Visitors travel insurance for acute onset of pre-existing conditions

Travel insurance is coverage only for unexpected medical expenses while you are on a trip away from home. Some companies offer coverage for what they call "acute onset" of a pre-existing condition (excluding chronic or congenital disorders). This would be a life or life-style threatening situation that cannot wait to be taken care of when the trip is over.
It must be "acute" meaning that it came on suddenly and needs to be taken care of quickly (defined as within 24 hours of symptom onset). A "pre-existing condition" does not necessarily have to have been previously diagnosed. If it is reasonable to assume that this condition started in the patient before the start date of the insurance, then it will be considered pre-existing to the policy. Note that the exclusion for chronic (conditions that worsen over time) and congenital (conditions a person is born with) limit greatly the application of this exception.
If asthma is not considered chronic, then an emergency due to asthma could be covered by a policy which covers at least "acute onset" of pre-existing conditions. If a person requires regular medication and/or doctor visits for their asthma, this will NOT be covered and will have to be paid by the insured completely out of pocket.
Note that in the US, the same medications can differ widely in costs depending on the pharmacy you use and some medications (generally generics) for common illnesses can be purchased for $40 per month at the Walmart pharmacy (although there may be long wait times). Also, some drug companies have special "coupons" available online for some of their drugs. There are often "discount cards" available at pharmacies and other stores for prescriptions that are free to use.
These are all resources your visitor can use to avoid paying full price for costly required medications should they run out while they are in the US. Other countries may not require a prescription and may not be as costly to obtain. Having a prescription with you, however, may be a good idea to ease getting the medication and show authorities you are allowed to have it (in the case of regulated substances which can vary country to country).

No. When you purchase any of our travel insurance plans, they offer guaranteed coverage with no medical questions. However, be aware that they all exclude pre-existing medical conditions. So, please take any medications you use regularly or for flare ups of your conditions since these will not be covered by travel insurance.
As far as I know, arthritis cannot lead to a life-threatening situation, so will be excluded from coverage by short-term travel policies. If you are a frequent traveler and want major medical coverage in any country to which you travel, you can opt for global medical policies which will (after the first year, generally) cover all aspects of health costs.
You can Compare and buy Global health insurance policies. To apply for these policies, you will have to reveal your entire medical history and you are not guaranteed coverage. The application must go through underwriting and you can be approved, rejected, or approved with exclusions. In any case, you can opt out of the policy 10 days from your approval for no cost to you or simply reject the exclusions they require on the policy.
Note that these policies are best for people who want health insurance for a whole year, or better, longer. Once you are approved on the plan, you are guaranteed coverage year after year and the price is determined by your age group, not your individual medical history.
So, in the case of a global medical insurance application, you would have to declare your arthritis on the application and you may or may not be covered for that illness by the policy they offer you.

Absolutely, yes! Travel insurance is meant to cover you in the unlikely event of a sudden illness or accident while you are on your trip. Even if you have a pre-existing condition that complicates treatment, that is not relevant to the coverage for an unexpected illness or injury. Naturally, your pre-existing conditions themselves are excluded from coverage, so you should pack as much medication as you will comfortably need for your trip.

Yes. Any medical condition you have been diagnosed with or are being treated for will be considered pre-existing to a new travel policy. If you take regular medication for your condition, this will not be covered by the policy. However, should you, for example, have an accident and break a bone, this would be covered even if your condition may have made you a little more vulnerable to the break (unless you were being particularly reckless).
Accidents are generally always covered (car accidents are more complicated because if you were not at fault, the driver's insurance may cover part of your injuries) unless caused by intoxication.
So, even if you have osteoarthritis or some other pre-existing condition, you are still eligible for coverage by a travel insurance policy which will protect you from sudden illness or accident/injury while you are on your trip.

This is a tough question. And, unfortunately, the answer depends on where you are traveling to and from.
For people that are traveling to the US from abroad:
As a broker, I am not a medical professional, so I can only tell you this from the insurance side of the question. Generally speaking, the most common cause for heart attack as I understand it is due to plaque build up in the person's arteries. Since that build up happens slowly, over time, I think it's fair to say that it would NOT be covered by any travel health insurance.
This is because travel health insurance excludes pre-existing conditions from any coverage (even emergency coverage if they are chronic or congenital). So the answer for the common cause of heart attacks is NO. So, foreigners run a risk (hopefully a small one) when traveling here. Health insurance can still help with costs of accidents and other unexpected illnesses while on vacation.

However, the answer is be different for people who are US residents traveling abroad. US residents can purchase trip cancellation plans and some of those waive the pre-existing condition exclusion IF you purchase them within a short time of your initial trip deposit (that is the earliest date you pay for any portion of your trip). Check out trip cancellation plans. Notably, the GeoBlue student and travel plans also waive the pre-existing condition exclusion for people who had creditable prior insurance coverage, and these plans are only available to US residents with US domestic coverage.
And, for travel plans for US residents going abroad, some, like the Safe Travels Outbound plans, will cover pre-existing conditions IF they have been stable in the last 6 months (meaning there have been no changes, episodes, or changes to medication in that time frame). You can Compare Safe Travels Outbound Insurance plans.

No. Travel health insurance is meant to cover a sudden illness or accident, such as you get a stomach flu or you twist or break your ankle. Since arthritis is not a life-threatening illness, it will not be covered by a short-term travel plan. Should you require regular medications or ointments, you should bring them or purchase ointments available in the visiting country for your condition.
Some countries may not require prescriptions to purchase medications.
However, you should be cautious in using a new medication since there may be side-effects of concern. You may want to stick to what you know or consult with your own physician if you can.