Only if it was that easy lol. In general we are all manual therapist but all look at things from slightly different perspectives due to the theory we learn by. Chiropractor specialise specifically to the spine but do treat peripheral joints, osteopaths are fairly general and can treat peripheral joints aswell and physiotherapy can treat spine, peripheral, muscle and tendon , and nerve . Like the other professions you tend to specialise in certain areas whether that be lower limb, spines, shoulders, RA, etc. but we always have that standard knowledge.
I won't define the specifics as will be controversial particularly as the theories are different between the professions and i don't want to get it wrong lol. All I will say is that there are good manual therapist and bad manual therapist and principally you need to find the best one. One element as a physiotherapist I can't agree on is that some professionals suggest that your hips, back, shoulders, etc. are out of alignment. If this was true, that is how you are and it would take a life time posture correction and exercises to change it. So the thought that they re-aligning the joint is a lot of rubbish in my opinion particularly as I have spoken with spinal surgeons who tried to mobilise the spine during spinal operation and it's physically impossible.
When they manipulate your back, hips, etc they are activating your pain relieving mechanism which can be up to 100 x more powerful than morphine hence why you get immediate relief after manipulation. The reality is exercise and maintaining a healthy lifestyle is very important. Therapist should in theory after manual therapy give you exercises to maintain and improve the mobility at the joint as the pain has been reduced. (This is dependent on the problem of course.) The 'click' you hear when your manipulated is not 100% known but the generally accepted theory is it is a build up of cavitaions (air bubbles) with in the joint.
It's far more technical than this and there are reason why certain joints need to be put into certain positions to mobilise/manipulate them but the there's the basics for what I would want to know as a patient.
Differences aside I did a load of research around this when I was at university and the differences between treatment by different manual therapists and it all suggests that it is down to the preference of the individual / patient. For example, people that are treated by a chiropractor for years and have good results will not get the same results from and osteopath or a physiotherapist if they decided to change. So there is an element of psychology that comes with treatment and the same with pain. An example of pain and the psychological influences is a study that found that people with tooth pain got a 50% reduction in pain once they had arranged their appointment to see the dentist. This is your way of knowing your doing the right thing and the comfort of knowing someone is going to make everything better, so in turn your pain is reduced.
So going to one or another is not wrong but I would say that if you have had treatment for more than 3-6 weeks and your pains haven't changed then I would stop with that professional and seek medical or specialist advice. Pain is also common after treatment sometimes but your therapist should let you know if it will. If they don't and you do on more than one occasion even if you tell them you probably should avoid treatment by that individual. Ideally you should get some resolve in the session and have an idea of what is going on from your therapist. Try to remember that with insidious pains that you've had for a while, most of what a manual therapist does is best guest work based on our medical knowledge and experience in reality we never know the true cause of gradual onset pain as there may be one cause or it might be secondary to multiple contributing factors or all of the above.
This is the beauty of working in the NHS because although the waiting times are not fantastic but the support is. The team works as one, if your stuck you can ask more experienced team members for their advice, we get regular training in current issues and common problems, and read and analyses new evidence for treatment and assessment. We also get training from specialist consultants in orthopaedics and rheumatology. Ultimately we have medical support on hand and if we don't get a change over a period of time depending on the condition we refer direct to a specialist to ensure, that if your symptoms aren't changing we are sending you to someone who can investigate further.
So don't worry which professional you see but as long as they are accredited and make your pain(s) better and are treating you effectively meaning you have a set period of treatment and your not treated for months on end.
So in my opinion see a physiotherapist. Lol