Achilles tendinitis is inflammation of the Achilles tendon, the thick band of tissue that connects your calf muscles to your heel bone. It causes pain at the back of your ankle or heel, typically coming on gradually rather than from a single injury. It’s one of the most common overuse injuries in runners and active adults, but it can affect anyone.
What the Achilles Tendon Does
The Achilles tendon is the largest and strongest tendon in your body. It acts as a lever: when your calf muscles contract, the tendon pulls on your heel bone and lifts your heel off the ground. This is the fundamental motion behind walking, running, jumping, and pushing off stairs. Every step you take loads this tendon with forces several times your body weight, which is why it’s so vulnerable to overuse.
Two Types Based on Pain Location
Achilles tendinitis shows up in two distinct patterns depending on where the damage occurs.
Non-insertional tendinitis affects the middle portion of the tendon, typically a few centimeters above the heel. This is the more common form in younger, active people. The tendon fibers in this zone have a relatively poor blood supply, which makes them slower to heal and more prone to breaking down with repetitive stress.
Insertional tendinitis involves the spot where the tendon attaches directly to the heel bone. Most people with this type report a gradual onset of pain and swelling at the back of the heel without any specific triggering injury. It’s commonly seen in runners, but contributing factors include older age, diabetes, being overweight, steroid use, changes in training habits, or poorly fitting shoes. Bone spurs can develop at the attachment site over time, making the condition harder to manage.
What Causes It
The core problem is repetitive stress that outpaces the tendon’s ability to repair itself. A sudden increase in running mileage, switching to hillier terrain, or jumping into a new sport without building up gradually are classic triggers. Tight calf muscles add extra load to the tendon with every step, and worn-out or unsupportive shoes remove the cushioning that helps absorb impact.
Several factors raise your risk beyond activity level. Obesity and physical exertion create high loads and sudden shifts in stress on the tendon. Aging causes deterioration in tendon cells, making the tissue less resilient. Autoimmune connective tissue disorders and kidney disease also increase vulnerability.
Certain medications are an underappreciated trigger. Fluoroquinolone antibiotics (a class that includes ciprofloxacin) are the most well-known pharmacological cause. They can damage the Achilles tendon in 90% of drug-related tendon cases, and 40% of those progress to a full rupture. The damage can appear as early as 48 hours into treatment or surface months after stopping the medication. In some cases, the tendon injury from these drugs is prolonged, disabling, and irreversible. Long-term use of corticosteroids and statins also carries tendon risk. Taking two or more of these medications together compounds the danger.
What It Feels Like
The hallmark symptom is pain and stiffness at the back of the ankle, especially first thing in the morning or after sitting for a long time. The tendon feels stiff and achy when you start moving, then loosens up somewhat with activity before worsening again later. You may notice swelling or a thickened, lumpy feeling along the tendon itself.
Pain typically increases with activities that load the tendon: running, climbing stairs, or pushing up onto your toes. In the early stages, you might only feel it during or after exercise. As the condition progresses, it can become constant enough to interfere with walking.
Tendinitis vs. Tendinosis
If your symptoms have lasted only a few weeks, you likely have true tendinitis, meaning the tendon cells are inflamed. This is an acute, short-term problem that responds well to rest and anti-inflammatory strategies. But when pain lingers for months, the condition often shifts into tendinosis, a chronic state where the inflammatory cells are replaced by degenerative ones. The tendon structure itself starts breaking down rather than just being irritated.
This distinction matters because treatments are different. Ice and anti-inflammatory medications help inflamed tissue but do little for a tendon that has entered the degenerative phase. Tendinosis requires strategies that stimulate the tendon to rebuild, like targeted loading exercises.
How It’s Diagnosed
A doctor can usually diagnose Achilles tendinitis through a physical exam. They’ll feel along the tendon for thickening, tenderness, or nodules, and ask you to move your ankle through its range of motion. If a rupture is suspected, they may perform a calf squeeze test: you lie face down while they squeeze your calf muscle. If the foot doesn’t move downward as expected, that suggests the tendon is torn rather than simply inflamed.
Imaging isn’t always necessary for a straightforward case, but an ultrasound or MRI can reveal the extent of damage, show whether the tendon has thickened or partially torn, and help distinguish tendinitis from tendinosis.
Treatment and Recovery
Most cases of Achilles tendinitis resolve without surgery, but recovery requires patience. The first step is reducing the load on the tendon. That doesn’t necessarily mean complete rest. It means backing off the activities that provoke pain, like running or jumping, while staying active in ways that don’t stress the tendon, such as swimming or cycling.
Ice, compression, and over-the-counter pain relievers can help manage symptoms in the acute phase. Heel lifts placed inside your shoes reduce the stretch on the tendon and can provide quick relief. Physical therapy is the cornerstone of treatment for anything beyond a mild case.
Eccentric Loading Exercises
The most well-studied rehabilitation exercise for Achilles tendinitis is the eccentric heel drop. You stand on the edge of a step, rise up on your toes, then slowly lower your heel below the level of the step. The lowering phase is the key part. It forces the tendon to absorb load while lengthening, which stimulates repair and remodeling of damaged tissue. The standard protocol calls for 3 sets of 15 repetitions, performed twice daily, seven days a week, for 12 weeks. It’s normal for the exercise to cause mild discomfort, but sharp or worsening pain is a signal to back off.
This program works, but 12 weeks is a real commitment, and progress often feels slow in the first month. Many people notice meaningful improvement between weeks four and eight.
Shockwave Therapy
For chronic cases that don’t respond to exercise alone, extracorporeal shockwave therapy is an option. The treatment delivers pressure waves into the tendon to stimulate the body’s own healing response. Most patients notice some improvement within the first three months. It’s typically used as an intermediate step before considering surgery.
When Surgery Becomes an Option
If symptoms persist after several months of consistent conservative treatment, surgery may be recommended. The specific procedure depends on the type and extent of damage. For insertional tendinitis, this might involve removing bone spurs and repairing the damaged portion of the tendon. For non-insertional cases, the surgeon may remove degenerated tissue from the middle of the tendon. Recovery after surgical repair involves a walking boot and crutches for the first few weeks, followed by a structured physical therapy program lasting 12 to 16 weeks.
Preventing Recurrence
Achilles tendinitis has a high recurrence rate, especially if you return to full activity too quickly. The single most effective prevention strategy is consistent calf strengthening. Continuing eccentric heel drops two to three times per week even after symptoms resolve helps keep the tendon resilient. Increasing training volume by no more than 10% per week is a widely used guideline for runners. Replacing worn shoes regularly, warming up before intense activity, and addressing tight calves through stretching or foam rolling all reduce your risk of a flare-up.
If you take fluoroquinolone antibiotics or long-term corticosteroids, be aware of tendon symptoms and report any new heel or ankle pain to your prescriber promptly. Early intervention, before the tendon progresses from inflammation to degeneration, makes a significant difference in recovery time.