How can I differentiate between plantar fasciitis and Achilles tendinopathy in a patient presenting with heel pain?

To differentiate plantar fasciitis from Achilles tendinopathy in a patient presenting with heel pain, focus on the location and characteristics of the pain, as well as clinical examination findings.

• Location of pain: Plantar fasciitis typically causes pain at the medial calcaneal tubercle on the plantar aspect of the heel, whereas Achilles tendinopathy presents with pain at the posterior heel, specifically along the Achilles tendon above its insertion on the calcaneus NICE NG19 Alvarez-Nemegyei 2006.
• Onset and pain pattern: Plantar fasciitis pain is often worst with the first steps in the morning or after periods of rest, improving with activity but potentially worsening later in the day. Achilles tendinopathy pain usually worsens with activity, especially during or after exercise involving ankle dorsiflexion and plantarflexion Alvarez-Nemegyei 2006 NICE NG19.
• Palpation findings: Tenderness in plantar fasciitis is localized to the plantar fascia origin at the medial calcaneal tubercle, while Achilles tendinopathy shows tenderness and sometimes thickening along the Achilles tendon, typically 2–6 cm proximal to its insertion McNally & Shetty 2010 NICE NG19.
• Functional tests: Dorsiflexion of the toes and ankle may exacerbate plantar fasciitis pain due to tension on the plantar fascia, whereas resisted plantarflexion or stretching of the Achilles tendon reproduces pain in Achilles tendinopathy McNally & Shetty 2010 NICE NG19.
• Imaging: Ultrasound or MRI can help confirm diagnosis if clinical uncertainty remains. Plantar fasciitis shows thickening and hypoechoic changes at the plantar fascia origin, while Achilles tendinopathy demonstrates tendon thickening, hypoechoic areas, and neovascularization within the tendon substance McNally & Shetty 2010 NICE NG19.

In summary, the key differentiators are the anatomical site of pain and tenderness, pain behavior with activity and rest, and specific clinical tests targeting the plantar fascia versus the Achilles tendon.