Overview
what it is and why it mattersYour Achilles is the rope-like tendon at the back of your ankle, formed where the two big calf muscles (the gastrocnemius and the soleus) merge and insert onto the back of your heel bone (the calcaneus). Achilles tendinopathy is what happens when that tendon wears down rather than tears outright — the classic running-injury picture, and the reason the older word "tendinitis" has been retired by people who treat it. There isn't much active inflammation; the problem is degenerative. Repeated overloading exceeds what the tendon can repair, the dense parallel collagen fibers that give the tendon its tensile strength get progressively disorganized, and the tendon itself thickens and aches under load.
Two locations dominate. Mid-portion tendinopathy sits 2 to 7 centimeters above the heel, in the same poorly-vascularized stretch surgeons call the watershed zone — the same spot where ruptures happen. On exam you can usually feel a discrete spindle-shaped nodule of thickened tendon there. Insertional tendinopathy sits right where the tendon meets the heel bone and often comes packaged with a small bony bump on the back of the calcaneus (a Haglund deformity) and a chronically irritated bursa wedged between the tendon and the bone. The two locations behave differently in rehab — eccentric loading works beautifully for mid-portion disease and only modestly for insertional — which is why pinpointing where it hurts matters.
Symptoms
how it usually shows upThe signature symptom is morning stiffness — the first few steps out of bed are stiff, painful, and tender, and the tendon "warms up" over the next ten or twenty minutes of walking until it feels almost normal. That warm-up pattern is so characteristic that it's nearly diagnostic on its own. Pain returns later in the day after a long run or a long shift on your feet, and it's worst the morning after a hard workout, not during it. Many runners describe being able to push through the workout itself only to be punished by the first steps out of bed the next day.
Squeezing the tendon between thumb and forefinger reproduces the pain in a small, focal spot. The tendon usually feels visibly thickened compared with the other side, and a small fusiform lump in the mid-portion variant is often visible to the naked eye. What's not typical: a sudden pop, a sharp stab of pain followed by inability to push off, or the feeling of being kicked in the back of the leg. Those point to Achilles rupture instead, which is the same tendon failing in a completely different way. Rupture is sudden and dramatic; tendinopathy is gradual and morning-loaded.
Diagnosis
exam first, imaging secondThe diagnosis is mostly clinical — the morning-stiffness story plus a thickened, tender tendon in a runner is enough most of the time. One useful exam trick is the Royal London Hospital test: tenderness over the mid-tendon that fades when your foot is pulled upward (because the painful nodule slides up under the surrounding tissue and is no longer directly squeezed). That maneuver helps separate true mid-portion tendinopathy from other causes of posterior heel pain. Ultrasound in clinic confirms the thickening and shows the disorganized, darker (hypoechoic) areas inside the tendon along with new abnormal blood vessels (neovascularization) — both hallmarks of chronic tendinopathy. MRI is reserved for cases where surgery is being planned or where the picture is unusual.
Treatment Path
how care progresses at OSIEccentric Loading Protocol (Alfredson)
Standing on a step with the front of your foot, you slowly lower the heel down past the level of the step, then use the other leg to come back up. The key is that slow, controlled lowering — the eccentric part of the contraction — which is the loading pattern that drives tendon remodeling. Performed twice a day, three sets of fifteen, for at least three months. It hurts during the workout in the early weeks; that's expected and not a sign you're doing damage. Modern evidence puts this at the top of the list for mid-portion tendinopathy and most patients see real change by week six to eight, with the full benefit landing closer to month three.
Load Management
The point isn't to stop running — it's to back the weekly load down to a level the tendon can tolerate while it's remodeling, then build it back up gradually. Cutting weekly mileage by 30 to 50 percent for several weeks while you do the eccentric program, then adding back ten percent at a time, is a typical approach.
Heel Lift
A small heel wedge inside your shoe shortens the tendon's working length, which reduces the tensile load on it during walking. Especially useful for insertional tendinopathy — taking pressure off the spot where the tendon meets the calcaneus often unlocks meaningful pain relief.
Physical Therapy
A formal heavy slow resistance (HSR) program with a physical therapist gives you a more structured, monitored version of the same eccentric-loading principle. Useful when home-based protocols stall or technique needs supervision.
PRP Injection
Important point: cortisone shots into the Achilles are avoided because they meaningfully raise the risk of rupture — this is one of the few orthopedic problems where a steroid injection is genuinely contraindicated. Platelet-rich plasma (PRP) draws on growth factors from your own blood to support tendon remodeling and can be combined with ultrasound-guided needling of the diseased portion of the tendon. Reserved for cases that haven't responded to a sustained eccentric program.
Surgical Options at OSI
if non-operative care isn't enoughSurgery is considered after a sustained trial of eccentric loading and adjunct therapies has failed to produce meaningful improvement.
Further Reading
authoritative sourcesExternal patient-education references and related OSI pages for additional background: