Achilles Tendinopathy: Symptoms, Causes & Treatment

Achilles tendinopathy encompasses a spectrum of painful degenerative conditions affecting the Achilles tendon — the largest and strongest tendon in the body, formed by the confluence of the gastrocnemius and soleus muscle tendons and inserting into the posterior calcaneus. Two anatomical subtypes are recognized: (1) Midportion Achilles tendinopathy (MAT): located 2–6 cm proximal to the calcaneal insertion — the most common form (accounting for 55–65% of cases); (2) Insertional Achilles tendinopathy (IAT): at the calcaneal insertion — associated with Haglund's deformity and retrocalcaneal bursitis.

Contemporary understanding of pathophysiology has shifted away from the 'tendinitis' (inflammatory) model. Tendinopathy is fundamentally a degenerative process ('failed healing') — characterized by disorganized collagen fibrils, increased non-sulfated proteoglycans (aggrecan, versican), and neovascularization accompanied by aberrant neural ingrowth. This neurovascular ingrowth is the source of pain. The condition is better described as 'tendinopathy' rather than 'tendinitis' because inflammatory cells are largely absent in chronic disease.

Achilles tendinopathy has a point prevalence of 2.35% in general population and is the most common overuse injury in long-distance runners (annual incidence ~9–11%). Risk factors include training errors (sudden volume/intensity increase), poor footwear, hard surfaces, limited ankle dorsiflexion, overweight, and fluoroquinolone antibiotic use (direct tenocyte toxicity). Evidence-based rehabilitation — particularly heavy slow resistance (HSR) tendon loading — achieves good to excellent outcomes in 60–80% of patients over 12 weeks.

• Localized Achilles tendon pain: characteristically worst with initial steps in the morning or after rest (stiffness/pain), improving briefly with activity (warm-up phenomenon), then worsening again with prolonged or high-load activity
• Morning stiffness lasting 15–30 minutes in the Achilles region
• Fusiform mid-tendon thickening (midportion) or bony prominences at insertion (insertional)
• Tenderness on palpation — the arc sign: tender area moves with tendon (= tendon itself); if tender area stays fixed while tendon moves = peritendinous pathology
• Reduced calf strength on single-leg calf raise testing

• Training errors: sudden increase in running volume, intensity, or surface hardness
• Calf muscle weakness and inflexibility: reduced eccentric strength and limited ankle dorsiflexion
• Biomechanical factors: overpronation, cavus foot, increased forefoot strike
• Overweight and sedentary lifestyle with sudden increase in physical activity
• Fluoroquinolone antibiotics (ciprofloxacin, levofloxacin): direct tenocyte toxicity — most significant drug cause; caution with co-prescription of corticosteroids
• Systemic conditions: diabetes, hyperlipidemia (xanthomatous tendinopathy in FH), gout
• Intrinsic factors: aging-related collagen degeneration; tendon vascularity naturally decreases after age 30

Primarily clinical diagnosis: characteristic symptom pattern (morning stiffness, activity-related pain with warm-up phenomenon) + palpation findings (focal tenderness, thickening, arc sign). VISA-A (Victorian Institute of Sport Assessment — Achilles) questionnaire: validated outcome measure for monitoring tendinopathy severity (0–100 scale). Musculoskeletal ultrasound: confirms tendon thickening, hypoechoic areas (collagen disorganization), neovascularization on Doppler; detects partial or complete rupture. MRI: superior for complex presentations, surgical planning, and excluding insertional pathology (Haglund's deformity, retrocalcaneal bursitis). Plain X-ray: detects calcific insertional tendinopathy and Haglund's deformity.

Exercise therapy is the cornerstone with the strongest evidence: Heavy Slow Resistance (HSR) tendon loading — slow concentric + eccentric loading using leg press or calf raises with added weight (3 sets × 6–8 reps, 3-second concentric + 3-second eccentric, 3 days/week for 12 weeks) — reorganizes collagen, reduces pain, and achieves good outcomes in 60–80%. Eccentric-only training (Alfredson protocol): 3×15 reps on a step, twice daily for 12 weeks — well-evidenced for midportion but less effective for insertional. Heel lifts: reduces Achilles load acutely — helpful for insertional. NSAIDs: for acute pain relief; limited long-term role. Ultrasound-guided injections: PRP (platelet-rich plasma), high-volume image-guided injection, or sclerotherapy for neovascularization — second-line for non-responders. Shockwave therapy (ESWT): evidence supports use for chronic tendinopathy. Surgery: reserved for refractory cases after ≥6 months of proper conservative treatment; tendon debridement and neovascular ablation.

• Achilles tendon rupture: degenerated tendons are at higher risk; risk substantially increased by intratendinous corticosteroid injection and fluoroquinolone antibiotics
• Chronic pain and functional limitation from untreated or mismanaged tendinopathy
• Inability to return to sport in severe or surgically treated cases

• Progressive training load increases (<10% weekly volume increase — the 10% rule)
• Calf strengthening (gastrocnemius + soleus isolation) incorporated into regular training
• Appropriate footwear with adequate heel cushioning and control
• Avoid intratendinous corticosteroid injections — increase rupture risk without long-term benefit for tendinopathy
• Caution with fluoroquinolone antibiotics in athletes and physically active patients — switch to alternatives when possible