Agree with all that is posted here and wanted to add that joint pain - as opposed to pain from long bones like legs and arms - is not what they refer to with MPN bone pain. If the pain is in both knees, both elbows etc. It could be RA - which tends to affect joints on both sides of the body at the same time. I get some of each of these types of pain - but the ET bone pain is mostly achy, comes and goes, and so far hasn't been too bad. People with MPNs often also develop other autoimmune diseases like RA - so keep an eye on that because some meds can help RA. I don't really notice a pattern to my pain but do think heat (hot weather) might make my bone pain worse. I am thinking that makes sense since ice(cold) reduces inflamation.

I remembered there is an article on this website, so this is the link for this:
https://www.mympnteam.com/resources/pain-and-mp...

I found a clear and simple explanation of why we experience bone pain in MPNs:
"In normal people bone marrow is confined to the central skeleton (cranium, ribs, sternum, vertebrae, and pelvis). The long bones contain mostly fat. In MPN, the bone marrow expands outward to the long bones and can be seen even out in the fingers and toes when bone marrow scanning is done.
The proliferation within the bone marrow cavity may cause pressure inside the bone that, in turn, causes inflammation of the covering of the bone (periostium).
The resulting periostitis may be painful. In some patients with bone and joint pain treatment with myelosuppressive therapy has decreased or eliminated these symptoms by reducing the amount of bone marrow in the cavity and reducing the pressure that it causes."
https://www.pvreporter.com/bone-joint-pain-mpn-...

And there are studies on abdominal and bone pain as symptoms present in MPNs:
"Chronic pain (abdominal, bone) is a prevalent and undermanaged feature of MPN disorders. Chronic non-MPN pain is further complicated by the development of the disorder. Many MPN patients lack understanding on its prevalence and furthermore feel ill-equipped to manage it. Patients have, however, found symptomatic benefit from various pharmacological and non-pharmacological treatment modalities that require further exploration. Results from this study suggest MPN patients should be assessed regularly for pain and offered early referral to specialized services for evaluation, source identification and treatment."
https://www.sciencedirect.com/science/article/p...

I hope this helps understanding this issue more.

Pain and MPNs: Causes and Management | myMPNteam

https://www.mympnteam.com/resources/pain-and-mpns-causes-and-management

Bone & Joint Pain In MPN Patients Explained | Proliferative | PV Reporter

https://www.pvreporter.com/bone-joint-pain-mpn-explained/

Thank you, Tta, for such great references and information. It’s very helpful! Lydia ~ thank you for your insight as well. I had a strange pain in my upper left arm/shoulder last year that would randomly come and and go, & several MDs couldn’t confirm the cause. I originally thought it might have been related to my basic workout program (yet I never had an issue before). I now believe it may be related to my ET. Whenever it pops up now ~ which thankfully seems to be less frequently ~ taking Advil liqui-gels seems to eliminate it.

Bone pain is just that, a sort of dull pain in tibia or other leg or arms/shoulder bones, similar to the pain people feel when taking Neulasta, a drug that stimulates the bone marrow to make leukocytes, only that in people with ET, genetic mutations lead to the bone marrow overproduction of platelets. This can lead to swelling of bone marrow and pain, irrespective of risk category, meaning low-risk ET patients can experience bone pain too. Most times the bone pain in ET is not as severe as with Neulasta.
For me it feels like a serious tooth ache-like pain in lower leg bones (e.g., tibia),
sometimes the femur hurts, and sometimes shoulders and arms bones are also painful.
If often comes after one does effort above what their body can handle. It just feels like a sort of bone inflammation, if one can imagine that. Not joint, but the bone itself.
Given that this is due to ET, once other causes are excluded, such as fracture, osteoporosis or autoimmunity, etc., then that is that.
As treatment for ET depends on thrombotic risk, it is unlikely that a doctor would give treatment only because one has bone pain.
What helps me is pacing, not doing more than what my body can handle, and rest. Sometimes a bit of paracetamol.
Both my dad and my granny had high levels of platelets and had bone pain, so it might be something specific to the type of mutation one has. Some mutations are more likely to trigger inflammation, and from mutation to mutation, different mechanisms seem to be involved in this.
Given that all MPNs involve chronic inflammation, this type of pain can be maintained also by the overall chronic inflammation in the body.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC46...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC77...

Impact of Inflammation on Myeloproliferative Neoplasm Symptom Development

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4619953/

KEY ROLE OF INFLAMMATION IN MYELOPROLIFERATIVE NEOPLASMS: INSTIGATOR OF DISEASE INITIATION, PROGRESSION. AND SYMPTOMS

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7746200/

In response to your question about bone pain, thirty-three years ago I had breast cancer. The treatment was surgery and 6 chemo treatments three weeks apart if my blood counts were ok. About the 5th treatment, I had deep aching pains in my arms. I knew instinctively it was due to the treatments. I dont think I ever asked the doctor about it as I was working, recovering from surgery and dealing with having a family. I have ET and Jac2 mutation and have been taking hydroxyurea and aspirin for almost a year. Seems like my symptoms are cyclical, severe fatigue for a while, now starting with body aches, so far no bone pain. My experience was a deep aching pain in my arms between shoulder and elbow. To me that would mean it was in the bone marrow. I know that is not scientific but being emotionally and self aware is an important skill to have in this life. Just my experience. GOD bless you in your journey.