Exhibit 3.281

CERTIFICATE OF INCORPORATION

OF

RIVERSIDE HOSPITAL, INC.

I, the undersigned natural person acting as an incorporator of a corporation (hereinafter called the “Corporation”) under the General Corporation Law of Delaware, do hereby adopt the following Certificate of Incorporation for the Corporation:

FIRST: The name of the Corporation is Riverside Hospital, Inc.

SECOND: The registered office of the Corporation in the State of Delaware is located at 32 Loockerman Square, Suite L-100, in the City of Dover, County of Kent. The name of the registered agent of the Corporation at such address is The Prentice-Hall Corporation System, Inc.

THIRD: The purpose for which the Corporation is organized is to engage in any and all lawful acts and activity for which corporations may be organized under the General Corporation Law of Delaware. The Corporation will have perpetual existence.

FOURTH: The total number of shares of stock which the Corporation shall have authority to issue is 1,000 shares, par value $1.00 per share, designated Common Stock.

FIFTH: The name of the incorporator of the Corporation is Stanley F. Baldwin, and the mailing address of such incorporator is 3333 Lee Parkway, P. O. Box 650398, Dallas, Texas 75265-0398.

SIXTH: The number of directors constituting the initial board of directors is one and the names and mailing address of the person who is to serve as the director until the first annual meeting of stockholders or until his successors are elected and qualified are Stanley F. Baldwin, 3333 Lee Parkway, P. O. Box 650398, Dallas, Texas 75265-0398.

SEVENTH: Directors of the Corporation need not be elected by written ballot unless the bylaws of the Corporation otherwise provide.

EIGHTH: The directors of the Corporation shall have the power to adopt, amend, and repeal the bylaws of the Corporation.

NINTH: No contract or transaction between the Corporation and one or more of its directors, officers, or stockholders or between the Corporation and any person (as used herein “person” means other corporation, partnership, association, firm, trust, joint venture, political subdivision, or instrumentality) or other organization in which one or more of its directors, subdivision, or instrumentality) or other organization in which one or more of its directors, officers, or stockholders are directors, officers or stockholders, or have a financial interest, shall be void or voidable solely for this reason, or solely because the director or officer is present at or participates in the meeting of the board or committee which authorizes the contract or transaction, or solely because his, her, or their votes are counted for such purpose, if: (1) the

material facts as to his or her relationship or interest and as to the contract or transaction are disclosed or are known to the board of directors or the committee, and the board of directors or committee in good faith authorizes the contract or transaction by the affirmative votes of a majority of the disinterested directors, even though the disinterested directors be less than a quorum; or (2) the material facts as to his or her relationship or interest and as to the contract or transaction are disclosed or are known to the stockholders entitled to vote thereon, and the contract or transaction is specifically approved in good faith by vote of the stockholders; or (3) the contract or transaction is fair as to the Corporation as of the time it is authorized, approved or ratified by the board of directors, a committee thereof, or the stockholders. Common or interested directors may be counted in determining the presence of a quorum at a meeting of the board of directors or of a committee which authorizes the contract or transaction.

TENTH: The Corporation shall indemnify any person who was, is, or is threatened to be made a party to a proceeding (as hereinafter defined) by reason of the fact that he or she (i) is or was a director or officer of the Corporation, is or was serving at the request of the Corporation as a director, officer, partner, venturer, proprietor, trustee, employee, agent, or similar functionary of another foreign or domestic corporation, partnership, joint venture, sole proprietorship, trust, employee benefit plan, or other enterprise, to the fullest extent permitted under the Delaware General Corporation Law, as the same exists or may hereafter be amended. Such right shall be a contract right and shall include the right to be paid by the Corporation expenses incurred in defending any such proceeding in advance of its final disposition to the maximum extent permitted under the Delaware General Corporation Law, as the same exists or may hereafter be amended. If a claim for indemnification or advance meet of expenses hereunder is not paid in full by the Corporation within sixty (60) days after a written claim has been received by the Corporation, the claimant may at any time thereafter bring suit against the Corporation to recover the unpaid amount of the claim, and if successful in whole or in part, the claimant shall also be entitled to be paid the expenses of prosecuting such claim. It shall be a defense to any such action that such indemnification or advancement of costs of defense are not permitted under the Delaware General Corporation Law, but the burden of proving such defense shall be on the Corporation. Neither the failure of the Corporation (including its board of directors or any committee thereof, independent legal counsel, or stockholders) to have made its determination prior to the commencement of such action that indemnification of, or advancement of costs of defense to, the claimant is permissible in the circumstances nor an actual determination by the Corporation (including its board of directors or any committee thereof, independent legal counsel, or stockholders) that such indemnification or advancement is not permissible shall be a defense to the action or create a presumption that such indemnification or advancement is not permissible. In the event of the death of any person having a right of indemnification under the foregoing provisions, such right shall inure to the benefit of his or her heirs, executors, administrators, and personal representatives. The rights conferred above shall not be exclusive of any ;other right which any person may have or hereafter acquire under any statute, bylaw, resolution of stockholders or directors, agreement, or otherwise.

The Corporation may additionally indemnify any employee or agent of the Corporation to the fullest extent permitted by law.

As used herein, the term “proceeding” means any threatened, pending, or completed action, suit, or proceeding, whether civil, criminal, administrative, arbitrative, or investigative, any appeal in such an action, suit, or proceeding, and any inquiry or investigation that could lead to such an action, suit, or proceeding.

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ELEVENTH: No holder of any shares of capital stock of the Corporation, whether now or hereafter authorized, shall, as such holder, have any preemptive or preferential right to receive, purchase, or subscribe to (a) any unissued or treasury shares of any class of stock (whether now or hereafter authorized) of the Corporation, (b) any obligations, evidences of indebtedness, or other securities of the Corporation convertible into or exchangeable for, or carrying or accompanied by any rights to receive, purchase, or subscribe to, any such unissued or treasury shares, (c) any right of subscription to or to receive, or any warrant or option for the purchase of, any of the foregoing securities, or (d) any other securities that may be issued or sold by the Corporation.

TWELFTH: The personal liability of the directors of the corporation is hereby eliminated to the fullest extent permitted by paragraph (7) of subsection (b) of §102 of the General Corporation Law of the State of Delaware as the same may be amended and supplemented, except for liability (i) for any breach of the director’s duty of loyalty to the Corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or knowing violation of law, (iii) under Section 174 of the Delaware General Corporation Law, or (iv) for any transaction from which the director derived an improper personal benefit. Any repeal or amendment of this Article Twelfth by the stockholders of the Corporation shall be prospective only, and shall not adversely affect any limitation on the personal liability of a director of the Corporation arising from an act or omission occurring prior to the time of such repeal or amendment. In addition to the circumstances in which a director of the Corporation is not personally liable as set forth in the foregoing provision of this Article Twelfth, a director shall not be liable to the Corporation or its stockholders to such further extent as permitted by any law hereafter enacted, including, without limitation, any subsequent amendment to the Delaware General Corporation Law.

THIRTEENTH: Whenever a compromise or arrangement is proposed between this corporation and its creditors or any class of them and/or between this corporation and its stockholders or any class of them, any court of equitable jurisdiction within the State of Delaware may, on the application in a summary way of this corporation or of any creditor or stockholder thereof or on the application of any receiver or receivers appointer for this corporation under the provisions of §291 of Title 8 of the Delaware Code or on the application of trustees in dissolution or of any receiver or receivers appointed for this corporation under the provisions of §279 of Title 8 of the Delaware Code order a meeting of the creditors or class of creditors, and/or of the stockholders or class of stockholders of this corporation, as the case may be, to be summoned in such manner as the said court directs. If a majority in number representing three fourths in value of the creditors or class of creditors, and/or of the stockholders or class of stockholders of this corporation, as the case may be, agree to any compromise or arrangement and to any reorganization of this corporation as consequence of such compromise or arrangement, the said compromise or arrangement and the said reorganization shall, if sanctioned by the court to which the said application has been made, be binding on all the creditors or class of creditors, and/or on all the stockholders or class of stockholders, of this corporation, as the case may be, and also on this corporation.

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I, the undersigned, for the purpose of forming the Corporation under the laws of the State of Delaware, do make, file, and record this Certificate of Incorporation and do certify that the facts stated herein are true and, accordingly, I do hereunto set my hand on this 19^th day of April, 1991.

/s/ Stanley F. Baldwin

Stanley F. Baldwin, Incorporator

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