quickly (after time off, illness, or injury)

These injuries can vary in severity:

• Grade I (Mild strain):

  • Microtears in tendon fibers. Usually managed with conservative care like rest, gradual loading, and PT.

• Grade II (Partial tear):

  • A more significant disruption of the tendon, often still managed non-surgically, but requiring structured rehab.

• Grade III (Full rupture):

  • A complete tear, often accompanied by a pop or the feeling of being kicked in the leg. These often require surgical repair, though certain non-surgical approaches can work in lower-demand individuals.

While we won’t dive into full rupture rehab in this article, it’s important to understand the full spectrum of injury — and what it might not be.

Overuse Injuries

These are the slow-burners. Most of the patients I see with Achilles pain describe a gradual increase in symptoms — no single “event,” just a growing discomfort.

Common causes:

• A sudden spike in training volume (like ramping up running mileage)

• Starting a new sport (hello, summer pickleball)

• Too little recovery between workouts

These injuries stem from repeated microloading on the tendon without enough rest or adaptation time. At first, the body responds with inflammation — a natural process that increases blood flow to help repair tissue. This phase is often called Achilles Tendonitis.

If the symptoms persist without proper loading and rest, the condition can progress to Achilles Tendinopathy, where the structure of the tendon begins to degrade. It becomes less effective at transmitting force, more painful, and more sensitive to load.

That said, having tendinopathy doesn’t mean you’re headed for a rupture. In fact, a 2017 study found that only 4% of Achilles tears had a known history of tendinopathy.

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Management Strategies

If you’re dealing with Achilles pain, the solution is almost never complete rest — and almost always smart loading.

Your goal should be to gradually expose the tendon to appropriate stress — enough to stimulate adaptation, but not so much that you flare symptoms.

In the clinic, we typically use:

• Manual therapy to restore mobility and calm irritated tissue

• Strength testing to determine where you're at — and what kind of load you can tolerate

• Progressive loading protocols to rebuild tendon strength and stiffness safely

Think of it as a training program for your tendon: not punishment, but practice.

Want to get started? Check out our Instagram account for some videos that demonstrate a simple, effective way to begin loading your Achilles safely and progressively.

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About the author: Dr. Alex Blank, PT, DPT, OCS, CFMT,

Alex is board certified as an orthopedic specialist and highly experienced in managing sports related injuries. He has extensive training in working with recreational and competitive athletes so that they can continue to participate in the activities they love!

Disclaimer: This blog post is for informational purposes only and does not substitute for professional medical advice. Please consult with a qualified healthcare professional for personalized guidance.