Achilles tendinopathy describes pain and stiffness in the thick band of tissue connecting the calf muscles to the heel bone (calcaneus). This condition is typically an overuse injury resulting from repeated stress that causes structural changes or tiny tears in the tendon fibers. While the term “tendonitis” suggests inflammation, chronic tendinopathy involves tendon degeneration rather than a primary inflammatory process. Pain in the posterior heel is common, but it is frequently misdiagnosed, as several other conditions mimic Achilles symptoms. Misdiagnosis can lead to prolonged, incorrect treatment, delaying recovery.
Conditions Involving Nearby Soft Tissue
The area surrounding the Achilles tendon contains soft tissue structures that can become irritated, causing pain nearly indistinguishable from true Achilles tendinopathy. The most common is retrocalcaneal bursitis, which involves the inflammation of a small, fluid-filled sac called the bursa. This bursa sits between the heel bone and the Achilles tendon, acting as a cushion to reduce friction.
When the bursa becomes inflamed due to excessive friction or compression, the resulting pain is felt deep inside the heel, just in front of the tendon. A key differentiator is that tenderness from bursitis is often felt on the sides of the lower Achilles tendon, whereas tendinopathy pain is usually felt directly on the tendon itself. Bursitis pain is also worse when the ankle is forcibly bent upward (dorsiflexion) because this movement compresses the inflamed bursa.
Paratendinitis, or inflammation of the paratenon, is another soft tissue issue that closely resembles Achilles tendinopathy. The paratenon is a thin layer of tissue that surrounds the main body of the Achilles tendon, helping it glide smoothly. Unlike true tendinopathy, which is a degenerative process, paratendinitis is a localized inflammatory reaction of this sheath.
Patients with paratendinitis often report a noticeable squeaking or creaking sensation, known as crepitus, when the ankle moves, resulting from the inflamed sheath rubbing against the tendon. This is a distinguishing factor, as crepitus is less common in isolated tendinopathy. Differentiating between insertional tendinopathy and retrocalcaneal bursitis is difficult, as the two conditions often occur together.
Skeletal and Structural Causes of Heel Pain
Pain that feels like a chronic Achilles problem can originate from the underlying bone structure, requiring a completely different treatment approach. A calcaneal stress fracture, a small crack in the heel bone, can be mistaken for severe tendinopathy, especially in runners or athletes. This injury results from repetitive mechanical stress that exceeds the bone’s ability to repair itself, usually following a sudden increase in activity level.
Unlike tendinopathy pain, which can sometimes lessen slightly with activity, the pain from a calcaneal stress fracture is often described as deep, aching, and constant, typically worsening with every weight-bearing step. Tenderness is often felt when the heel bone is squeezed from the sides, a test that is usually negative in isolated Achilles tendinopathy. Initial X-rays are often negative, contributing to misdiagnosis as a soft tissue injury, making advanced imaging like MRI necessary for confirmation.
Another structural issue is Haglund’s Deformity, an abnormal bony enlargement on the back of the heel bone. This prominence mechanically irritates the surrounding tissues, specifically the retrocalcaneal bursa and the Achilles tendon insertion. The constant rubbing caused by this bony bump leads to persistent inflammation that mirrors the symptoms of chronic insertional tendinopathy or bursitis.
The structural irritation is exacerbated by wearing rigid-backed shoes, which put direct pressure on the bony prominence, leading to a condition sometimes called “pump bump.” Posterior ankle impingement is where soft tissue or bone spurs are pinched in the back of the ankle joint, usually during forced plantarflexion. This condition produces pain at the back of the ankle that is easily confused with Achilles pain, but it is typically felt deeper within the joint itself.
Neurological Sources of Pain
Nerve-related pain can also be misinterpreted as chronic Achilles discomfort, requiring neurological interventions rather than physical therapy. The sural nerve runs close to the Achilles tendon and its insertion point on the heel. Irritation or entrapment of this nerve, known as sural nerve neuropathy, can cause a persistent ache often mistaken for tendinopathy.
A key difference is that nerve pain often presents with specific neurological symptoms such as burning, tingling, or numbness, especially along the outside (lateral) edge of the foot and ankle. This distinct pattern of sensation, called paresthesia, is rarely present in isolated tendon or bursal inflammation. The pain may also be reproduced by specific movements that stretch or compress the nerve, or by tapping directly over the nerve’s path (Tinel’s sign).
Pain in the posterior heel can also be referred from the lower spine, known as radiculopathy, such as with sciatica or lumbar disc issues. When a nerve root in the lower back is compressed, the pain can travel down the nerve pathway and be perceived in the ankle or heel. This referred pain often follows a predictable dermatomal pattern down the leg, a distribution that does not correlate with localized tendon pathology. Neurological symptoms such as muscle weakness or changes in reflexes provide strong evidence that the source of the pain is spinal rather than local.
Identifying Key Differences and Next Steps
Distinguishing between these various causes of posterior heel pain relies on a thorough physical examination. The exact location of tenderness is a primary differentiating factor: pain directly on the tendon suggests tendinopathy, pain deep between the tendon and the bone suggests retrocalcaneal bursitis, and pain on the sides of the heel bone suggests a calcaneal stress fracture. The quality of the pain also provides clues, with burning or tingling sensations pointing toward a neurological issue, while a deep, constant ache suggests a bone problem.
A healthcare professional will use specific physical tests, such as the calcaneal squeeze test for stress fractures or tests that put tension on the sural nerve, to narrow the diagnosis. Diagnostic imaging is often necessary, beginning with X-rays to assess for bony abnormalities like Haglund’s deformity or calcification within the tendon. If a stress fracture or soft tissue pathology is suspected but not confirmed by X-ray, an ultrasound or MRI scan can provide a clearer picture of the tendon, bursa, and bone marrow. Self-diagnosis is difficult and can delay correct treatment, making professional consultation the necessary next step.