Diagnosis of Achilles Tendinitis
The diagnosis of Achilles tendonitis is generally done clinically, meaning your doctor will ask you questions about your pain and perform a physical examination.

Physical Examination
A thorough physical exam of your foot and ankle is perhaps the key to diagnosing Achilles tendinitis. Some prime elements of the physical examination include inspecting and palpating (pressing on) the area around the Achilles tendon for swelling, warmth, crepitus (popping sensation) and tenderness.

Your doctor will also check the pulses in your feet and leg, access muscle strength and range of motion, and evaluate for foot misalignments and leg asymmetries.

Thompson Test
As part of the physical exam, in order to evaluate for an Achilles tendon rupture, your doctor will perform the Thompson test. With this test, a person lies flat on the exam table with his or her feet hanging over the edge of the table. The doctor will then squeeze on the calf muscle, which should flex the toes downward (called plantar flexion). If there is no plantar flexion, the test is positive for an Achilles tendon rupture.

Imaging
Imaging of the ankle is not generally needed to diagnose Achilles tendinitis, unless your doctor suspects a tendon rupture or that another condition is causing or contributing to your pain, such as a stress fracture. An ultrasound or an MRI may be used to diagnose an Achilles tendon rupture.