I have read the following two terms:
Do these two terms refer to the same medical condition? Assume these two terms refer to the same attachment (e.g., attachment to the lateral facet of the greater trochanter) and that they are used in radiologist reports of hip MRIs.
The statement the question refers to may possibly denote two different conditions at two different sites, and, for instance, translate to:
There are tiny calcium deposits where gluteus attaches to crest of pelvis, and there is mild tendinitis/inflammation where gluteus inserts to femur, upper leg bone.
In other words, the reference might say that there is injury yet no inflammation at (below) the crest of the pelvis (ilium) where the gluteus medius https://en.wikipedia.org/wiki/Gluteus_medius attaches broadly ("proximal insertion"), and there is an inflammatory process of the tendon of muscle which inserts (i.e. attaches) to the femur (upper leg bone), at the trochanter (ridge).
See, e.g., What is the difference between tendonitis and gluteal tendinopathy?
"Degradation" at the pelvic origin of the gluteus might have been differentiated from tendinopathy at the the femur side. Different findings at different locations at the same time – as different stages of one and the same syndrome which as a combined one, thus may not even be rare.
However, this interpretation of two different areas of two different pathological findings can practically be ruled out. Extensive internet research provided no results for any known "degradation" lest inflammation at the proximal insertion of the gluteus medius or, nor of the two other gluteus muscles.
In conclusion, both findings with utmost certainty refer to the same location, which is the distal insertion of the gluteus medius at the trochanter.
In fact, "degradation" with high probability refers to a post-inflammatory situation. When tendinitis has been overcome, fibroblasts take over and rebuild tissue in a way that makes it less flexible; in that respect tendon of gluteus does not differ from tissue of other muscles.
Refering to the question, „degradation“ and „tenditis“ do not denote the same finding, however with high probability refer to different stages of the same inflammatory process of tendon. In other word, tendon is partly still inflamed, not yet "degraded" by fibroblasts' rebuilding activity. The diagnosis seems to refer to two stages of one proces at one site.
Literature search provides few proofs, see, for instance: "...Gluteus medius, gluteus minimus, and iliopsoas tendinopathy was graded normal, tendinosis, low-grade partial tear, high-grade partial tear, or full thickness tear...." From this reference there may only be infered that inflammation might precede "degradation" in a gradual process of successive stages. See Chi et al., 2014, Prevalence and pattern of gluteus medius and minimus tendon pathology and muscle atrophy in older individuals using MRI
As question and comment suggest ambivalence in the words, inference from correct understanding of medical terminology must also be addressed.
The word „attachment“ may, even among professionals, be used in a broad sense, as a general term, including "insertion" (of tendon). In some books or texts the word "attachment" may be opposed to "insertion" to emphasize "origin" (attachment) opposed to "insertion" (there is no term that would correspond to "origin", like aim. Caveat: "insertion" may freely be used to denominate the attachment on the origin side). Thus, from the use of the term "attachment" cannot be infered the site of injury.
Anatomically, at the site of origin, the gluteus medius does not taper out and attach ( or „insert“, both verbs are being used as synonyms, as question and comment suggest) by means of a tendon but broadly combines to wider area of the ilium bone, just below the crest of the upper pelvic. If there were inflammation at that site the word „tend“-itis or tendopathy would not be appropriate, as there is no tendon to speak of, but broad attach-“ment“. As suggested above, that may insinuate findings at the pelvic insertion site which, as searches provided, can be ruled out (no known pathology of pelvic insertion).
Advanced search terms I used were "pathology proximal attachment of the gluteus,
results for pelvic insertion site seem rare.
About the inflammation preceding "degradation" see
Murphy et al. , Eurorad, Calcific tendonitis of gluteus maximus insertion
"1. Formulative: A portion of tendon undergoes fibrocartilagenous transformation due to an unknown trigger and chalk-like calcification is deposited in the transformed tissue. 2. Resting: Once the calcified deposit is formed it undergoes a resting phase that may or may not be painful. It may also cause mechanical symptoms at this stage. 3. Resorpitve: An inflammatory response follows due to increased vascularity at the site of the calcific deposit. Macrophages and multinucleate giant cells attempt to absorb the calcific deposit. At this stage the calcific deposit resembles toothpaste and may leak into adjacent tissues including bursae, causing painful symptoms. 4. Postcalcific: Once the calcific deposit has been resorbed, the collagen pattern of the tendon is reconstituted by fibroblasts."
About the basics see What is the origin and insertion of the gluteus medius muscle?
Conversely, the word „degradation“ might have been used colloquially in lack of the word „tenditis“ as there is no tendon at the broad site of origin. This is a possibility that had to be ruled out, by the fact that "tendinitis" opposed to non-inflammatory "degradation" may denote two different stages of one process at one (the distal) site.
„While the calcium is being deposited, you may feel only mild to moderate pain or possibly no pain at all. For some unknown reason, calcific tendonitis becomes very painful when the deposits are being reabsorbed, often constant and nagging.“ This is when fibrocytes replace regular tendon tissue by building up fibrous texture, search is on calcific tendinitis
References
iliac crest pain: may have no radiological findings
First entative search provided resources about the attachment of the muscle and about the issue if the term tendon instead of attachment is being used when there is a tapering form of muscle thus a tendon, or, if "attachment" allows to infer to the proximal, the origin, of the muscle.
About the gluteus medius tendinopathy see, e.g. Steward Medical Group
About gluteus medius tendonitis see, e.g., Cellaxys.com
About ruling out "fatty degeneration of gluteus" as possibly being found by radiology see Takaoka et al. Radiodensity measurement is feasible for evaluating fatty infiltration in hip abductors
