Achilles Tendonitis

The Achilles tendon is the largest and strongest tendon in the body, a thick, rope-like structure connecting the calf muscles to the heel bone. It is the tendon you use every time you walk, run, climb stairs, or push off the ground. Achilles tendonitis is inflammation or degeneration of this tendon, causing pain and stiffness at the back of the lower leg, typically just above the heel.

It is one of the most common overuse injuries in runners and active adults, but it also affects those who are less active — particularly when activity level suddenly increases or footwear provides inadequate support. The condition ranges from a mild ache that settles with rest to a chronic, debilitating pain that limits daily function and requires structured treatment to resolve.

Understanding the Achilles Tendonitis?

The Achilles tendon runs from the gastrocnemius and soleus muscles in the calf to the posterior aspect of the calcaneus (heel bone). It is the thickest and strongest tendon in the human body, capable of withstanding forces of up to eight times body weight during running.

Despite its strength, the Achilles tendon has a relatively poor blood supply — particularly in the mid-portion, approximately 2–6 cm above the heel bone. This vascular watershed zone is where most non-insertional Achilles tendonitis and ruptures occur. The poor blood supply means the tendon heals more slowly than muscle tissue and is more susceptible to cumulative overload.

The term tendonitis (or tendinitis) implies active inflammation. The more accurate term for most chronic cases is tendinopathy — a degenerative process in which the normal, well-organised collagen fibres of the tendon become disorganised, with microscopic damage accumulating faster than the tendon can repair itself. This distinction matters for treatment: truly inflammatory tendonitis responds to anti-inflammatory measures; degenerative tendinopathy requires load-based rehabilitation to stimulate tissue remodelling.

Symptoms of Achilles Tendonitis

Symptoms typically develop gradually over days to weeks, though a sudden worsening of pre-existing tendon discomfort can occur after a single intense session. The classic presentation includes:

Early symptoms

• A mild ache or stiffness at the back of the lower leg or just above the heel, typically after exercise
• Stiffness that is worst in the morning or after a period of rest, improving with gentle movement
• Tenderness when you press along the tendon or at the heel attachment
• Mild swelling or localised thickening of the tendon

Symptoms as the condition progresses

• Pain that persists during exercise rather than just afterwards
• A visible or palpable nodular thickening along the tendon (particularly in non-insertional cases)
• Pain that limits the duration or intensity of activity
• Significant morning stiffness — difficulty taking the first steps after getting out of bed
• Weakness in the lower leg — difficulty rising onto tiptoe or pushing off during walking

Symptoms requiring urgent assessment

• A sudden snap, crack, or pop in the back of the lower leg — particularly during a sprint or jump
• Immediate inability to bear weight or push off with the foot
• A palpable gap or depression in the tendon above the heel

Who is at Risk of Achilles Tendonitis?

There are a number of factors that may increase your risk of Achilles Tendonitis:

• Age: Tendon tissue loses elasticity and vascularity with age. Achilles tendinopathy becomes more common over 30, with peak incidence in the 40–60 age range.
• Gender: Men are approximately two to three times more likely to develop Achilles tendonitis than women, for reasons that include differences in tendon loading patterns and body mechanics.
• Intensity of Activity: Adding distance, intensity, or frequency to running or sport too quickly is the most common trigger. The 10% rule — increasing load by no more than 10% per week — exists to prevent this.
• Medical Condition: Psoriasis, hypertension, gout, and rheumatoid arthritis increase the risk of Achilles tendon pathology. Systemic inflammation affects tendon tissue quality and healing capacity.
• Physical Condition: Flat arches on the foot may put more strain on the Achilles Tendon. Obesity can also apply extra weight to your tendon, increasing your risk of straining it.
• Tight calf muscles: Inadequate flexibility in the gastrocnemius or soleus increases the load transmitted to the Achilles tendon during activity. Poor warm-up exacerbates this.

How do you prevent Achilles Tendonitis?

Although it may not be possible to completely prevent Achilles Tendonitis, there are still steps you can take to lower your risk of developing the condition:

• Alternate activity: Alternate between high-impact sports such as running and jumping with low impact sports like swimming and cycling to reduce the strain on your tendons.
• Gradual changes to your workout: If you are staring a new exercise regime, start slowly before gradually increasing the duration and intensity of the training. If you notice pain during a particular exercise, stop and rest.
• Frequent streches: Taking the time to stretch your calf muscles and Achilles tendon daily, not just before and after exercising, will help increase their flexibility.
• Proper warm-ups: Warm up your muscles sufficiently, especially before strenuous exercise.
• Wearing the right shoes: Having firm arch support will help to reduce strain and tension in the Achilles tendon. If your shoes are in good condition but don't support your feet, try arch supports in both shoes.

How is Achilles Tendonitis Diagnosed?

Diagnosis is primarily clinical — your orthopaedic specialist will examine the tendon, assess its tenderness, identify whether the pathology is insertional or non-insertional, and test lower limb strength and function. Imaging is used to confirm the extent of tendon involvement and to exclude rupture or other pathology.

Clinical Assessment

• Palpation of the tendon to locate the point of maximum tenderness and assess for thickening or nodularity
• Squeezing the tendon at its thickest point — in non-insertional tendinopathy, this may reduce pain on dorsiflexion, distinguishing tendon pathology from paratendinitis
• Single-leg calf raise test: assessing the ability to perform 25 repetitions of single-leg heel rises, which is reduced in tendinopathy
• Calf squeeze test: Squeezing the calf with the patient prone — absence of plantar flexion indicates complete Achilles tendon rupture
• Assessment of foot biomechanics, ankle range of motion, and calf flexibility

Imaging

• Ultrasound: First-line imaging for Achilles tendon assessment. Shows tendon thickness, internal architecture, neovascularisation (new blood vessel ingrowth associated with tendinopathy), and partial tears. Dynamic assessment allows evaluation of tendon movement. Available in the Diagnostic Imaging Suite at Farrer Park Hospital.
• MRI: Most detailed assessment of tendon structure, identifying the extent of degeneration, partial tears, paratenon involvement, and insertional pathology including bone marrow oedema in the calcaneum. Preferred when surgical planning or tendon rupture assessment is needed.
• X-ray: Limited value for soft tissue tendon assessment, but useful to identify bony prominence or calcification within the tendon at the insertion.

Recovery and Return to Activity

Recovery from Achilles tendonitis is measured not just in pain reduction but in return to full, unrestricted activity. The timeline varies significantly by severity, how long the condition has been present before treatment began, and how consistently rehabilitation is followed.

Acute Phase (Weeks 1-4)

Load management and relative rest. Begin gentle range of motion and non-painful eccentric exercises. Ice after activity. Goal: reduce pain to a manageable level and begin tendon loading programme.

Rehabilitation Phase (Weeks 4-12)

Progressive eccentric loading under physiotherapy guidance. Gradual reintroduction of sport-specific movement patterns. Footwear optimisation. Goal: restore tendon capacity and address biomechanical factors.

Return to Running (Weeks 8-16)

Structured return-to-running programme, typically starting with walk-run intervals. Volume and intensity increase based on symptom response (pain should remain ≤3/10 during and after sessions). Goal: return to pre-injury running distance.

Return to Sports (3-6 months)

Return to unrestricted sport including speed work, hill running, and jumping. A strength and conditioning programme continues to protect the tendon and prevent recurrence. Goal: full return with reduced risk of reinjury.

Chronic Achilles tendinopathy — where symptoms have been present for many months before treatment begins — requires a longer rehabilitation timeline. Patients should be counselled that improvement is gradual and that the tendon may not be completely pain-free for 6–12 months.

The goal of treatment is progressive functional improvement and return to meaningful activity, not necessarily complete elimination of all discomfort before resuming sport.