Today we consider why section 5(1)(a)(iv) of the Limitations Act features so infrequently in limitations analyses, and by extension, a trend in the jurisprudence toward analyses based on the common law principle of discoverability rather than the Limitations Act.
Section 5(1) of the Limitations Act provides the requirements for subjective discovery of a claim:
(1) A claim is discovered on the earlier of,
(a) the day on which the person with the claim first knew,
(i) that the injury, loss or damage had occurred,
(ii) that the injury, loss or damage was caused by or contributed to by an act or omission,
(iii) that the act or omission was that of the person against whom the claim is made, and
(iv) that, having regard to the nature of the injury, loss or damage, a proceeding would be an appropriate means to seek to remedy it […]
Subject to a few notable exceptions, you rarely see a limitations analysis that turns on the fourth requirement, the appropriateness of a proceeding as a remedy.
My working theory is that, at least in recent years, this is largely the result of the Court of Appeal decision in Lawless v. Anderson (2011). Lawless has two much-cited paragraphs describing discoverability:
 The principle of discoverability provides that “a cause of action arises for the purposes of a limitation period when the material facts on which it is based have been discovered, or ought to have been discovered, by the plaintiff by the exercise of reasonable diligence. This principle conforms with the generally accepted definition of the term ‘cause of action’ – the fact or facts which give a person a right to judicial redress or relief against another”: Aguonie v. Galion Solid Waste Material Inc. (1998), 1998 CanLII 954 (ON CA), 38 O.R. (3d) 161 (C.A.), at p. 170.
 Determining whether a person has discovered a claim is a fact-based analysis. The question to be posed is whether the prospective plaintiff knows enough facts on which to base an allegation of negligence against the defendant. If the plaintiff does, then the claim has been “discovered”, and the limitation begins to run: see Soper v. Southcott (1998), 1998 CanLII 5359 (ON CA), 39 O.R. (3d) 737 (C.A.) and McSween v. Louis (2000), 2000 CanLII 5744 (ON CA), 132 O.A.C. 304 (C.A.).
What’s noteworthy about this description, and to my knowledge never mentioned in the decisions that rely on it, is that this is the common law principle of discoverability. This is why the authorities cited by the Court in support of the principle all predate the current Limitations Act.
The legislature codified the common law principle of discoverability into section 5 of the Limitations Act, but not without materially altering it. Section 5 doesn’t use the language of “cause of action” (nor does the Limitation Act generally), and, above all, by operation of 5(1)(a)(iv) it makes the appropriateness of the proceeding a condition of discovery.
You can square sections 5(1)(a)(i) – (iii) with the common law principle of discoverability. These provisions require the claimant to know facts that comprise, more or less, the elements of most causes of action (that is, for any cause of action to accrue there needs to be injury caused by someone to the plaintiff). However, it’s a lot more difficult to square section 5(1)(a)(iv) with the common law principle. I can’t think of any cause of action that has as an element the appropriateness of a legal proceeding.
If you use the principle of discoverability in Lawless as the starting point of a discovery analysis, you either need to adopt an expansive and awkward limitations-specific definition of cause of action, which I don’t see happening, or you discount (if not ignore entirely) section 5(1)(a)(iv). And so we see so many limitations decisions since Lawless that don’t consider whether the appropriateness of a proceeding affects the commencement of the limitation period.
There are other reasons for this, too, I suspect. The jurisprudence offers rather little guidance on the meaning of “appropriate”. The leading decision, as you’ll see below, defines it vaguely as “legal appropriateness”.
In any event, this is all to say that it’s refreshing to encounter Brown v. Baum, a medical malpractice decision in which Justice Mew concludes that section 5(1)(a)(iv) operated to delay the commencement of the limitation period. This is the decision you should look to when considering a section 5(1)(a)(iv) response to a limitations defence.
Dr. Baum performed plastic surgery on Brown. It did not have the desired effect. Brown sued Baum, who moved for summary judgment on the basis of a limitations defence. The relevant paragraphs follow:
 The defendant argues that by no later than July 2009, Ms. Brown had independently formed the view that Dr. Baum had done something wrong. Even if it accepted that Ms. Brown was not informed of all of the risks associated with the procedures she underwent, she knew that things had not gone well. She did not need a second opinion or legal advice to reach that conclusion.
 I agree with the defendant. That does not, however, end the analysis.
 There are four limbs to s. 5(1)(a) of The Limitation Act, 2002. All four must be satisfied before time will start to run against a plaintiff.
 It is clear from the record that while Ms. Brown, by no later than July 2009, knew that (a) an injury loss or damage had occurred; (b) that the injury loss or damage had been caused or contributed to by an act or omission; and (c) that the act or omission was that of Dr. Baum; the fourth limb must also be established, namely, “that, having regard to the nature of the injury, loss or damage, a proceeding would be an appropriate means to seek to remedy it”.
 Following the initial surgery in March 2009, Ms. Brown returned to Dr. Baum on a number of occasions, including several surgeries, during the course of which Dr. Baum attempted to improve the outcome of the initial surgery.
 Although this action was started well in excess of two years after both the March 2009 surgery and July 2009 (by which time Ms. Brown had formed the view that Dr. Baum had done something wrong), it was commenced within two years of the last in the series of surgical procedures undertaken by Dr. Baum, which was on 16 June 2010.
 In Markel Insurance Company of Canada v. ING Insurance Company of Canada, 2012 ONCA 218 (CanLII) at para. 34, the Court of Appeal considered the meaning of the term “appropriate” in the context of s. 5(1)(a)(iv). According to Sharpe J.A.:
…I fully accept that parties should be discouraged from rushing to litigation or arbitration and encouraged to discuss and negotiate claims. In my view, when s. 5(1)(a)(iv) states that a claim is “discovered” only when “having regard to the nature of the injury, loss or damage, a proceeding would be an appropriate means to seek to remedy it”, the word “appropriate” must mean legally appropriate. To give “appropriate” an evaluative gloss, allowing a party to delay the commencement of proceedings for some tactical or other reason beyond two years from the date the claim is fully ripened…would, in my opinion, inject an unacceptable element of uncertainty into the law of limitation of actions.
 Where, as in the present case, the defendant has conducted a series of surgical procedures on the plaintiff over 15 months with the goal of producing an optimal outcome, the limitation issue which arises is whether it would have been “appropriate” for the plaintiff to commence a proceeding against the defendant before the last in the series of surgeries performed by him.
 Dr. Baum performed a series of surgeries on Ms. Brown over a period of 15 months. The defendant argues that, assuming that time would run from either March 2009 (the date of the first surgery) or July 2009 (the time by which the first three limbs of s. 5(1)(a)(iv) had been satisfied), even if Ms. Brown had wanted to refrain from commencing an action until she stopped seeing Dr. Baum, there would have been time for her to have done so following the final consultation visit in June 2010.
 This argument misses the point of subparagraph (iv), which is to delay the commencement of the limitation period until such time as initiating a proceeding is an appropriate remedy. The point can be illustrated by assuming that, instead of the series of surgeries having been conducted over 15 months, the time span between the first surgery and the last surgery was, say, 36 months. If one assumes that the date of the first surgery is the date on which the limitation period runs (which, presumptively, it would be: Limitations Act, s. 5(2)), then the plaintiff would be required to commence an action against the defendant while still receiving treatment from him. The service of a statement of claim on a treating physician by a patient would almost certainly result in a termination of the doctor-patient relationship and, hence, efforts to ameliorate – or remedy – the patient’s condition through continued treatment of the plaintiff patient by the physician.
 When considering the recommendation of legislation identical to s. 5(1)(a)(iv) in British Columbia, the British Columbia Ministry of Justice observed (The New Limitation ActExplained (Victoria, Civil Policy and Legislation Office, Ministry of Justice: 2013) (online www.ag.gov.bc.ca/legislation/limitation-act/pdf/LA_Explained.pdf at 26) that the provision:
…recognizes that courts will continue to have considerable discretion in interpreting the meaning of the discovery test, in order to come to a just result, and to achieve fairness for plaintiffs.
 Each case will, of course, turn on its particular facts. It will not be every case in which the fact that a physician-patient relationship is ongoing that it would be appropriate to toll the running of the limitation period until that relationship has terminated. Nor in every case where there is a series of surgical procedures undertaken will time not run until the last of those procedures has been undertaken. It will depend on the facts and circumstances.
 In the present case the defendant continued for over a year after the initial surgery to achieve a better outcome for the plaintiff. There was no doubt about what he was doing or why he was doing it. There is no indication in the evidence that the defendant was motivated by a concern to minimise his potential liability to the plaintiff. It would be unreasonable and inappropriate in such circumstances to start the two year limitation clock running against Ms. Brown while the defendant’s good faith efforts to achieve a medical remedy continued.
 In my view, the effect of s. 5(1)(a)(iv) in the present case is to delay the commencement of the two year limitation period until no earlier than the date of the last surgery on 16 June 2010. As the plaintiff’s action was commenced within two years of that date, the action is not statute barred. There is no triable issue based on the limitation defence. The defendant’s motion for summary judgment is therefore dismissed.
Note that applying the common law principle of discoverablity from Lawless to these facts (instead of the Limitations Act) would almost certainly have resulted in the limitations defence succeeding.