The opinion of the Court was delivered by

LONG, J.

The discovery rule, incorporating as it does a notion of simple justice, has been anything but simple in application, as evidenced by the amount of litigation it has spawned. Decades after its enunciation, lawyers and judges are still grappling with its application. This is another such case.

I

Plaintiff Patricia Caravaggio and her husband were seriously injured in a motorcycle accident on May 23, 1993. Mrs. Caravaggio's specific injury was a segmental fracture of the femur, also called the thighbone. She was taken by ambulance to Morristown Memorial Hospital where the defendant, Dr. Robert D'Agostini, an orthopedic surgeon, performed surgery to repair the bone. Dr. D'Agostini "reamed out" Mrs. Caravaggio's femur bone, inserted a rod manufactured by the Synthes Corporation in the hollow of the bone, and affixed the rod with screws through the bone at both ends to stabilize the fracture.

Mrs. Caravaggio was discharged from the hospital and underwent physical therapy at home, remaining under the care of Dr. D'Agostini who had previously explained to her that she could expect an average healing time of twelve weeks, and that among the complications possible were "infection, blood clots, blood loss or anemia, failure to heal, need for rod removal later, rod breakage." On June 15, 1993, Dr. D'Agostini modified the physical therapy prescription to permit as much weight-bearing on the injured leg as Mrs. Caravaggio could tolerate. On July 13, 1993, Dr. D'Agostini told Mrs. Caravaggio to increase the vigor of her physical therapy, noting that she should continue to use crutches and to bear weight on her injured leg. Two weeks later on July 28, 1993, Mrs. Caravaggio felt a "snap" in her leg while the physical therapist was bending her knee.

Dr. D'Agostini examined Mrs. Caravaggio at his office on August 4, 1993. An x-ray of the leg revealed that the rod had broken through the screw holes. Dr. D'Agostini told Mrs. Caravaggio that he was "very much surprised" that a rod manufactured by Synthes, "probably the best manufacturer of rods in the world", could break in eight weeks. According to D'Agostini,

I have had . . . totally irresponsible people throw away their crutches, walk on these things and they never break.

. . .

I was shocked that the thing broke and so I told them [the Caravaggios] that was surprising. They were, as I — they can characterize their recollections, but it's my recollection that they were, you know, more mad at the physical therapist, that it had been the vigor or physical therapy bending the knee.

And I told them no, that that was not the case. That the physical therapist was doing what I told them to do and that in any case no single bend, no human being could take that rod and snap it, no physical therapist with a rod inside somebody's leg could cause that rod to snap unless there was something structurally wrong with it. (emphasis added).

Dr. D'Agostini explained to Mrs. Caravaggio that her injuries would now take longer to heal and could require additional surgery to replace the rod. First, however, he recommended bracing and conservative treatment to attempt to avoid additional surgery. Mrs. Caravaggio accepted his recommendation. She continued with follow-up visits, but by September 28, 1993, the doctor determined that her femur would not heal without further surgery.

In early October, Mrs. Caravaggio obtained a second opinion from an orthopedist for insurance purposes. That physician agreed with Dr. D'Agostini's recommendation of surgery and, although he indicated that perhaps Dr. D'Agostini might have chosen a thicker rod to implant, did not suggest directly or obliquely that Mrs. Caravaggio should question the medical care she received from Dr. D'Agostini. Mrs. Caravaggio continued in Dr. D'Agostini's care and he performed the second surgery on October 21, 1993, to replace the broken rod. In that surgery, he "reamed" the femur bone more extensively and inserted a thicker and longer rod.

After the second surgery, Dr. D'Agostini informed Mrs. Caravaggio that there was something wrong with the rod and that she should take it to the lawyer who was representing her in her lawsuit against the operator of the car that struck her. The rod was then sent to the hospital's pathology lab, and at some later date (not determined with specificity in the record) the rod was given to the attorney representing Mrs. Caravaggio in her ongoing auto negligence litigation.

After Mrs. Caravaggio's discharge, in May of 1994, her husband continued to be treated by Dr. D'Agostini well into the fall of 1995, over two and one-half years from the accident. During that period, Mr. and Mrs. Caravaggio both referred family and friends to him.

In the meantime, on July 28, 1994, Mrs. Caravaggio's counsel sent the rod to be analyzed by J. Stephen Duerr, President of Metuchen Analytical. Metallurgic tests revealed that the rod was not defective. The record is unclear exactly when that information was received, although it was certainly after July 1994.

In late 1994 or early 1995, Mrs. Caravaggio met a new attorney who suggested that she might have a medical malpractice claim. She retained that attorney who, in turn, referred her to her present counsel, who filed a complaint on her behalf against Dr. D'Agostini on September 15, 1995.

Dr. D'Agostini moved for summary judgment, arguing that Mrs. Caravaggio's complaint was barred by the expiration of the two year statute of limitations. The trial court ordered a discovery rule hearing as required by Lopez v. Swyer, 62 N.J. 267 (1973). After the hearing, at which the facts related in this opinion were established and presumably viewed in a light most favorable to Mrs. Caravaggio pursuant to R. 4:46-2(c), the court granted the motion, concluding that Mrs. Caravaggio knew or should have known that she had an actionable claim against Dr. D'Agostini no later than August 4, 1993:

[P]laintiff knew she suffered an injury on July 28 or 29, 1993. At that time she believed that the injury was caused by the physical therapist and she expressed that opinion to defendant on August 4, 1993, when she learned that the rod had broken.

. . .

Arguably, defendant's statement may have "lulled" plaintiff into believing that the wrongdoer was neither the physical therapist nor the defendant, because implicit in defendant's statement was an assurance that the physical therapy defendant ordered was actually proper.

Nevertheless, the court concluded that because Mrs. Caravaggio knew she was injured on August 4, 1993, and that "the injury was the product of someone's wrongdoing," summary judgment was appropriate because her cause of action accrued on that date and her complaint was filed two years and fifty-two days later.

The Appellate Division affirmed the trial court's judgment because "the judge's factual findings and conclusions of law [on the statute of limitations issue] are supported by sufficient evidence in the record and the applicable law." Caravaggio v. D'Agostini, No. A-91-98T5, slip op. at 4 (App.Div. November 15, 1999). According to the Appellate Division, and based on statements she made to Dr. D'Agostini about the physical therapist, Mrs. Caravaggio knew on August 4, 1993 that she had been wrongfully injured and that someone should be held accountable. We granted Mrs. Caravaggio's petition for certification on January 28, 2000, 164 N.J. 560 (2000), limited solely to the statute of limitations issue. We now reverse.

II

N.J.S.A. 2A:14-2 gives a plaintiff a two year period from the accrual of his or her claim in which to file a malpractice action. At common law, there was no limit on the time in which a plaintiff could institute such litigation. Rothman v. Suber, 90 N.J. Super. 22 (App.Div. 1966) (citing Uscienski v. National Sugar Refining Co., 19 N.J. Misc. 240, 242 (C.P. 1941)). Since then, statutes of limitations have been adopted regarding all causes of action, in order to "promote repose by giving security and stability to human affairs." Wood v. Carpenter, 101 U.S. 135, 139, 25 L.Ed. 807 (1879). Their purpose is to

penalize dilatoriness and serve as measure of repose. * * * When a plaintiff knows or has reason to know that he has a cause of action against an identifiable defendant and voluntarily sleeps on his rights so long as to permit the customary period of limitations to expire, the pertinent considerations of individual justice as well as the broader considerations of repose, coincide to bar his action. Where, however, the plaintiff does not know or have reason to know that he has a cause of action against an identifiable defendant until after the normal period of limitations has expired, the considerations of individual justice and the considerations of repose are in conflict and other factors may fairly be brought into play.

[Farrell v. Votator Div. of Chemetron Corp., 62 N.J. 111, 115 (1973); Fernandi v. Strully, 35 N.J. 434, 438 (1961).]

The latter principle is embodied in the so-called "discovery rule." Vispisiano v. Ashland Chemical Co., 107 N.J. 416 (1987). The purpose behind the rule

"is to avoid harsh results that otherwise would flow from mechanical application of a statute of limitations." [Vispisiano, supra, 107 N.J. at 426]. Accordingly, the doctrine "postpon[es] the accrual of a cause of action" so long as a party reasonably is unaware either that he has been injured, or that the injury is due to the fault or neglect of an identifiable individual or entity. Id. at 426-27; accord Lynch v. Rubacky 85 N.J. 65, 70 (1981); Lopez, supra, 62 N.J. at 274. Once a person knows or has reason to know of this information, his or her claim has accrued since, at that point, he or she is actually or constructively aware "of that state of facts which may equate in law with a cause of action." Burd v. New Jersey Tel. Co., 76 N.J. 284, 291 (1978).

[Abboud v. Viscomi, 111 N.J. 56, 62-63 (1988).]

"The linchpin of the discovery rule is the unfairness of barring claims of unknowing parties." Mancuso v. Neckles, 163 N.J. 26, 29 (2000).

In Baird v. American Med Optics, 155 N.J. 54 (1998), we articulated that principle more fully:

Critical to the running of the statute is the injured party's awareness of the injury and the fault of another. Savage v. Old Bridge-Sayreville Medical Group, P.A. 134 N.J. 241, 243 (1993). The discovery rule prevents the statute of limitations from running when injured parties reasonably are unaware that they have been injured, or, although aware of an injury, do not know that the injury is attributable to the fault of another. Tevis v. Tevis, 79 N.J. 422, 432 (1979).

[Id. at 66.]

The question in a discovery rule case is whether the facts presented would alert a reasonable person, exercising ordinary diligence, that he or she was injured due to the fault of another. The standard is basically an objective one — whether plaintiff "knew or should have known" of sufficient facts to start the statute of limitations running. Baird, supra, 154 N.J. at 72.

That does not mean that the statute of limitations is tolled until a plaintiff has knowledge of a specific basis for legal liability or a provable cause of action. Savage v. Old Bridge-Sayreville Medical Group, P.A. 134 N.J. 241, 248 (1993). It does, however, require knowledge not only of the injury but also that another is at fault. Id. at 246; Lynch, supra, 85 N.J. at 70. Both are critical elements in determining whether the discovery rule applies. For that analysis, it has been held that plaintiffs are to be divided into 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. Lopez, supra, 62 N.J. at 274. When a plaintiff's claim falls within the latter class her cause of action does not accrue until she has knowledge of the injury and that such injury is the fault of another.

In many cases, knowledge of fault is acquired simultaneously with knowledge of injury. Fault is apparent, for example, where the wrong tooth is extracted during surgery. Tramutola v. Bortone, 118 N.J. Super. 503, 512-13 (App.Div. 1972), or where a foreign object has been left within the body after an operation. See Fernandi, supra, 35 N.J. at 438 (holding that period of limitations on a patient's negligence cause of action began to run when the patient knew or had reason to know about the foreign object left in her body). In other cases, however, a plaintiff may be aware of an injury but not aware that the injury is attributable to the fault of another.

In Lopez, supra, 62 N.J. at 271, for example, the plaintiff suffered from severe burns, pain, and nausea after undergoing radiation therapy following a radical mastectomy for breast cancer. Plaintiff's husband had previously been told by a physician that "this was not malpractice. This sometimes happens." Lopez v. Swyer, 115 N.J. Super. 237, 244 (App.Div. 197 1). While Ms. Lopez was being treated for her symptoms by another doctor, she overheard him say to colleagues, "[a]nd there you see, gentlemen, what happens when the radiologist puts a patient on the table and goes out and has a cup of coffee." Lopez, supra, 62 N.J. at 271. The Appellate Division reversed the trial court's grant of summary judgment for the radiologist, and this Court affirmed. Although Ms. Lopez knew that her burns were caused by the radiation therapy, the record did not reveal that she knew or should have known, prior to overhearing the "cup of coffee" statement, of the causal connection between her physician's negligent treatment and her injury. Thus her complaint, filed slightly over five years after her injury, but within two years of the "cup of coffee" statement, was ruled timely.

Likewise, in Lynch, supra, 85 N.J. at 67-68, the plaintiff injured her ankle and was operated on by the defendant. When she did not improve and suffered great pain and disability, the defendant continually assured her that her condition was due to the original injury and the healing process. It was not until after the statute of limitations expired that another physician suggested that the plaintiff's problem was due to the defendant's negligence. Id. at 69. We held that "all of the factors

militating against adequate knowledge of physician fault" were present in the case. Id. at 77. Included were the plaintiff's faith in the defendant, his reassurances that the pain and swelling were part of the healing process, and the fact that a physician who the plaintiff later consulted did not suggest the defendant's medical negligence until after the statute had run. Ibid. We thus held her action to be timely.

"A sub-category of the 'knowledge of fault' cases is that in which a plaintiff knows she has been injured and knows the injury was the fault of another, but does not know that an additional party was also responsible for her plight." Martinez v. Cooper Hosp. 163 N.J. 45, 54 (2000) (citing Savage, supra, 134 N.J. at 243). In Martinez, the plaintiff's fiancee, Carl Farrish, was badly beaten in a street fight and died at the hospital shortly thereafter. The plaintiff knew of his injury and that it was the fault of another — the person who administered the beating. Indeed, Farrish's death certificate and accompanying publicity reflected that the death was a homicide. In addition, the physician at the hospital told the plaintiff "they did all they could." Id. at 49. Because the plaintiff was not present at the hospital, she did not know that, despite the fact that Farrish was in extremis, he waited for many hours before he received any medical treatment. On those facts, we held that the plaintiff "had no reason to suspect malpractice", id. at 57, until her lawyer was notified, in an anonymous letter, of what occurred at the hospital on the night of the beating. Thus, the complaint filed three and one-half years after Farrish's death, but within two years of the anonymous letter, was timely. In effect, Martinez reaffirmed that a cause of action may accrue against different defendants at different times.

Savage is another good example of that principle. In Savage, the plaintiff filed a medical malpractice action against physicians who had administered tetracycline to her in early childhood. The drug apparently discolored her teeth. The plaintiff became twenty-one in 1981. Until then the statute was tolled by reason of her age. She filed a complaint in 1989 alleging she was unaware until 1988 that her injury was due to the fault of her doctors. The trial judge ruled that because she had all the "facts" in 1981 at the time she reached majority, i.e. that her teeth were discolored and that medication given to her as a child might have caused the discoloration, she had only two years to bring suit. The Appellate Division disagreed. Savage v. Old-Bridge Sayreville Medical Group, P.A. 260 N.J. Super. 417 (1992). It reasoned that, although the plaintiff was aware that she had suffered injury and that the medication was a likely cause of it, the record did not reveal anything to suggest that she was or should have been aware that a lack of care in administering the medication was also a cause of her condition. Id. at 421-22.

We agreed with the Appellate Division's conclusion that, although plaintiff was aware of her injury and that the medicine was a likely cause of it, she was not aware that her injury was additionally due to her physicians' avoidable fault. Savage, supra, 134 N.J. at 247. In so ruling, we distinguished Savage's claims from those of the plaintiff in Apgar v. Lederle Labs. 123 N.J. 450, 453 (1992), whose untimely suit against the manufacturer we held time barred because the plaintiff knew, by the time she was eighteen years old, that the medicine she had taken as a child had discolored her teeth, that that medicine "had not been thoroughly tested", and that "certain things weren't right."

Two other cases that are instructive are Gallagher v. Burdette-Tomlin Mem'l Hosp. 163 N.J. 38 (2000), and Mancuso. In Gallagher, supra, 163 N.J. at 43-44, we held recently that a plaintiff could invoke the discovery rule long after she sued her surgeon for malpractice when she discovered that her after-care physicians were also at fault. That information was first made known to her during discovery in the case against the surgeon. Ibid. In Mancuso, supra, 163 N.J. at 36-37, we held that although the plaintiff pursued a malpractice cause of action against her surgeon, because she did not know or have reason to know that she also had a cause of action against her radiologist until she heard of his alleged malpractice during discovery in the original action, she could invoke the discovery rule to begin an action against him more than two years after his alleged malpractice.

Martinez, Savage, Gallagher and Mancuso reaffirm the basic principle that where 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. However, those cases also stand for the proposition that when a plaintiff knows of an injury, and knows that it is the fault of another, but is reasonably unaware that a third party may also be responsible, the accrual clock does not begin ticking against the third party until the plaintiff has evidence that reveals his or her possible complicity. Moreover, "notwithstanding that plaintiff discovers his cause of action for malpractice prior to the expiration of two years from the date of the actionable conduct, he nevertheless will ordinarily be allowed two full years from the date of such discovery to bring his action." Moran v. Napolitano, 71 N.J. 133, 134 (1976) (citing Fox v. Passaic Gen. Hosp., 71 N.J. 122, 126 (1976)).

III

Both the trial court and the Appellate Division ruled the complaint untimely by fifty-two days based on the notion that on August 4, 1993, Mrs. Caravaggio knew or should have known that she was injured and that Dr. D'Agostini bore some responsibility for that injury.

We disagree with that rather expansive view of what a reasonable person would or should have known on August 4, 1993. On that date, Mrs. Caravaggio was told by Dr. D'Agostini that there must have been something "structurally wrong" with the rod and that nothing the physical therapist did, at his behest, could have caused it to snap. It appears that those statements were made in good faith by Dr. D'Agostini who, even at the time of the Lopez hearing on May 22, 1998, and despite the metallurgic analysis, still believed that the Synthes Rod was defective. On August 4, 1993, Mrs. Caravaggio had no reason to assume either that he was being untruthful or that he had committed malpractice in the surgery. Indeed, that she did not believe so is underscored by the fact she later underwent further surgery at his hands, that her husband continued in his care, and that both of them referred family and friends to him. It was only when the rod was removed and found not to be defective that Mrs. Caravaggio might possibly have had reason to look elsewhere. The rod removal took place on October 21, 1993, and the complaint against Dr. D'Agostini was filed within two years of that date.

To be sure, Mrs. Caravaggio knew she was injured on August 4, 1993, and, in light of Dr. D'Agostini's statements, had reason to believe that the rod manufacturer was at fault as of that date. That is quite different from knowing or even suspecting Dr. D'Agostini's possible malpractice. Indeed, Mrs. Caravaggio was told, as part of the informed consent ritual at the time of the surgery, that even a procedure performed properly could result in the untoward complication of "rod breakage."

On August 4, 1993, when Mrs. Caravaggio knew the rod had broken, Dr. D'Agostini absolved the physical therapist and, inferentially, himself, indicating that the only thing he could think of was that there was something "structurally wrong" with the rod. Thus, on that date, Mrs. Caravaggio might reasonably have believed either that the rod breakage was just a "complication" of the surgery or that the manufacturer was responsible. She was entirely reasonable in not assuming that

Dr. D'Agostini or the therapist were to blame.

Until the rod was removed and analysis revealed that it was not defective, there was no reason for Mrs. Caravaggio to suspect some other cause. Even then, Dr. D'Agostini's negligence was not necessarily implicated. This is not a res ipsa case. Buckelew v. Grossbard, 87 N.J. 512, 525 (1981) (confirming use of res ipsa loquitur in medical malpractice cases, such that an inference of defendant's negligence is permitted "where (a) the occurrence itself ordinarily bespeaks negligence; (b) the instrumentality was within the defendant's exclusive control; and (c) there is no indication in the circumstances that the injury was the result of the plaintiff's own voluntary act or neglect." (quoting Bornstein v. Metropolitan Bottling Co., 26 N.J. 263, 269 (1958)). As we have noted, Dr. D'Agostini himself acknowledged that he advised Mrs. Caravaggio that rod breakage was a possible complication of properly performed surgery. It thus does not necessarily follow that a reasonable person would have concluded that one of the "universe" of defendants (manufacturer, therapist, physician) had to be responsible.

In Martinez, supra, in a different context, we said:

It is not necessary every time a person dies in a hospital for his or her relatives to immediately suspect malpractice. People die in hospitals in the absence of wrongdoing (for example, those gravely injured in accidents and the infirm elderly). Many times complications arise even if a procedure is performed perfectly. Medicine is not an exact science. Newmark v. Gimbels, 54 N.J. 585, 596-97 (1969). The rule accepted by the lower courts, that Ms. Martinez was unreasonable because she did not obtain and analyze Farrish's medical records even though she was not suspicious, encourages mistrust and essentially pits patients against their physicians even in cases where there is not even a trace of negligence apparent.

[ 163 N.J. at 58.]

That language is equally applicable here. Sometimes surgery results in complications, even if all procedures were performed correctly. People have heart attacks under anesthesia, develop blood clots, experience problems with wound healing, reject implants, and suffer failure of mobility after joint replacements. The possibilities, unfortunately, are legion. That is why surgery is always a last resort and why a patient is informed, prior to surgery, that a good result cannot be guaranteed even if the surgery is faultless.

Dr. D'Agostini did not cause Mrs. Caravaggio's original injury. He was retained to bring her back to health. That is what he was trying to do when he implanted the Synthes rod. When it broke and he told Mrs. Caravaggio that there must have been something structurally wrong with the rod, and assured her that the physical therapist could not have done anything to break a non-defective rod, there was no reason whatsoever for her to be suspicious of him. If the rulings of the trial court and the Appellate Division to the contrary were to be approved, it would have the untoward effect of pitting patients against their physicians, at a time at which they have no reason to doubt their physicians, in order not to risk losing their cause of action altogether.

It may be that after discovery and a trial on the merits, a jury will find that Dr. D'Agostini's performance of Mrs. Caravaggio's surgery was deficient. Our inquiry is solely focused on the period of time in 1993 when Mrs. Caravaggio learned the rod had broken. So focused, it is clear that her complaint was timely.

IV

Under presently existing standards governing the discovery rule, Mrs. Caravaggio acted in an objectively reasonable way in this matter, and the facts and circumstances, as known to her on August 4, 1993 did not warrant her concluding that Dr. D'Agostini was guilty of malpractice. She filed suit within two years of the removal of the rod. That was plainly within time.

V

The judgment of the Appellate Division is reversed. The matter is remanded to the Law Division for proceedings consistent with this opinion.