The opinion of the Court was delivered by
This appeal implicates anew the application of the discovery rule to toll the running of the statute of limitations in a medical malpractice action.
Plaintiff, who was rendered paraplegic in October 1992 by an abscess that compressed her spine, enlisted the aid of three experts, none of whom identified any fault on the part of defendant Dr. Michael DeLisi. She nonetheless continued her investigation and eventually obtained the opinion of a fourth expert, who concluded in July 1995 that Dr. DeLisi’s negligent care contributed to plaintiffs paraplegia. Plaintiff amended her complaint in March 1996 to add Dr. DeLisi as a defendant. We must decide whether the discovery rule tolls the two-year statute of limitations for medical malpractice actions, N.J.SA. 2A:14-2, to preserve plaintiffs action against Dr. DeLisi.
The trial court held that the discovery rule tolled the running of the statute of limitations and that plaintiff therefore timely filed her amended complaint naming Dr. DeLisi as a defendant. The Appellate Division reversed, finding that plaintiff had knowledge of facts supporting a claim against Dr. DeLisi prior to receiving her supportive expert’s opinion and in fact harbored an early belief that Dr. DeLisi was at fault. We disagree and reverse the Appellate Division.
*48I
In 1987, plaintiff was involved in an automobile accident that resulted in a condition known as Reflex Sympathetic Dystrophy Syndrome. That condition caused plaintiff to suffer severe pain to the right side of her neck, upper right arm, back, and shoulders. In an attempt to alleviate plaintiffs pain, Dr. Philip Rubinfeld treated plaintiff with a series of thoracic epidural catheterizations.
On September 21, 1992, Dr. DeLisi admitted plaintiff to Dover General Hospital so that Dr. Rubinfeld could perform another catheterization. During that procedure, Dr. Rubinfeld experienced difficulty inserting the catheter and as a result punctured plaintiffs back numerous times. Eventually, another physician, Dr. Robert Lalli, assisted with the insertion. During plaintiffs subsequent four-day hospital stay, the sterile dressing holding her catheter in place remained unchanged despite the appearance of a dark-red drainage on the dressing. On September 25, 1992, the catheter was removed and plaintiff was discharged.
Within a week of her discharge, plaintiff began to experience numbness and tingling from the waist down and difficulty with urination and bowel movements. Dr. DeLisi ordered plaintiff readmitted to the hospital on October 1, 1992. Dr. Peter Heit, the admitting physician, diagnosed plaintiff with “urinary tract sepsis.” Plaintiff remained hospitalized that night and saw Dr. DeLisi on the following morning. At that time, plaintiff informed Dr. DeLisi that she was experiencing tingling, pain, and numbness in her legs. Dr. DeLisi did not diagnose plaintiff that morning.
Dr. DeLisi saw plaintiff again on the morning of October 3. At that time, plaintiff was having problems walking without assistance. Dr. DeLisi examined plaintiff, noticed pus at the site of the epidural catheter, and told her that “[s]omething went wrong with the thoracic epidural.” He diagnosed plaintiff with an epidural abscess and ordered her to the operating room for surgery to remove the abscess. The abscess, which was compressing plaintiffs spinal cord, was removed, but plaintiff did not regain the ability to walk.
*49Several days after plaintiffs surgery, Dr. Rubinfeld visited plaintiff in her hospital room. Plaintiff asked Dr. Rubinfeld whether he did anything wrong that might have caused her paraplegia. Plaintiff alleges that Dr. Rubinfeld responded: “No. But I wished they had called me when you were admitted----I would have known what went wrong and what steps to take. Things would have been done a lot faster.” Following a course of antibiotics, plaintiff was discharged from the hospital on November 2,1992.
In August 1994, before filing her complaint in the Law Division, plaintiff consulted Mervyn Jeffries, M.D. Dr. Jeffries concluded that plaintiffs health care providers were negligent during the insertion of the catheter, as well as during her first hospital stay in September. Dr. Jeffries did not give an opinion in respect of whether Dr. DeLisi deviated from accepted standards of care.
In September 1994, plaintiff filed a personal injury action against Dover General Hospital, Dr. Rubinfeld, and others involved with plaintiffs care during her September 1992 hospital admission. In December 1994 and April 1995, respectively, plaintiffs attorney consulted with two additional medical experts, Elliot Justin, M.D., and AiHo Kim, M.D. Specifically, plaintiffs attorney inquired of those two experts whether the treatment plaintiff received during her admission in October of 1992 deviated from accepted standards of care, causing her paralysis. Neither expert concluded that Dr. DeLisi or any other post-epidural care provider was negligent. In July 1995, plaintiffs counsel contacted a fourth expert, Richard Hetherington, M.D., who concluded that Dr. DeLisi’s delay in diagnosing the epidural abscess was a contributing factor to plaintiffs paraplegia.
Plaintiff amended her complaint in March 1996 to add Dr. DeLisi as a defendant. Dr. DeLisi filed a motion for summary judgment, asserting that plaintiffs amended complaint was time-barred by the statute of limitations. Dr. DeLisi alleged that plaintiff knew of facts sufficient to trigger the running of the statute of limitations in respect of a claim against him as early as *50September or October 1992. The trial court granted Dr. DeLisi’s motion, stating that plaintiff had sufficient information to alert her that Dr. DeLisi’s delay in diagnosing her epidural abscess may have contributed to her paraplegia. The court therefore held that the discovery rule did not apply to toll the running of the statute of limitations. Following dismissal of plaintiffs action against Dr. DeLisi, Dr. Lalli, whom plaintiff had also named as a defendant, retained the services of an expert who concluded that Dr. DeLisi’s negligence caused or contributed to plaintiffs paraplegia. Accordingly, Dr. Lalli filed a third-party complaint against Dr. DeLisi.
In February 2000, we decided companion cases, Mancuso v. Neckles, 163 N.J. 26, 747 A.2d 255, and Gallagher v. Burdette-Tomlin Memorial Hospital, 163 N.J. 38, 747 A.2d 262. In those cases, the plaintiffs initially relied on expert advice indicating that third-party physicians were not at fault, but later heard from experts who indicated the contrary. We applied the discovery rule in both cases and permitted the plaintiffs to amend their complaints to name those additional physicians as defendants.
Following our decisions in Mancuso and Gallagher, plaintiff filed a motion for reconsideration of the trial court’s 1997 order granting summary judgment for Dr. DeLisi. In ruling on the motion, the trial court cited Mancuso and Gallagher, as well as plaintiffs earlier reliance on the opinions of Drs. Jeffries, Justin, and Eim. It concluded that plaintiff reasonably did not become aware of Dr. DeLisi’s negligence at the time of her injury and that therefore the statute of limitations for a cause of action against Dr. DeLisi did not begin to run until plaintiffs fourth expert, Dr. Hetherington, provided his opinion to plaintiff. The trial court granted plaintiffs motion for reconsideration and vacated its earlier grant of summary judgment for Dr. DeLisi. It then dismissed Dr. Lalli’s third-party complaint against Dr. DeLisi without prejudice to facilitate the filing of this appeal.
The Appellate Division granted Dr. DeLisi leave to appeal. The panel agreed with Dr. DeLisi’s argument that plaintiff “was well aware at an early date of the facts supporting her claim against *51Mm.” It eoncMded that plaintiffs “knowledge of the facts and her belief that [Dr. DeLisi] bore some responsibility are sufficient to bar application of the discovery rule.” The panel reversed the vacation of summary judgment and remanded the matter for an order dismissing plaintiffs complaint against Dr. DeLisi. This Court granted plaintiff leave to appeal. 172 N.J. 174, 796 A.2d 891 (2002).
II
Because it is “mequitable that an rnjured person, unaware that he has a cause of action, should be denied his day m court solely because of his ignorance, if he is otherwise blameless,” Lopez v. Swyer, 62 N.J. 267, 274, 300 A.2d 563 (1973), New Jersey courts long have employed the equitable principle of the discovery rule to avoid the potentially harsh effects of the “mechanical application” of statutes of limitations. Vispisiano v. Ashland Chem. Co., 107 N.J. 416, 426, 527 A.2d 66 (1987). The discovery rule delays accrual of a cause of action “until the injured party discovers, or by an exercise of reasonable diligence and rntelligenee should have discovered[,] that [he or she] may have a basis for an actionable claim.” Lopez, supra, 62 N.J. at 272, 300 A.2d 563. To start the statute of limitations running in a case involving “complex medical causation,” in which “it is not at all self-evident that the cause of injury was ‘the fault of ... a third party,’ ” Mancuso, supra, 163 N.J. at 34, 747 A.2d 255 (quoting Vispisiano, supra, 107 N.J. at 434, 527 A.2d 66), “more is required than mere speculation or an uninformed guess ‘without some reasonable medical support’ that there was a causal connection” between the plaintiffs condition and the third party’s conduct. Ibid, (quotmg Vispisiano, supra, 107 N.J. at 437, 527 A.2d 66).
Although the discovery rule does not require “knowledge of a specific basis for legal liability or a provable cause of action,” it does require “knowledge not only of the injury but also that another is at fault.” Martinez v. Cooper Hosp.-Univ. Med. Ctr., 163 N.J. 45, 52, 747 A.2d 266 (2000) (citations omitted). Accord*52ingly, plaintiffs who seek application of the discovery rule may be “divided into two classes: those who do not know that they have been injured and those who know they have suffered an injury but do not know that it is attributable to the fault of another. A cause of action does not accrue until both of those factors exist.” Id. at 53, 747 A.2d 266. This Court also has distinguished a “subcategory” of that second genre of “knowledge of fault” cases, which includes actions brought by plaintiffs who “know[] [they have] been injured and [that] the injury was the fault of another, but do[] not know that a third party was also responsible for [their] plight.” Id. at 54, 747 A.2d 266.
“[W]hen a plaintiff knows of an injury and that the injury is due to the fault of another, he or she has a duty to act.” Caravaggio v. D'Agostini, 166 N.J. 237, 249-50, 765 A.2d 182 (2001). However, when that plaintiff reasonably remains unaware that an additional third party also may be at fault, “the accrual clock does not begin ticking against the third party until the plaintiff has evidence that reveals [the third party’s] possible complicity.” Id. at 250, 765 A.2d 182. In the two recent decisions factually analogous to the instant appeal, Mancuso, supra, and Gallagher, supra, this Court permitted the plaintiffs to amend their complaints to name additional physicians as defendants more than two years subsequent to the dates they sustained their injuries. In both cases, the plaintiffs had relied on earlier expert opinions indicating that the additional physicians were not at fault.
In Mancuso, supra, we held that “when a patient has relied on competent expert advice that one or more of her treating physicians did not contribute to the patient’s injuries, later assertions to the contrary by a competent expert would then provide the ‘basis for an actionable claim.’ ” 163 N.J. at 37, 747 A.2d 255 (quoting Lopez, supra, 62 N.J. at 272, 300 A.2d 563). The plaintiff in Mancuso was a breast cancer victim whose cancer remained undiscovered for three years after her radiologist erroneously diagnosed a cyst in her breast as benign. Id. at 30, 747 A.2d 255. An expert retained by the plaintiff alleged that the plaintiffs *53surgeon was negligent, but did not indicate any fault on the part of the plaintiff’s radiologist. Id. at 32, 747 A.2d 255. We held that until the production of a defense expert’s report indicating fault on the part of the radiologist, the “nature of the information” possessed by the plaintiff did not suggest that the spread of her breast cancer might have been due to the radiologist’s negligence. Id. at 35, 747 A.2d 255. Thus, we found that “the ‘quality of the requisite state of mind’ that she possessed appeared blameless.” Ibid. The plaintiff “did not suspect, much less have reason to believe, that she may have been injured by the conduct of [the radiologist].” Ibid. Accordingly, we applied the discovery rule to preserve the plaintiffs claims against the radiologist.
In Gallagher, supra, the plaintiff was rendered completely incontinent by surgery intended to correct an incontinence problem. The plaintiff timely filed suit against the hospital, the surgical team, and various fictitious defendants, but failed to name her after-care physicians as defendants. 163 N.J. at 41, 747 A.2d 262. Several years after she sustained her injuries, plaintiff was alerted, through the deposition of a defense expert, that her aftercare urologists may have been responsible for her injuries. Id. at 42, 747 A.2d 262. Until that time, she had relied on her own experts’ reports that did not indicate any malpractice on the part of those individuals. Id. at 41, 747 A.2d 262. Applying the discovery rule analysis set forth in Mancuso, we concluded that the plaintiff “had no reasonable basis to suspect that her crippling condition was caused by anything other than the original surgery ...,” that the plaintiff exercised “ ‘reasonable diligence and intelligence’ in asserting her claim ..and that there was “[n]o readily apparent indication of [the after-care urologists’] potential contribution to the patient’s medical deterioration ... until [a defense expert] brought the failure to treat plaintiffs infection to light.” Id. at 41, 44, 747 A.2d 262 (quoting Lopez, supra, 62 N.J. at 272, 300 A.2d 563). Accordingly, we applied the discovery rule to preserve the plaintiffs claims.
*54III
Dr. DeLisi contends that the discovery rule should not apply because plaintiff knew or reasonably should have known that she had a basis for a claim against him at the time of her injury or shortly thereafter. In support of that assertion, he cites portions of plaintiffs answers to Dr. Rubinfeld’s interrogatories, including allegations that “medical personnel failed to properly diagnose [her] injuries [and] failed to take effective measures and to provide timely medical treatment,” as well as statements that indicate her knowledge of the chronology of her care during her October admission and Dr. DeLisi’s role in providing that care. We note, however, that plaintiff provided those interrogatory answers in July 1995, the same month that Dr. Hetherington supplied plaintiff with his expert opinion that Dr. DeLisi deviated from accepted standards of care. Dr. DeLisi provides no basis for concluding that plaintiff had support for her assertions independent of Dr. Hetherington’s report.
Dr. DeLisi also cites Dr. Rubinfeld’s statements that had he been called when plaintiff was admitted to the hospital in October, he “would have known what went wrong and what steps to take,” and “[t]hings would have been done a lot faster,” as evidence that plaintiff knew or reasonably should have known of the existence of her claim against Dr. DeLisi. Although Dr. Rubinfeld’s comments may suggest obliquely that Dr. DeLisi’s delay in ordering surgery may have contributed to plaintiffs paraplegia, his statements are too vague and self-serving to constitute “reasonable medical support” for a claim against Dr. DeLisi. Mancuso, supra, 163 N.J. at 34, 747 A.2d 255. At most, Dr. Rubinfeld’s statement imposed on plaintiff a “duty to act,” that is, to investigate whether there might be a cause of action against any of her after-care providers. Caravaggio, supra, 166 N.J. at 250, 765 A.2d 182. She fulfilled that duty, as evidenced by her consultation with numerous experts and her specific inquiries in respect of whether the care she received during her October 1992 hospital admission deviated from accepted standards. Plaintiff was not “dilatory.” Mancuso, su*55pro, 163 N.J. at 36, 747 A.2d 255. As in Mancuso and Gallagher, plaintiff reasonably relied on earlier expert advice indicating an absence of fault on the part of a particular defendant. Accordingly, we do not find that plaintiff knew or reasonably should have known of the existence of her claim against Dr. DeLisi.
In deciding whether to apply the discovery rule, we also must consider whether Dr. DeLisi has been “unfairly prejudiced.” Id. at 37, 747 A.2d 255 (citing Lopez, supra, 62 N.J. at 276, 300 A.2d 563). As a third-party defendant impleaded by Dr. Lalli, Dr. DeLisi has been an active participant in this case, represented by counsel, for nearly five years. He is already conversant with the facts and issues that would be litigated by plaintiff and has participated in discovery and depositions. Dr. DeLisi has not suggested that the passage of time has made any evidence or witnesses unavailable. We therefore conclude that Dr. DeLisi is not prejudiced by application of the discovery rule in this appeal.
In view of plaintiffs reasonable reliance on the expert advice she received prior to consulting with Dr. Hetherington, as well as the absence of undue prejudice to Dr. DeLisi, we conclude that the discovery rule applies to preserve plaintiffs claim. We add only our disagreement with the dissent’s conclusion that our decision endorses an open-ended process that allows a plaintiff an indefinite period in which to search for an expert willing to support a preferred theory of liability. First, in this appeal, as in Mancuso and Gallagher, plaintiff reasonably relied on expert advice indicating an absence of fault on the part of a particular care provider. In the majority of medical malpractice cases, such detrimental reliance is unlikely. Second, when, as in this appeal, litigation against other defendants already is in progress, the time limitations prescribed in our court rules will serve to limit a plaintiffs ability to continue the search for a supportive expert. When no litigation is pending, the discovery rule’s inquiry into diligence by the plaintiff and prejudice to the defendant will accomplish the same objective. Finally, the discovery rule is a doctrine of equity and there is nothing in our jurisprudence that would bar the *56application of other equitable principles such as unclean hands or laches to avoid undue prejudice to a potential defendant.
IV
We reverse the Appellate Division and remand the matter to the Law Division to reinstate the June 2000 order that vacated the 1997 summary judgment order in favor of Dr. DeLisi.