Exhibit 99.1
                                                                    ------------

                           Explanation of Responses:


(1) The stockholders are Warburg, Pincus Ventures, L.P., a Delaware limited
partnership ("WPV"), and Warburg Pincus & Co., a New York general partnership
("WP"). The sole general partner of WPV is Warburg Pincus Partners LLC, a New
York limited liability company ("WPP"), whose managing member is WP. Warburg
Pincus LLC, a New York limited liability company ("WP LLC" and together with
WPV, WPP and WP, the "Warburg Pincus Entities"), manages WPV. Charles R. Kaye
and Joseph P. Landy are Managing General Partners of WP and Managing Members of
WP LLC and may be deemed to control the Warburg Pincus Entities. Messrs. Kaye
and Landy disclaim beneficial ownership of all shares held by the Warburg Pincus
Entities. Kewsong Lee, a director of Knoll, Inc., is a general partner of WP and
a managing director and member of WP LLC. All shares indicated as owned by Mr.
Lee are included because of his affiliation with the Warburg Pincus Entities. By
reason of such affiliation, Mr. Lee may be deemed to have an indirect pecuniary
interest within the meaning of Rule 16a-1 of the Securities Exchange Act of
1934, as amended (the "Exchange Act"), in an indeterminate portion of the shares
reported herein. Mr. Lee disclaims "beneficial ownership" of such shares within
the meaning of Rule 13d-3 under the Exchange Act.