Sec Form 3 Filing - LSV Associates II, LLC @ SHOULDER INNOVATIONS, INC. - 2025-07-30

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person LSV Associates II, LLC 2. Issuer Name and Ticker or Trading Symbol SHOULDER INNOVATIONS, INC. [ SI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 420 BOYLSTON ST., SUITE 602 3. Date of Earliest Transaction (MM/DD/YY) 07/30/2025 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series C Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,096,971 I See Footnotes ( 2 ) ( 3 ) Series D Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 521,499 I See Footnotes ( 2 ) ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other LSV Associates II, LLC 420 BOYLSTON ST. SUITE 602 BOSTON, MA02116 X Lightstone Ventures II, L.P. 420 BOYLSTON ST. SUITE 602 BOSTON, MA02116 X Lightstone Ventures II (A), L.P. 420 BOYLSTON ST. SUITE 602 BOSTON, MA02116 X Plain Henry A JR 420 BOYLSTON ST. SUITE 602 BOSTON, MA02116 X George Jean 420 BOYLSTON ST. SUITE 602 BOSTON, MA02116 X Signatures Lightstone Ventures II, L.P., By: LSV Associates II, LLC, its general partner, By: /s/ Henry Plain, Managing Director 07/30/2025 Signature of Reporting Person Date Lightstone Ventures II (A), L.P., By: LSV Associates II, LLC, its general partner, By: /s/ Henry Plain, Managing Director 07/30/2025 Signature of Reporting Person Date LSV Associates II, LLC By: /s/ Henry Plain, Managing Director 07/30/2025 Signature of Reporting Person Date /s/ Henry Plain 07/30/2025 Signature of Reporting Person Date /s/ Jean George 07/30/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Immediately prior to the closing of the Issuer's initial public offering, the shares of preferred stock of the Issuer will automatically convert into shares of Common Stock on a one-for-0.052410901 basis. The shares of preferred stock have no expiration date. ( 2 )Consists of (i) 1,036,638 shares of Common Stock underlying Series C Preferred Stock, and 492,833 shares of Common Stock underlying Series D Preferred Stock held by Lightstone Ventures II, L.P. ("LSV II"); and (ii) 60,333 shares of Common Stock underlying Series C Preferred Stock and 28,666 shares of Common Stock underlying Series D Preferred Stock held by Lightstone Ventures II (A), L.P. ("LSV II (A)"). LSV Associates II, LLC is the general partner of LSV II and LSV II (A) and has sole voting and dispositive power with respect to the shares held by LSV II and LSV II (A). Jean George, Michael A. Carusi and Henry A. Plain, Jr. are the managing directors of LSV Associates II, LLC, and share voting and dispositive power with respect to the shares held of record by LSV II and LSV II (A). ( 3 )Mr. Carusi is a director of the Issuer and files separate Section 16 reports. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his, her or its respective pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.