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                                                                     Exhibit 5.1








                                          December 11, 2001



dj Orthopedics, LLC
DJ Orthopedics Capital Corporation
dj Orthopedics, Inc.
2985 Scott Street
Vista, California 92083

                       REGISTRATION STATEMENT ON FORM S-1

Ladies and Gentlemen:

         We have acted as special counsel to dj Orthopedics, LLC (the
"Company"), DJ Orthopedics Capital Corporation ("DJ Capital" and, together with
the Company, the "Issuers") and dj Orthopedics, Inc. in connection with the
registration statement on Form S-1 (the "Registration Statement") relating to
market-making activities with respect to $100 million aggregate principal amount
of the Issuers' 12 5/8% Senior Subordinated Notes due 2009 (the "Notes"). The
Notes are guaranteed (the "Guarantee") by dj Orthopedics, Inc., as successor in
interest to DonJoy, L.L.C. The Notes and the Guarantee of DonJoy, L.L.C. were
originally issued in December 1999 in exchange for a like principal amount of
the Issuers' 12 5/8% Senior Subordinated Notes due 2009 (the "Old Notes") in an
exchange offer (the "Exchange Offer") previously registered on Form S-4 (File
Nos. 333-86835, 333-86835-01 and 333-86835-02).

         We have examined originals or copies, certified or otherwise identified
to our satisfaction, of such documents, corporate records, certificates of
public officials and other instruments as we have deemed necessary or advisable
for the purpose of rendering this opinion, including, without limitation, the
following: (a) the certificate of incorporation or formation, operating or
limited liability company agreement and by-laws of dj Orthopedics, Inc., DonJoy,
L.L.C. and the Issuers; (b) the Certificate of Merger filed on November 20, 2001
by DonJoy, L.L.C. with the Secretary of State of the State of Delaware in
connection with the merger (the "First Merger") consummated on such date
pursuant to the Agreement and Plan of Merger dated October 26, 2001 among dj
Orthopedics, Inc., DJ Acquisition Corporation ("DJ Acquisition") and DonJoy,
L.L.C. (the "First Merger Agreement"); (c) the Certificate of Merger filed on
November 20, 2001 by dj Orthopedics, Inc. with the Secretary of State of the
State of Delaware in connection with the merger (the "DonJoy Merger" and,
together with the First Merger, the "Mergers") consummated on such date pursuant
to the Agreement and Plan of Merger dated November 7, 2001 (the "DonJoy Merger
Agreement" and, together with the First Merger

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dj Orthopedics, LLC
DJ Orthopedics Capital Corporation
dj Orthopedics, Inc.
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Agreement, the "Merger Agreements") between dj Orthopedics, Inc. and DonJoy,
L.L.C.; (d) the Indenture dated as of June 30, 1999 (the "Indenture") among the
Issuers, dj Orthopedics, Inc., as successor in interest to DonJoy, L.L.C., and
The Bank of New York, as Trustee, relating to the Notes and the Guarantee; (e)
the corporate and limited liability company proceedings of dj Orthopedics, Inc.,
the Issuers, DonJoy, L.L.C. and DJ Acquisition related to, among other things,
the Mergers, the Exchange Offer, the authorization, execution and delivery of
the Merger Agreements and the Indenture, and the issuance of the Notes and the
Guarantee; and (f) the Merger Agreements. As a result of the DonJoy Merger,
DonJoy, L.L.C. was merged with and into dj Orthopedics, Inc. which was the
surviving entity of the DonJoy Merger.

         Upon the basis of the foregoing, we are of the opinion that:

         1)  The Notes have been duly authorized and, assuming the Notes
             were duly executed, authenticated and delivered in accordance
             with the Indenture in exchange for the Old Notes in accordance
             with the Indenture and the Exchange Offer, the Notes are valid
             and binding obligations of the Issuers enforceable against the
             Issuers in accordance with their terms, subject to applicable
             bankruptcy, insolvency, reorganization, moratorium, fraudulent
             conveyance and similar laws affecting creditors' rights
             generally and subject to general principles of equity.

         2)  Assuming the due execution, authentication and delivery of the
             Notes in accordance with the Indenture in exchange for the Old
             Notes in accordance with the Indenture and the Exchange Offer,
             as a result of the DonJoy Merger the Guarantee is the valid
             and binding obligation of dj Orthopedics, Inc. enforceable
             against dj Orthopedics, Inc. in accordance with its terms,
             subject to applicable bankruptcy, insolvency, reorganization,
             moratorium, fraudulent conveyance and similar laws affecting
             creditors' rights generally and subject to general principles
             of equity.

         We are members of the Bar of the State of New York and the foregoing
opinions are limited to the laws of the State of New York, the General
Corporation Law of the State of Delaware and the Limited Liability Company Act
of the State of Delaware.

    We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. We also consent to the reference to us under the caption
"Legal Matters" in the prospectus contained in such Registration Statement. In
giving this consent, we do not thereby admit that we are included in the
category of persons whose consent is required under Section 7 of the Securities
Act of 1933, as amended, or the rules and regulations promulgated thereunder.


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dj Orthopedics, LLC
DJ Orthopedics Capital Corporation
dj Orthopedics, Inc.
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    This opinion is rendered solely to you in connection with the above
matter. This opinion may not be relied upon by you for any other purpose or
relied upon by or furnished to any other person without our prior written
consent.

                                           Very truly yours,


                                           /s/ O'Sullivan LLP