Achilles Pain — Tendinopathy or Rupture?
Achilles pain can be unsettling. One day it may feel like a tight, niggling ache at the back of the heel; another day it may become sharp, swollen, or suddenly disabling. Many people worry about the same question: is this Achilles tendinopathy, a partial tear, or a rupture?
The Achilles tendon is the strongest tendon in the body, connecting the calf muscles to the heel bone. It is essential for walking, climbing stairs, running, jumping, and pushing off the foot. Because it carries high loads, it is also vulnerable to irritation, degeneration, tearing, and acute injury.
This article explains the main causes of Achilles pain, how symptoms differ, when to seek urgent help, and how musculoskeletal ultrasound can help distinguish Achilles tendinopathy, partial tear, and rupture.
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⚠ Red Flags: When Achilles Pain Needs Urgent Medical Attention
Most Achilles pain is not an emergency, but certain symptoms should be assessed urgently.
Please seek same-day urgent care or A&E if you have:
- A sudden “pop” or “snap” in the back of the ankle or calf
- Immediate difficulty walking or pushing off the foot
- A feeling that you were “kicked” or struck in the back of the leg
- A visible gap or dent in the Achilles tendon
- Sudden weakness when trying to stand on tiptoe
- Rapid swelling or bruising after an injury
- Severe pain after a fall or sporting injury
- Fever, spreading redness, warmth, or discharge around the heel or ankle
- Calf swelling, tightness, redness, or shortness of breath — possible signs of deep vein thrombosis, which requires urgent assessment
A suspected Achilles rupture is time-sensitive. Early diagnosis helps guide immobilisation, specialist referral, and the decision between conservative and surgical management.
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At a Glance
| Symptom pattern | Possible cause | Typical urgency |
|---|---|---|
| Gradual stiffness and pain during or after activity | Achilles tendinopathy | Routine MSK assessment |
| Pain 2–6 cm above the heel, worse with running or hills | Mid-portion tendinopathy | Routine MSK assessment |
| Pain where the tendon inserts into the heel bone | Insertional tendinopathy | Routine MSK assessment |
| Focal sharp pain after overload, but still able to walk | Partial tear | Prompt assessment |
| Sudden snap, pop, weakness, difficulty walking | Achilles rupture | Urgent assessment |
| Red, hot, swollen skin or fever | Infection or inflammatory condition | Urgent medical review |
| Calf swelling, tenderness, breathlessness | Possible DVT | Urgent medical review |
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Understanding the Achilles Tendon
The Achilles tendon is formed by the gastrocnemius and soleus muscles of the calf. It attaches to the back of the heel bone, known as the calcaneus.
Clinically, Achilles problems are often described by location:
Mid-portion Achilles pain
This is usually felt 2–6 cm above the heel bone. It is the classic site for mid-portion Achilles tendinopathy. The tendon may feel thickened, tender, or stiff, especially first thing in the morning.
Insertional Achilles pain
This is felt where the tendon attaches to the heel. It may be associated with bony prominence, irritation from footwear, retrocalcaneal bursitis, or calcification within the tendon. Management can differ from mid-portion tendinopathy, so identifying the location matters.
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Achilles Tendinopathy: The Common Gradual Cause
Achilles tendinopathy is one of the most common causes of Achilles pain. It is often described as “tendonitis”, but modern research shows that persistent tendon pain is usually not simple inflammation. Instead, it involves changes in tendon structure, load tolerance, collagen organisation, and tendon healing response.
Typical symptoms include:
- Gradual onset pain at the back of the ankle or heel
- Morning stiffness that improves after moving around
- Pain at the start of exercise, sometimes easing during activity
- Symptoms that worsen after running, jumping, hills, or sudden training increases
- Localised tenderness or thickening of the tendon
- Reduced confidence pushing off the foot
Tendinopathy often develops when the tendon is asked to tolerate more load than it is ready for. This may happen after:
- Increasing running distance or speed too quickly
- Adding hill training or interval training
- Returning to sport after a break
- Changing footwear
- Taking up tennis, padel, football, or gym-based jumping exercises
- Calf weakness or reduced ankle mobility
- Metabolic factors, including diabetes or high cholesterol
- Certain medications, including fluoroquinolone antibiotics or corticosteroids
Achilles tendinopathy can be painful, but it does not automatically mean the tendon is about to rupture. However, persistent pain should be assessed if it is worsening, limiting activity, or not improving with sensible load modification.
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Mid-portion vs Insertional Achilles Tendinopathy
The distinction between mid-portion and insertional tendinopathy is clinically important.
Mid-portion Achilles tendinopathy
Mid-portion tendinopathy usually affects the tendon above the heel bone. The tendon may appear thickened and tender. Pain is often linked to running, jumping, or repeated push-off activity.
On ultrasound, findings may include:
- Tendon thickening
- Altered fibre pattern
- Hypoechoic regions within the tendon
- Increased Doppler signal in some cases
- Paratenon irritation or fluid around the tendon
Insertional Achilles tendinopathy
Insertional tendinopathy affects the attachment to the heel bone. Pain is often very focal at the back of the heel. Shoes may aggravate symptoms. Some people also have a prominent heel contour or irritation of the retrocalcaneal bursa.
On ultrasound, findings may include:
- Thickening near the tendon insertion
- Calcification or enthesophyte formation
- Retrocalcaneal bursitis
- Fluid or irritation around the insertion
- Partial insertional tearing in more advanced cases
Some rehabilitation exercises used for mid-portion tendinopathy may need modification in insertional tendinopathy, particularly exercises that place the ankle into deep dorsiflexion over a step.
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Partial Achilles Tear: The Grey Zone
A partial tear sits between tendinopathy and complete rupture. It means some tendon fibres are disrupted, but the tendon remains partly intact.
Partial tears can be difficult to recognise from symptoms alone because they may resemble a flare of tendinopathy. Some patients can still walk, although with pain.
Symptoms may include:
- A sharper, more localised pain than usual
- Pain after a sudden increase in load or awkward movement
- Swelling or bruising around the tendon
- A tender focal defect or soft area
- Pain when rising onto the toes
- A feeling that the tendon is unreliable
Partial tears are important because management may differ from routine tendinopathy. Continuing high-load activity on a partially torn tendon can risk worsening the injury.
Ultrasound can be very useful because it allows direct assessment of tendon fibres and can identify focal defects, haematoma, fluid, or preserved continuity.
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Achilles Rupture: The Sudden “Snap”
An Achilles rupture is a complete or near-complete tear of the tendon. It often occurs during sport, sudden acceleration, jumping, or pushing off, but it can also happen during everyday movement.
Classically, patients describe:
- A sudden snap, pop, or tearing sensation
- Feeling as if someone kicked them in the calf
- Immediate weakness
- Difficulty walking normally
- Difficulty standing on tiptoe
- Swelling and bruising
- Sometimes surprisingly little pain after the initial event
A rupture can be missed, especially if the patient can still limp or move the ankle using other muscles. That is why sudden weakness after a snap should always be taken seriously.
Clinical tests, such as the calf squeeze test, can raise suspicion, but imaging may be needed to confirm the diagnosis, assess the extent of injury, and guide referral.
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Achilles Tendinopathy vs Partial Tear vs Rupture
| Feature | Achilles tendinopathy | Partial Achilles tear | Achilles rupture |
|---|---|---|---|
| Onset | Usually gradual | Often sudden or after overload | Sudden |
| Sensation | Ache, stiffness, soreness | Sharp focal pain | Pop, snap, or “kicked” feeling |
| Walking ability | Usually possible | Often possible but painful | Often difficult; may limp |
| Tiptoe strength | Painful but possible | Painful or weak | Often markedly weak or impossible |
| Swelling | Mild to moderate | Local swelling possible | Swelling and bruising common |
| Tendon feel | Thickened or tender | Focal tenderness or defect | Possible palpable gap |
| Urgency | Routine assessment unless severe | Prompt assessment | Urgent assessment |
| Ultrasound role | Tendon structure and Doppler | Fibre disruption and tear size | Continuity and dynamic gap assessment |
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How Ultrasound Helps Diagnose Achilles Pain
Musculoskeletal ultrasound is well suited to the Achilles tendon because the tendon lies close to the skin and can be examined dynamically.
At IUS London, Achilles ultrasound may assess:
- Tendon thickness
- Fibre structure
- Tendon continuity
- Mid-portion vs insertional involvement
- Partial tears
- Complete rupture
- Fluid around the tendon
- Paratenon irritation
- Retrocalcaneal bursitis
- Calcification or enthesophytes
- Doppler signal suggesting increased vascularity
- Dynamic movement during gentle ankle motion
Dynamic gap assessment in suspected rupture
One of the advantages of ultrasound is the ability to assess the tendon dynamically. In suspected rupture, the sonographer can evaluate whether tendon ends remain opposed or whether a gap opens during movement.
This dynamic gap assessment may help clinicians understand the extent of rupture and can support appropriate referral pathways. It does not replace orthopaedic decision-making, but it provides valuable anatomical information.
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Ultrasound vs MRI for Achilles Pain
Both ultrasound and MRI can assess Achilles tendon pathology. The most appropriate test depends on the clinical question.
| Feature | MSK ultrasound | MRI |
|---|---|---|
| Tendon fibre assessment | Excellent for superficial tendon fibres | Excellent for full regional anatomy |
| Dynamic assessment | Yes — real-time movement and gap assessment | No — static imaging |
| Partial tears | Often well demonstrated | Well demonstrated |
| Complete rupture | Often clearly identified | Clearly identified |
| Bursitis and fluid | Well demonstrated | Well demonstrated |
| Bone marrow changes | Limited | Excellent |
| Speed and access | Usually faster | Often longer wait |
| Patient position | Comfortable, targeted | Requires scanner time and stillness |
| Best use | Focused Achilles assessment, dynamic evaluation, guided triage | Complex cases, surgical planning, unclear wider pathology |
For many patients with focal Achilles pain, ultrasound is an efficient first-line imaging test. MRI may be recommended when symptoms are complex, when deeper structures need assessment, or when a specialist requires further mapping.
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Other Causes of Pain Around the Achilles
Not all pain at the back of the heel is caused by the tendon itself. Possible alternatives include:
Retrocalcaneal bursitis
The retrocalcaneal bursa sits between the Achilles tendon and heel bone. It can become inflamed, causing pain just in front of the tendon insertion. This is often associated with insertional Achilles tendinopathy.
Paratenonitis
The Achilles tendon does not have a typical tendon sheath, but it is surrounded by a paratenon. Irritation here can cause pain, creaking, and swelling around the tendon.
Plantaris tendon involvement
The plantaris tendon is a small tendon running near the Achilles in some people. It may contribute to medial Achilles pain in selected cases.
Haglund’s deformity
A bony prominence at the back of the heel can irritate surrounding soft tissues, especially in stiff footwear.
Calf muscle injury
A calf strain can mimic Achilles pain, especially if the pain is higher in the lower leg.
Referred or nerve-related pain
Lumbar spine or nerve irritation can occasionally contribute to symptoms around the heel or calf, although this is less typical.
A focused clinical history and ultrasound examination can help narrow the likely cause.
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What to Do While Waiting for Assessment
If your pain is mild and developed gradually, it is usually sensible to reduce aggravating load rather than stop all movement.
You may consider:
- Avoiding running, jumping, sprinting, and hills temporarily
- Switching to lower-impact activity, such as cycling if comfortable
- Wearing supportive footwear
- Avoiding barefoot walking if it worsens pain
- Using a small heel raise temporarily if advised
- Avoiding aggressive calf stretching if insertional pain is present
- Seeking physiotherapy guidance for progressive loading
If you suspect a partial tear or rupture, do not “test it” repeatedly by hopping or trying to stand on tiptoe. Seek prompt medical assessment.
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From Our Practice
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At IUS London, a common presentation pattern in MSK ultrasound is the patient who books because of “Achilles tendonitis” after several weeks of heel pain, often following a return to running, tennis, or gym classes.
In many of these cases, ultrasound shows mid-portion Achilles tendinopathy with tendon thickening rather than a rupture. However, we also see patients who describe a sudden change — a sharp pain or small “pop” during activity — where ultrasound identifies a focal partial tear within a background of tendinopathy.
Operationally, when a patient reports a sudden snap, marked weakness, or difficulty walking, the case is treated differently from routine tendon pain. The priority is to identify or exclude rupture and support appropriate urgent referral if needed.
This distinction matters: gradual tendon pain and sudden tendon failure can feel similar in the first few days, but they often need different next steps.
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What Happens During an Achilles Ultrasound?
An Achilles ultrasound is usually straightforward and well tolerated.
You may be asked to lie face down or kneel with the feet positioned so the tendon can be examined from the calf to the heel. Gel is applied to the skin, and a high-frequency ultrasound probe is moved along the tendon.
The examination may include:
- Comparing the painful side with the other side
- Assessing the tendon lengthways and crossways
- Checking the tendon insertion
- Evaluating the surrounding bursa and soft tissues
- Looking for tears, fluid, thickening, or calcification
- Using Doppler to assess vascularity
- Gentle dynamic manoeuvres, where appropriate
If a rupture is suspected, the scan is performed carefully and gently.
The aim is not simply to “find something”, but to answer the clinical question.
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How Imaging Fits Into Treatment
Ultrasound findings should be interpreted alongside symptoms and clinical examination. Tendon changes on imaging do not always perfectly match pain levels. Some people have structural tendon changes with little pain, while others have significant symptoms with more subtle imaging findings.
For tendinopathy, treatment commonly involves:
- Load management
- Progressive calf strengthening
- Sport-specific rehabilitation
- Addressing biomechanics and training errors
- Footwear review
- Time and consistency
For partial tears, management may involve:
- More careful protection from load
- Physiotherapy or sports medicine input
- Temporary immobilisation in selected cases
- Follow-up imaging if clinically indicated
For rupture, management may involve:
- Immobilisation
- Urgent orthopaedic or fracture clinic referral
- Discussion of functional bracing vs surgery
- Rehabilitation under specialist guidance
The best next step depends on the diagnosis, the tendon gap, the patient’s activity level, medical background, and specialist assessment.
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Frequently Asked Questions
Can I walk on an Achilles rupture?
Some people can still limp after an Achilles rupture, which is one reason ruptures can be missed. If you felt a sudden snap or have marked weakness, do not rely on walking ability alone. Seek urgent assessment.
Is Achilles tendinopathy the same as tendonitis?
The term “tendonitis” suggests inflammation, but persistent Achilles pain is usually better described as tendinopathy. It involves changes in tendon structure and load capacity, not just inflammation.
Does a thickened Achilles tendon mean it is torn?
Not necessarily. Tendon thickening is common in tendinopathy. Ultrasound can help distinguish thickening from a partial tear or complete rupture.
Can ultrasound show a partial Achilles tear?
Yes. Ultrasound can identify focal fibre disruption, tendon defects, fluid, and associated tendinopathy. It is particularly useful because the Achilles tendon is superficial and can be assessed dynamically.
Is MRI better than ultrasound?
MRI is excellent for complex anatomy and surgical planning, but ultrasound is often highly effective for focused Achilles assessment. It also allows real-time dynamic evaluation, including assessment of tendon movement and gap behaviour.
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When to Book an MSK Ultrasound
Consider booking an Achilles ultrasound if you have:
- Achilles pain lasting more than 1–2 weeks despite reducing activity
- Recurrent pain during running or sport
- Localised tendon thickening or swelling
- Insertional heel pain
- Concern about a partial tear
- A sudden change in symptoms after a sharp pain or pop
- Uncertainty about whether the pain is tendon, bursa, or calf-related
If you suspect a complete rupture, especially after a sudden snap with weakness, seek urgent medical care rather than waiting for a routine appointment.
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Book a Private MSK Ultrasound Scan in London
If you are experiencing Achilles pain and want clarity on whether it may be tendinopathy, a partial tear, rupture, or another soft-tissue cause, IUS London provides focused private musculoskeletal ultrasound assessment.
Book your scan here: Private MSK Ultrasound Scan
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References
1. Khan KM, Cook JL, Kannus P, Maffulli N, Bonar SF. Time to abandon the “tendinitis” myth. BMJ. 2002;324(7338):626-627. doi: 10.1136/bmj.324.7338.626
2. Silbernagel KG, Hanlon S, Sprague A. Current clinical concepts: conservative management of Achilles tendinopathy. Journal of Orthopaedic & Sports Physical Therapy. 2020;50(12):680-692. doi: 10.2519/jospt.2020.9529
3. Soroceanu A, Sidhwa F, Aarabi S, Kaufman A, Glazebrook M. Surgical versus nonsurgical treatment of acute Achilles tendon rupture: a meta-analysis of randomized trials. Journal of Bone and Joint Surgery American Volume. 2012;94(23):2136-2143. doi: 10.2106/JBJS.K.00917
4. Gulati V, Jaggard M, Al-Nammari SS, et al. Management of Achilles tendon injury: a current concepts systematic review. World Journal of Orthopedics. 2015;6(4):380-386. doi: 10.5312/wjo.v6.i4.380
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