Heel or Elbow Pain That Won’t Quit: How to Tell Enthesitis From Tendonitis and Plantar Fasciitis

If you search “heel pain” or “elbow pain,” you will quickly run into three common labels—enthesitis, tendonitis (often more accurately called tendinopathy), and plantar fasciitis. They get confused because they all involve pain near where soft tissue meets bone, and they often flare with walking, running, lifting, or long hours on your feet.

But there is one major difference that changes everything:

• Plantar fasciitis is usually a mechanical overload problem affecting the plantar fascia on the bottom of the foot, classically causing sharp “first-step pain” in the morning. ^[1]
• Tendonitis or tendinopathy is usually an overuse and degeneration process in a tendon, such as lateral elbow tendinopathy (tennis elbow), which is described as primarily degenerative rather than a classic inflammatory condition. ^{[2] [3]}
• Enthesitis is inflammation at the enthesis, the insertion site where a tendon, ligament, joint capsule, or fascia attaches to bone. It is considered a hallmark feature of spondyloarthritis conditions and can involve the Achilles tendon insertion and plantar fascia insertion. ^{[4] [5]}

Your best goal is not to self-diagnose. It is to recognize which pattern you most resemble, so you can choose the right first steps, avoid common mistakes, and know when you need a targeted work-up.

Pain driven by inflammation at an insertion point, often linked to inflammatory arthritis conditions such as spondyloarthritis and psoriatic arthritis. Common sites include the Achilles insertion and plantar fascia insertion, but many other insertions can be affected. ^{[4] [5]}

Pain from a tendon overload injury. In lateral epicondylitis (tennis elbow), tissue findings often reflect a degenerative overuse process with micro-tearing and disorganized collagen rather than classic inflammatory cell infiltration. ^[2]

Pain from overload and micro-injury of the plantar fascia. A classic hallmark is sharp heel pain with the first steps out of bed that may ease as you move and then worsen later with prolonged activity. ^[1] [6]

Before location and tests, focus on how the pain behaves.

• Morning stiffness that lasts a while and improves as you move
• Pain that improves with gentle activity and worsens with prolonged rest
• Multiple sites over time (for example, heel pain plus elbow insertion pain, plus knee tendon insertion pain)
• A personal or family history of psoriasis, inflammatory bowel disease, or inflammatory back pain
• Episodes of a red painful eye (uveitis) or swollen fingers/toes (dactylitis), depending on the broader pattern

Enthesitis is strongly linked with spondyloarthritis disease patterns, which is why clinicians take these systemic clues seriously. ^[5]

• Pain started after a clear training increase, new job demands, poor footwear, or repeated gripping/lifting
• Pain is most intense with loading (standing, running, gripping) and improves with rest
• Pain localizes to a specific structure and stays there, rather than “migrating”
• No systemic inflammatory symptoms

Mechanical patterns are still real and can be severe—but the treatment emphasis is usually load management and rehabilitation, not immune-directed therapy.

Heel pain is where confusion peaks, because both plantar fasciitis and enthesitis can be described as “insertion pain,” and both can be worse in the morning.

People with plantar fasciitis often describe:

• sharp pain at the inferior and medial heel
• pain worse with the first few steps out of bed
• pain that may improve after walking a bit, then worsen later after prolonged activity. ^[1]

This “first-step pain” pattern is so common that it is a core diagnostic clue in major clinical references on plantar fasciitis and plantar heel pain.^[1] [6]

Where it hurts

• most often the bottom inner heel (medial calcaneal tubercle region).

What makes it worse:

• prolonged standing, long walks on hard floors, barefoot walking at home, unsupportive shoes. ^[1]

Achilles tendinopathy often presents as

• pain and thickening in the Achilles tendon
• Pain worsens with running, jumping, stairs, and pushing off
• morning stiffness can occur, the pain is often strongly load-dependent.

This is typically treated with progressive strengthening and load management.

Achilles enthesitis is pain where the Achilles attaches to the heel bone. In enthesitis, the enthesis is the target and inflammation can be present. Achilles insertion and plantar fascia insertion are recognized enthesitis locations. ^[4]

• heel pain plus other insertion pains (kneecap tendon insertion, elbow insertion, rib insertion discomfort)
• history of psoriasis, inflammatory bowel disease, or inflammatory back pain
• persistent tenderness right at the Achilles insertion rather than the bottom inner heel
• swelling at the back of the heel, sometimes with warmth

Because the plantar fascia itself is also an enthesis-like insertion structure, inflammatory enthesitis can overlap with plantar fascia pain—this is where exam and imaging become important. ^[4]

Elbow pain is another hotspot for mislabeling.

Lateral epicondylitis is commonly described as a degenerative overuse process involving the extensor carpi radialis brevis and common extensor tendon, with histologic findings that reflect tendinosis rather than classic inflammatory cell infiltration. ^[2]

Classic clues:

• pain on the outer elbow
• worse with gripping, lifting, turning a doorknob, shaking hands
• pain reproduced with resisted wrist extension or gripping maneuvers
• improves with rest and load modification, returns with overuse

If the pain is driven by enthesitis, you may notice:

• pain that feels deeper and more “inflammatory”
• more morning stiffness and pain after rest
• other enthesitis sites (heel, kneecap tendon insertion, rib insertion discomfort)
• known inflammatory disease background (psoriasis, inflammatory bowel disease)

Also important: lateral elbow pain is sometimes misdiagnosed as tennis elbow, and other conditions can mimic it. If symptoms do not match typical tennis elbow behavior or do not improve with appropriate rehabilitation, a broader differential matters. ^[7]

Most typical plantar fasciitis pain location

• bottom inner heel (inferior medial heel) with first-step pain in the morning. ^[1]

Most typical Achilles enthesitis pain location

• back of the heel at the Achilles insertion (right where tendon meets bone). ^[4]

Most typical tennis elbow pain location

• outer elbow near the lateral epicondyle, worsened by gripping and wrist extension. ^[2]

Enthesitis can involve many insertion points across the body, including Achilles and plantar fascia insertions, patellar tendon insertion sites, hip trochanter attachments, and finger tendon insertions. ^[4]

These checks are not a diagnosis. They help you communicate patterns that clinicians use.

1. Is the worst pain with the first steps in the morning?
   That strongly supports plantar fasciitis patterns, though overlap is possible. ^[1]
2. Is the pain mainly under the heel (bottom) or behind the heel (Achilles insertion)?
   Bottom-inner heel leans plantar fascia; back-of-heel insertion tenderness leans Achilles insertion involvement.
3. Does it improve after warm-up, then worsen with prolonged standing later?
   That “warms up then worsens later” arc is classic for plantar fasciitis. ^[1]

1. Does gripping reliably reproduce pain?
   That leans lateral elbow tendinopathy. ^[2]
2. Do you have morning stiffness or multiple insertion pains?
   That leans enthesitis patterns.

• point tenderness at the plantar fascia origin at the heel
• pain reproduced by dorsiflexing the toes (which stretches the plantar fascia)
• gait changes due to heel pain

Plantar heel pain clinical descriptions emphasize these features. ^[1] [6]

• pain with resisted movement that loads the tendon (for example, wrist extension for tennis elbow)
• tendon thickening or localized tenderness
• pain provoked by specific repetitive activities

The degenerative overuse framing is discussed in clinical references. ^[2] [3]

• focal tenderness right at the insertion point
• pain with compressing the enthesis
• sometimes swelling at the insertion
• a pattern of multiple enthesis sites and other inflammatory clues
  Enthesitis definitions and sites are well described in rheumatology references. ^{[5] [4]}

Most cases of plantar fasciitis or tennis elbow are diagnosed clinically. Imaging becomes useful when symptoms are atypical, severe, persistent, or when an inflammatory condition is suspected.

Ultrasound is widely used in enthesitis assessment and has evidence supporting validity and reliability, though standardization is an ongoing issue. ^[8] Ultrasonographic features of enthesitis can include thickening, hypoechogenicity, calcifications, erosions, and Doppler signal at the enthesis. ^[9]

A practical takeaway: if a clinician suspects enthesitis, they may use ultrasound (especially with Doppler) to look for active inflammatory changes rather than purely degenerative tendon changes. ^[9]

Magnetic resonance imaging can show bone marrow edema and soft tissue inflammation at entheses in inflammatory conditions and can help when diagnosis remains unclear. ^[10]

Because plantar fasciitis often reflects overload plus tight calf mechanics, first-line management typically includes:

• reducing aggravating load temporarily (less standing on hard floors, less running hills)
• supportive footwear and arch support (including at home if hard floors trigger pain)
• calf and plantar fascia stretching
• gradual strengthening of foot and lower-leg muscles
  The classic plantar fasciitis pattern and conservative management emphasis are described in clinical references. ^[1]

Early management usually focuses on:

• activity modification (reduce repeated gripping and heavy lifting temporarily)
• progressive strengthening and rehabilitation (often eccentric and isometric loading programs)
• ergonomics and technique adjustments

Clinical references emphasize that this is an overuse-related tendinopathy and most cases improve with conservative care over time. ^[2] [3]

If enthesitis is suspected, two parallel tracks matter:

1. Local care: load modification, targeted physical therapy, avoiding repetitive aggravation
2. Inflammatory screen: checking for associated inflammatory disease clues (psoriasis, inflammatory bowel disease, inflammatory back pain, uveitis history) and considering rheumatology evaluation if pattern fits

Enthesitis is a key feature within spondyloarthritis patterns, and persistent enthesitis can influence when targeted therapies are considered in related inflammatory arthritides. ^[11]

Mistake 1: Treating inflammatory enthesitis like simple overuse forever

If you have multi-site insertion pain, prominent morning stiffness, and inflammatory disease clues, endless rest, braces, and random injections can delay the correct diagnosis. Enthesitis can be the visible tip of an inflammatory disease pattern. ^[5]

Mistake 2: Stretching aggressively through sharp pain

Gentle stretching can help plantar fasciitis. But aggressive stretching into sharp pain can flare irritated tissue, especially in insertion problems.

Mistake 3: Repeated corticosteroid injections as the main long-term plan

In lateral elbow tendinopathy, injections may give short-term relief but have not shown long-term benefit in some reviews and can have downsides if used repeatedly. ^[3]

Mistake 4: Ignoring shoe and floor factors for heel pain

For plantar fasciitis patterns, barefoot walking on hard floors and unsupportive footwear are frequent aggravators, and ignoring them makes recovery much harder. ^[1]

Seek prompt medical evaluation if you have:

• inability to bear weight after an injury
• fever, a hot swollen joint, or spreading redness (possible infection)
• numbness, tingling, or weakness suggesting nerve involvement
• sudden “pop” with bruising and major loss of function (possible tendon rupture)
• heel pain with systemic inflammatory signs (multiple insertion sites, inflammatory back pain, psoriasis, inflammatory bowel disease)

If your heel pain is worst with the first steps in the morning and mainly under the heel:

Plantar fasciitis is more likely. Start with load reduction, supportive footwear, and a structured stretching and strengthening plan. ^[1]

If your heel pain is behind the heel at the Achilles insertion and you also have inflammatory clues:

Enthesitis becomes more likely. Consider evaluation for spondyloarthritis patterns and ask whether ultrasound could clarify inflammatory insertion changes. ^[9]

If your elbow pain is outer elbow pain tied tightly to gripping and lifting:

Lateral elbow tendinopathy becomes more likely, and a progressive rehab approach usually helps more than repeated passive treatments. ^[2]

If your pain “moves,” involves multiple insertion sites, and comes with morning stiffness

Enthesitis patterns deserve more attention, because enthesitis is strongly associated with inflammatory arthritis spectra and may need a combined local-plus-systemic plan. ^[5]

• Plantar fasciitis commonly causes sharp heel pain that is worst with the first steps out of bed and may ease with initial walking before worsening later with prolonged activity. ^[1]
• Tennis elbow and many tendon overuse problems are often degenerative tendinopathies rather than classic inflammatory tendonitis, and they respond best to load modification plus progressive rehabilitation. ^{[2] [3]}
• Enthesitis is inflammation at tendon or fascia insertion sites, commonly involving Achilles and plantar fascia insertions and strongly linked to spondyloarthritis patterns. ^{[5] [4]}
• Ultrasound (with Doppler) can help identify enthesitis features such as thickening, erosions, and Doppler signal at the enthesis when the diagnosis is unclear. ^[9]

References: