The issue of a criterion standard for diagnosis with specific reference to painful gluteal tendinopathy.

Here is a X (Twitter) exchange between Tom Goom @tomgoom and myself November 25 and 26 2025. It relates directly to the core principles of diagnostic accuracy of clinical tests.

Tom Goom is a widely respected physiotherapist who focuses on running injuries. His November 24 post discusses how gluteal tendinopathy can mimic back and leg pain, stressing the importance of a detailed history and exam for accurate diagnosis. Here's the full content:

“Gluteal Tendinopathy can present with back and leg symptoms. A careful history and thorough examination can help confirm the diagnosis.

The post includes this image showing pain referral patterns from the gluteal region to the lower back, buttock, and lateral thigh/leg”

My Question to Tom Goom was:

“What is the criterion standard for diagnosis of painful gluteal tendinopathy? I have asked this question of Alison Grimaldi @alisongrimaldi recently (conference in Queenstown Sept 2025), and she responded that MRI / U/S i.e high tech imaging, is the best we have. What is your opinion?”

Tom Goom's response with copies to @DrJN_SportsMed and @alisongrimaldi was:

“Good question. My thoughts would be why use an invasive technique when there is a non-invasive test battery we can use. This is based on @alisongrimaldi’s excellent work in this area: https://bjsm.bmj.com/content/51/6/519.short “

My response to @tomgoom was:

“I am familiar with @alisongrimaldi 's work. Please read the question I posed carefully. Imaging provides information on pathology, not pain. The problem of false positives on imaging (asymptomatic findings) is a consequence of that difference.

The question to consider is: Against what standard (the criterion) are imaging results compared? Other imaging? like u/s compared to MRI? A circular and invalid reference.

The only criterion standard that directly tests a pain source is guided local anesthetic injection; either into the structure itself, or to the nerve(s) that supply the structure. Yes it is invasive but has at least, face validity. Imaging does not have that.

If we compared imaging resuts to LA injection we would then know the accuracy of imaging.

This methodology has evolved and developed over 40 years for spinal pain. It works. We know the diagnostic value of imaging results. Without specific examples, here is some of what we know in the lumbar spine:

1. Degenerative changes seen on imaging are not diagnostic of pain, but there is a proportionate increase in the prevalence of pain as degenerative changes are more prevalent

2. Imaging changes seen in the facet & SIJ joints are not useful diagnostically

3. Certain specific imaging findings are highly specific to pain elicted by direct & specific challenge to the intervertebral disc e.g. HIZ, Modic changes and recent fracture

4. The only diagnostic standards for SIJ and facet joint pain are controlled anesthetic blocks.

   
   

   Back to my question: what is the criterion standard for a painful gluteal tendinopathy? If imaging cannot be such a standard (it isn't), what is? How do you know if you are directing your treatment to a painful structure or just a coincidental finding? Are your treatment failures a consequence of incorrect diagnosis, or an ineffective treatment for the diagnosis of painful gluteal tendinopathy?

   
   

   These are the questions that only properly designed and conducted research can answer. There is no point in beautifully designed and meticulously conducted RCTs when you don't know if the majority of included cases actually have the condition the treatment targets. SRs of such wonderful RCTs are also meaningless.

   
   

   Diagnosis matters.