It's complicated, and it depends. It can be copyright infringement to make a drawing based on a photo that copies just the pose. But you could have a good "fair use" defense to a copyright infringement claim if, for example, the drawing is political and not commercial, and has a neutral or positive effect on the original work.
You can't extract a ruling from 1 case and generalize to a given situation, just as you can't get individualized, personal legal advice from an anonymous public forum like this one. This is general information, nothing more.
The Mannion case was a S.D.N.Y. case, as is the Shepard Fairey v. AP litigation, which is ongoing and is also about a painting made from a photo, turned into the very famous Obama "Hope" poster. IP law is constantly being refined as new media and new situations arise, so the answer to a copyright infringement question will always be "it depends."
Copyright infringement hinges on "substantial similarity," a necessarily subjective determination that has to be considered on a work-by-work, case-by-case basis.
There's no bright line, one-size-fits-all rule you can follow. If you're going to base a work on another work, you run the risk of being sued. Acknowledging the access to the work in question means that you have to have even less similarity to the work than if you had never accessed the work, so if you inadvertantly independently created a work that was substantially similar to an existing one, you could still be sued but you'd have a stronger "independent creation" defense.
Ultimately, if you intend to commercialize a painting or drawing based on a photo that someone else owns the copyright to, you better see your own lawyer.
I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
You should talk to a lawyer to share the specific facts about your picture.
It could be that your use of the pose is necessary and thus not a protectable element. For example if you wanted to draw a football player catching a ball and you copied the hand positions from a photo of a professional, you would probably not have a problem since there is actually a "proper" position for the hands when catching a football and you would not be able to draw that in an original way.
Another example might be using photos of a ballet dancer in specific poses to make drawings in a book on how to dance ballet.
However, the line of what are necessary elements and what are not will come down to the particular photo and drawings and that is why you should talk to a lawyer.
This is a very interesting question. While I confer with my colleagues that much depends on what your work ultimately takes from the "inspirational" photograph, I would argue that you can reproduce the pose in your own way. As you already seem familiar with Mannion, you know that:
"To prove infringement, a plaintiff with a valid copyright must demonstrate that: (1) the defendant has actually copied the plaintiff's work; and (2) the copying is illegal because a substantial similarity exists between the defendant's work and the protectible elements of plaintiff's."[fn24] "Actual copying" — which is used as a term of art to mean that "the defendant, in creating its work, used the plaintiff's material as a model, template, or even inspiration"[fn25] — may be shown by direct evidence, which rarely is available, or by proof of access and probative similarities (as distinguished from "substantial similarity") between the two works.
The Court then went on to elaborate upon the "protectible elements" of the work. The pose may be a protectible element. In which case, be very careful.
Here is your practical problem. Each case is different, and if your drawing is substantially similar to the pose in the photograph, it might constitute patent infringement. More importantly, in all likelihood the owner of the photograph would have a legitimate reason to sue you for infringement--even if you ultimately would win the case under the doctrine of "fair use" or by showing that your work is not "substantially similar". Copyright suits are expensive to defend---it is not unusual for legal fees alone to run to six or seven figures (you cannot defend a suit like this for a few thousand dollars). And if you are found liable for infringement, you could be liable for statutory, actual and punitive (willfulness) damages. Statutory damages for willful infringement can be up to $150,000 per work. Your practical problem this--unless you obtain permission in advance (in writing) from the owner of the photograph, there is nothing to prevent the owner of the photograph from suing you for copyright infringement. Even if you ultimately prevail in the case, your costs will be very high.
Why not be practical---try to obtain a license from the owner of the photograph before making your drawing. You may have to pay a license fee or royalty, but at least you will avoid the possibility of an expensive law suit. One of my main jobs as an IP lawyer is to help clients avoid litigation by negotiating reasonable terms of license agreements in situations like this.