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                                                                   EXHIBIT 10.13

                          REGISTRATION RIGHTS AGREEMENT

         THIS REGISTRATION RIGHTS AGREEMENT ("Agreement") dated as of August 31,
1999, is entered into by and among MPI HOLDINGS, L.L.C., a Delaware limited
liability corporation ("Carlyle"), GE CAPITAL EQUITY INVESTMENTS, INC., a
Delaware corporation ("GE Equity"), and EMPI, INC., a Minnesota corporation (the
"Company") (individually, a "Party" and collectively, the "Parties").

                                    RECITALS

         A.   Carlyle and GE Equity have each entered into a separate
Subscription Agreement with EI Merger Corp. ("Merger Sub") dated as of August
31, 1999 (the "Subscription Agreements") pursuant to which each of Carlyle and
GE Equity have subscribed for and agreed to purchase from Merger Sub, and Merger
Sub has agreed to issue and sell to each of Carlyle and GE Equity, shares of
common stock, par value $0.01 per share, of Merger Sub (the "Merger Sub Common
Stock").

         B.   As an inducement to and a condition of the purchase of shares of
Merger Sub Common Stock by Carlyle and GE Equity, the Parties are entering into
this Agreement.

         C.   Immediately after consummation of the transactions contemplated by
the Subscription Agreement, Merger Sub will be merged (the "Merger") with and
into the Company, and upon consummation of the Merger, the Company will become
the surviving corporation and the successor of Merger Sub.

         D.   Carlyle and GE Equity, who upon consummation of the transactions
contemplated by the Subscription Agreement and upon consummation of the Merger,
will be the holders of all of the outstanding shares of Common Stock, and deem
it in their best interests and in the best interests of the Company to provide
for the registration of shares of the Common Stock and desire to enter into this
Agreement in order to effectuate that purpose and to set forth their respective
rights and obligations in connection with their investment in the Company

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises and mutual agreements
set forth in this Agreement, and subject to the terms and, conditions stated
herein, the Parties hereby agree as follows:

                                   ARTICLE 1.
                                   DEFINITIONS

         1.1  Defined Terms. As used in this Agreement, the following
capitalized terms shall have the following meanings:

         "Business Days" means all days other than Saturday or Sunday or any day
on which banking institutions in New York, New York are authorized or obligated
by law to close.

         "Carlyle" means MPI Holdings, L.L.C., a Delaware limited liability
company.

         "Common Stock" means the capital stock of the Company, however
designated, which is not limited as to the amount of dividends, and which is not
limited as to the amount of distributions upon liquidation or dissolution of the
Company, and shall include, without limitation, the Company's presently
authorized shares of Common Stock, $.01 par value per share.

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         "Company" means Empi, Inc. a Minnesota corporation.

         "Exchange Act" means the Securities Exchange Act of 1934, as amended
from time to time.

         "GE Equity" means GE Capital Equity Investments, Inc., a Delaware
corporation.

         "NASD" means the National Association of Securities Dealers, Inc.

         "Person" means an individual, firm, partnership, limited liability
partnership, corporation, limited liability company, trust, incorporated or
unincorporated association, joint venture, joint stock company or a government
or agency or political subdivision thereof.

         "Piggy-Back Registration" means a registration pursuant to Section 3.1.

         "Prospectus" means the prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement with respect
to the terms of the offering of any portion of the Registrable Securities
covered by the Registration Statement and by all other amendments and
supplements to the prospectus, including post-effective amendments and all
material incorporated by reference in such prospectus.

         "Registrable Securities" means (a) all shares of Common Stock owned by
the Shareholders, and (b) any shares of Common Stock issued or issuable with
respect to such shares of Common Stock by way of a stock dividend or stock split
or in connection with a combination of shares, recapitalization, merger,
consolidation or reorganization; provided, however, that any such share or other
security shall be deemed to be a Registrable Security only if and so long as it
is a Transfer Restricted Security.

         "Registrable Expenses" shall have the meaning as set forth in Article
6.

         "Registration Statement" means any registration statement of the
Company which covers Registrable Securities pursuant to the provisions of this
Agreement, including the Prospectus, amendments and supplements to such
Registration Statement, including post-effective amendments, and all exhibits
and all material incorporated by reference in such Registration Statement.

         "Securities Act" means the Securities Act of 1933, as amended from time
to time.

         "SEC" means the Securities and Exchange Commission.

         "Shareholders" means Carlyle and GE Equity and any of their permitted
successors or assigns.

         "Shareholders Agreement" means the Shareholders Agreement dated the
date hereof, by and among Company and the Shareholders.

         "Transfer Restricted Securities" means securities acquired by the
holder thereof other than pursuant to an effective registration under Section 5
of the Securities Act or pursuant to Rule 144; provided that (i) a security that
may be sold by the holder pursuant to Rule 144 without regard to volume
limitations imposed thereby shall cease to be a Transfer Restricted Security and
(ii) a security that has ceased to be a Transfer Restricted Security cannot
thereafter become a Transfer Restricted Security.

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         "Underwritten Registration" or "Underwritten Offering" means a
registration in which securities of the Company are sold (whether by the Company
or by selling stockholders) to an underwriter for reoffering to the public.

                                   ARTICLE 2.
                      SECURITIES SUBJECT TO THIS AGREEMENT

         2.1  Registrable Securities. The securities entitled to the benefits of
this Agreement are the Registrable Securities.

         2.2  Holders of Registrable Securities. A Person is deemed to be a
holder of Registrable Securities whenever such Person owns Registrable
Securities or has the right to acquire such Registrable Securities, whether or
not such acquisition has actually been effected and disregarding any legal
restrictions upon the exercise of such right.

                                   ARTICLE 3.
                       DEMAND AND PIGGY-BACK REGISTRATION

         3.1  Demand Registration.

             (a)  Request for Registration by Holders of Registrable Securities.
At any time after 180 days following the closing of the Company's initial
Underwritten Offering of Common Stock of the Company pursuant to which shares of
Common Stock are sold for the benefit of the Company, if the Company receives
from the holders of at least 400,000 shares of the Registrable Securities a
written request that the Company effect any registration or qualification with
respect to the Registrable Securities, the Company will:

                  (1)  within ten (10) days of receipt of such a request, give
written notice of the proposed registration or qualification to all other
holders of Registrable Securities; and

                  (2)  as soon as practicable, use its best efforts to effect
such registration or qualification (including, without limitation, the execution
in the applicable Registration Statement of an undertaking to file require
post-effective amendments, appropriate qualification under the applicable blue
sky or other state securities laws and appropriate compliance with exemptive
regulations issued under the Securities Act and any other governmental
requirements or regulations) as may be so requested and as are reasonably
necessary to permit or facilitate the sale and distribution of all or such
portion of such holder's or holders' Registrable Securities as are specified in
such request, together with all or such portion of the Registrable Securities of
any other holder or holders joining in such request or the Company in the case
of primary Registrable Securities requested by the Company to be registered as
are specified in a written notice given to the Company within 20 days after the
date of such written notice from the Company pursuant to Section 3.1(a)(1);
provided, however that the Company will not be obligated to effect more than
five (5) such registrations.

         Notwithstanding anything to the contrary set forth in this Agreement,
the Company shall not be required to effect a Demand Registration within six
months after the effective date of any other Registration Statement filed by the
Company. In addition, notwithstanding anything to the contrary, if at the time
of any request to register Registrable Securities pursuant to this Section
3.1(a), the Company is actively engaging, with the prior approval of the
Company's Board of Directors, in an Underwritten Offering as to which holders of
Registrable Securities are eligible to include Registrable Securities pursuant
to Section 3.2 (subject to the limitations and restrictions set forth in such
Section 3.2) or is engaged in any other activity which, in the good faith
determination of the Board of Directors of the

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Company, would be adversely affected by the requested registration to the
substantial detriment of the Company, then the Company may at its option direct
(a "Directive") in writing within ten (10) days of receipt of such request that
such request be delayed (and, if a majority of the holders of Registrable
Securities initiating such request so elect, withdrawn) for a period not in
excess of six months from the date of such Directive, which right to delay a
request may be exercised by the Company not more than once in any twelve month
period.

        Subject to the foregoing provisions, the Company will file a
registration statement covering the Registrable Securities so requested to be
registered as soon as practicable, after receipt of the request or requests of
the initiating holders, and shall use its best efforts to cause such
registration statement and prospectus through which such Demand Registration is
effected to remain effective, (i) in the case of a firm commitment underwritten
public offering, until each underwriter has completed the distribution of all
securities purchased by it and (ii) in the case of any other offering, until the
earlier of the sale of all Registrable Securities covered thereby or 120 days
after the effective date thereof, it being understood and agreed that any Demand
Registration that does not remain effective for such applicable time periods
will not be counted as a "registration" for purposes of Section 3.1(a)(2).

             (b)  Effective Registration. A registration of Registrable
Securities will not count as a Demand Registration until it has become effective
and has remained effective for the applicable period specified in Section
3.1(a).

             (c)  Underwriter's Cutback. If the holder or holders of a majority
in number of the Registrable Securities to be registered in a Demand
Registration under this Section 3 (or the holder or holders who initiated the
Demand Registration) so elect, the offering of such Registrable Securities
pursuant to such Demand Registration shall be in the form of an Underwritten
Offering. In such event, if the managing underwriter or underwriters of such
offering advise the Company and the holders in writing that in their opinion the
Registrable Securities requested to be included in such offering is sufficiently
large so as to materially and adversely affect the success of the offering, the
Company will include in such registration (i) first, the Registrable Securities
requested to be included therein pursuant to Section 3.1(a), pro rata among the
holders of the Registrable Securities on the basis of the number of Registrable
Securities owned by such holders requested to be included in such registration
and (ii) second, the securities the Company proposes to sell, which in the
opinion of such underwriters (after taking into account the securities to be
sold pursuant to clause (i)) can be sold without having a material adverse
effect on the offering.

             (d)  Selection of Underwriters. If any Demand Registration pursuant
to this Section 3 is to be in the form of an Underwritten Offering, the
investment banker or bankers and manager or managers that will administer the
offering will be selected by holders of a majority in number of Registrable
Securities to be included in such offering; provided that such investment
bankers and managers must be reasonably satisfactory to the Company.

        3.2  Piggy-Back Registration. At any time after the initial Underwritten
Offering of the Common Stock of the Company, if the Company determines to file a
registration statement under the Securities Act relating to a proposed sale to
the public of shares of its shares of Common Stock (but excluding registrations
relating solely to employees' stock option or purchase plans or relating solely
to a transaction employing SEC Form S-4 or Form S-8 or successor Forms thereto),
either for its own account or the account of a security holder or holders, the
Company shall:

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             (a)  promptly give to each holder of Registrable Securities written
notice thereof (which will include, to the extent known at the time, a list of
the jurisdictions in which the Company intends to attempt to qualify such
securities under the applicable blue sky or other state securities laws, the
proposed offering price or price range, and the plan of distribution);

             (b)  include in such registration (and any related qualification
under blue sky laws or other compliance), and in any underwriting involved
therein, all the Registrable Securities specified in a written request or
requests, made within 25 days after such written notice from the Company, by any
holder or holder of Registrable Securities; and

             (c)  use its best efforts to cause the managing underwriter or
underwriters of such proposed Underwritten Offering to permit the Registrable
Securities requested to be included in the registration statement for such
offering to be included on the same terms and conditions as any similar
securities of the Company included therein. Notwithstanding the foregoing, if in
the reasonable opinion of the managing underwriter or underwriters of such
offering, the marketing considerations require a limitation on the number of
shares of Common Stock offered pursuant to any Registration Statement filed
under this Section, the Company will include in such registration (i) first, the
securities the Company proposes to sell, (ii) second, the Registrable Securities
requested to be included therein, which in the opinion of such underwriters
(after taking into account the securities to be sold pursuant to clause (i)) can
be sold without having a material adverse effect on the offering, pro rata among
the holders of the Registrable Securities on the basis of the number of
Registrable Securities owned by such holders requested to be included in such
registration. The Company will bear all Registration Expenses in connection with
such a Piggy-Back Registration. Notwithstanding anything to the contrary herein,
if in the reasonable opinion of the managing underwriter or underwriters of such
offering, the marketing considerations require that no shares of Registrable
Securities be included in such offering, then the Company may, after notice
thereof to the holders of Registrable Securities requested to be included in
such registration, proceed with such offering without including therein such
Registrable Securities.

                                   ARTICLE 4.
                              HOLD-BACK AGREEMENTS

        4.1  Restrictions on Public Sale by the Holders of Registrable
Securities. Each holder of Registrable Securities agrees, if requested in
writing by the managing underwriters in an Underwritten Offering, not to effect
any public sale or distribution of securities of the Company of the same class
as the securities included in such Registration Statement, including a sale
pursuant to Rule 144 under the Securities Act (except as part of such
Underwritten Registration), during the 180-day period following the effective
date of the Registration Statement.

                                   ARTICLE 5.
                             REGISTRATION PROCEDURES

        In connection with the Company's registration obligations pursuant to
Section 3.1 hereof, the Company will use its best efforts to effect such
registration to permit the sale of such Registrable Securities in accordance
with the intended method or methods of disposition thereof, and pursuant thereto
the Company will as expeditiously as possible:

<PAGE>

                  (a)  before filing a Registration Statement or Prospectus or
any amendments or supplements thereto, furnish to the holders of the Registrable
Securities covered by such Registration Statement and the managing underwriters,
if any, copies of all such documents proposed to be filed, which documents will
be made available for review by such holders and managing underwriters, and the
Company will not file any Registration Statement or amendment thereto or any
Prospectus or any supplement thereto to which the holders of a majority in
number of the Registrable Securities covered by such Registration Statement or
the underwriters, if any, shall reasonably object;

                  (b)  prepare and file with the SEC such amendments and
post-effective amendments to any Registration Statement, and such supplements to
the Prospectus, as may be reasonably requested by the holders of a majority of
the Registrable Securities covered by the Registration Statement or any managing
underwriter of Registrable Securities or as may be required by the rules,
regulations or instructions applicable to the registration form utilized by the
Company or by the Securities Act or otherwise necessary to keep such
Registration Statement effective for the applicable period and cause the
Prospectus as so supplemented to be filed pursuant to Rule 424 under the
Securities Act; and comply with the provisions of the Securities Act;

                  (c)  notify the selling holders of Registrable Securities and
the managing underwriters, if any, promptly, and (if requested by any such
Person) confirm such advice in writing,

                       (i)   when the Prospectus or any Prospectus supplement or
post-effective amendment has been filed, and, with respect to the Registration
Statement or any post-effective amendment, when the same has become effective,

                       (ii)  of any request by the SEC for amendments or
supplements to the Registration Statement or the Prospectus or for additional
information,

                       (iii) of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or the initiation of
any proceedings for that purpose,

                       (iv)  of the receipt by the Company of any notification
with respect to the suspension of the qualification of the Registrable
Securities for sale in any jurisdiction or the initiation or threatening of any
proceeding for such purpose, and

                       (v)   of the existence of any fact which results in the
Registration Statement, the Prospectus or any document incorporated therein by
reference containing an untrue statement of material fact or omitting to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading;

                  (d)  use best efforts to obtain the withdrawal of any order
suspending the effectiveness of the Registration Statement at the earliest
possible moment;

<PAGE>

                  (e)  if reasonably requested by the managing underwriter or
underwriters or a holder of Registrable Securities being sold in connection with
an Underwritten Offering, as promptly as practicable incorporate in a Prospectus
supplement or post-effective amendment such necessary information as the
managing underwriters and the holders of a majority in number of the Registrable
Securities being sold reasonably request to have included therein relating to
the plan of distribution with respect to such Registrable Securities, including,
without limitation, information with respect to the amount of Registrable
Securities being sold to such underwriters, the purchase price being paid
therefor by such underwriters and with respect to any other terms of the
underwritten (or best efforts underwritten) offering of the Registrable
Securities to be sold in such offering; and make all required filings of such
Prospectus supplement or post-effective amendment as promptly as practicable
after being notified of the matters to be incorporated in such Prospectus
supplement or post-effective amendment;

                  (f)  at the request of any selling holder of Registrable
Securities, furnish to such selling holder of Registrable Securities and each
managing underwriter, without charge, such number of conformed copies of the
Registration Statement and any post-effective amendment thereto, including
financial statements and schedules, all documents incorporated therein by
reference and all exhibits (including those incorporated by reference) as such
holder may reasonably request;

                  (g)  deliver to each selling holder of Registrable Securities
and the underwriters, if any, without charge, as many copies of the Prospectus
(including each preliminary prospectus) and any amendment or supplement thereto
as such Persons may reasonably request and the written consent of the Company to
the use of the Prospectus or any amendment or supplement thereto by each of the
selling holders of Registrable Securities and the underwriters, if any, in
connection with the offering and sale of the Registrable Securities covered by
the Prospectus or any amendment or supplement thereto;

                  (h)  in connection with any public offering of Registrable
Securities, register or qualify or cooperate with the selling holders of
Registrable Securities, the managing underwriters, if any, and their respective
counsel in connection with the registration or qualification of such Registrable
Securities for offer and sale under the securities or blue sky laws of such
jurisdictions as any seller or underwriter reasonably requests in writing and do
any and all other acts or things necessary or advisable to enable the
disposition in such jurisdictions of the Registrable Securities covered by the
Registration Statement; provided that the Company will not be required to
qualify generally to do business in any jurisdiction where it is not then so
qualified or to take any action which would subject it to general service of
process in any such jurisdiction where it is not then so subject;

                  (i)  cooperate with the selling holders of Registrable
Securities and the managing underwriters, if any, to facilitate the timely
preparation and delivery of certificates representing Registrable Securities to
be sold and, if not required by applicable law, not bearing any restrictive
legends; and enable such Registrable Securities to be in such denominations and
registered in such names as the managing underwriters may request at least two
business days prior to any sale of Registrable Securities to the underwriters;

                  (j)  use its best efforts to cause the Registrable Securities
covered by the applicable Registration Statement to be registered with or
approved by such other governmental agencies or authorities as may be necessary
to enable the seller or sellers thereof or the underwriters, if any, to
consummate the disposition of such Registrable Securities;

<PAGE>

                  (k)  if any fact contemplated by paragraph (c)(vi) above shall
exist, use its best efforts to prepare a supplement or post-effective amendment
to the Registration Statement or the related Prospectus or any document
incorporated therein by reference or file any other required document so that,
as thereafter delivered to the purchasers of the Registrable Securities, the
Prospectus will not contain an untrue statement of a material fact or omit to
state any material fact required to be stated therein or necessary to make the
statements therein not misleading;

                  (l)  use its best efforts to cause all Registrable Securities
covered by the Registration Statement to be listed on each securities exchange
on which similar securities issued by the Company are then listed if requested
by the holders of a majority in number of such Registrable Securities or by the
managing underwriters, if any;

                  (m)  not later than the effective date of the applicable
Registration Statement, provide a CUSIP number for all Registrable Securities
and provide the applicable trustees or transfer agents with printed certificates
for the Registrable Securities which are in a form eligible for deposit with
Depositary Trust Company;

                  (n)  with respect to an Underwritten Offering or other
transaction in which an investment banking firm significantly participates,
enter into customary agreements with investment bankers and underwriters
(including underwriting agreements in customary form) and take all other
appropriate actions that the underwriter or investment banker may reasonably
request in order to expedite or facilitate the disposition of such Registrable
Securities;

                  (o)  make available to a representative of the holders of a
majority in number of the Registrable Securities, any managing underwriter
participating in any disposition pursuant to such Registration Statement, and
any attorney or accountant retained by the sellers or managing underwriter, all
financial and other records, pertinent corporate documents and properties of the
Company, and cause the Company's officers, directors and employees to supply all
information reasonably requested (taking into account the number of Registrable
Securities held by the requesting holder of Registrable Securities) by any such
representative, underwriter, attorney or accountant in connection with the
registration, with respect to each at such time or times as the Company shall
reasonably determine; provided that any records, information or documents that
are designated by the Company in writing as confidential shall be kept
confidential by such Persons unless disclosure of such records, information or
documents is required by court or administrative order;

                  (p)  otherwise use its best efforts to comply with all
applicable rules and regulations of the SEC, and make generally available to its
security holders, earnings statements satisfying the provisions of Section 11
(a) of the Securities Act and Rule 158 promulgated thereunder;

                  (q)  cooperate and assist in any filings required to be made
with the NASD and in the performance of any due diligence investigation by any
underwriter (including any "qualified independent underwriter" that is required
to be retained in accordance with the rules and regulations of the NASD); and

                  (r)  promptly prior to the filing of any document which is to
be incorporated by reference into the Registration Statement or the Prospectus
(after initial filing of the Registration Statement) provide copies of such
document to counsel to the holders of Registrable Securities and to the managing
underwriters, if any, make the Company's representatives available for
discussion of such document and make such changes in such document prior to the
filing thereof as counsel for such selling holders or underwriters may
reasonably request.

<PAGE>

             The Company may require each seller of Registrable Securities as to
which any registration is being effected to furnish to the Company such
information regarding such Seller and the distribution of such securities as the
Company may from time to time reasonably request in writing.

             Each holder of Registrable Securities agrees by acquisition of such
Registrable Securities that, upon receipt of any notice from the Company of the
happening of any event of the kind described in paragraph (k) above, such holder
will forthwith discontinue disposition of Registrable Securities until such
holder's receipt of the copies of the supplemented or amended Prospectus
contemplated by paragraph (k) above, or until it is advised in writing by the
Company that the use of the Prospectus may be resumed, and has received copies
of any additional or supplemental filings which are incorporated by reference in
the Prospectus, and, if so directed by the Company, such holder will deliver to
the Company (at the Company's expense) all copies, other than permanent file
copies, then in such holder's possession, of the Prospectus covering such
Registrable Securities current at the time of receipt of such notice. In the
event the Company shall give any such notice, the time periods mentioned in
Section 4.1 hereof shall be extended by the number of days during the period
from and including the date of the giving of such notice to and including the
date when each seller of Registrable Securities covered by such Registration
Statement either receives the copies of the supplemented or amended prospectus
contemplated by paragraph (k) above or is advised in writing by the Company that
the use of the Prospectus may be resumed.

                                   ARTICLE 6.
                              REGISTRATION EXPENSES

             6.1  Registration Expenses. All expenses incident to the Company's
performance of or compliance with this Agreement will be paid by the Company,
regardless whether the Registration Statement becomes effective. The expenses to
be paid by the Company shall include, without limitation:

                  (a)  all registration and filing fees (including, without
limitation, with respect to filings required to be made with the NASD);

                  (b)  fees and expenses of compliance with securities or blue
sky laws (including, without limitation, fees and disbursements of counsel for
the underwriters in connection with blue sky qualifications of the Registrable
Securities and determination of their eligibility for investment under the laws
of such jurisdictions as the managing underwriters or holders of a majority of
the Registrable Securities being sold may designate);

                  (c)  printing (including, without limitation, expenses of
printing or engraving certificates for the Registrable Securities in a form
eligible for deposit with Depositary Trust Company and of printing
prospectuses), messenger, telephone and delivery expenses;

                  (d)  fees and disbursements of counsel for the Company;

                  (e)  fees and disbursements of all independent certified
public accountants of the Company (including, without limitation, the expenses
of any special audit and "cold comfort" letters required by or incident to such
performance);

                  (f)  fees and expenses of other Persons retained by the
Company; and

                  (g)  fees and expenses associated with any NASD filing
required to be made in connection with the Registration Statement, (all such
expenses being herein called "Registration Expenses").

<PAGE>

             Registration Expenses shall not include fees, discounts,
commissions or disbursements of underwriters, selling brokers, dealer managers
or similar securities professionals relating to the distribution of the
Registrable Securities or legal expenses of any Person other than the Company.

             6.2  Company Expenses. The Company will, in any event, pay its
internal expenses (including, without limitation, all salaries and expenses of
its officers and employees performing legal or accounting duties), the expense
of any annual audit, the fees and expenses incurred in connection with the
listing of the securities to be registered on each securities exchange on which
similar securities issued by the Company are then listed, rating agency fees and
the fees and expenses of any Person, including special experts, retained by the
Company.