In a medical malpractice action, a claim is discovered when
the claimant knows the facts that form “the core of [the plain-
tiff’s] claim of substandard medical treatment”: Lawless v.
Anderson,  O.J. No. 519, 2011 ONCA 102, 81 C.C.L.T. (3d)
220, at para. 26. As M.G.J. Quigley J. observed in Thompson v.
Dr. Sehgal,  O.J. No. 2478, 2012 ONSC 3258 (S.C.J.),
at para. 42:
The material facts of which the plaintiff must be aware before the limitation
period can commence to run are those which would constitute negligence.
Negligence itself is composed not only of the breach of an applicable standard
of care, but also the causation to give rise to a cause of action.
 As I will explain, in my view, the motion judge erred in failing to identify the key difference between the appellants’ claims
against Dr. Barzo and their claims against the respondents. The
claim against Dr. Barzo is that he caused an injury during a chiropractic treatment. The core of the claim against all three
respondents, by contrast, is that, after this traumatic injury had
already occurred, and between June 28, 2011 and July 15, 2011
when Mr. Morrison had emergency surgery, they contributed to or
exacerbated Mr. Morrison’s injuries in their approach to treating
him and/or by failing to take more immediate action to respond to
the original traumatic injury. And if it turns out, as the appellants
assert, that the obligation to take certain immediate action only
arose if and when the respondents suspected CES, or in the case
of Ms. Edwards, a spinal nerve injury, then this affects the date of
 I turn to examine the specific allegations against each
respondent, and the evidence that was before the motion judge.
( i) The claim against Dr. Murphy
 Dr. Murphy’s involvement in Mr. Morrison’s care was at
the medical clinic where both Ms. Boulanger and Dr. Murphy
worked. The records of the clinic indicate that Ms. Boulanger
provided treatment to Mr. Morrison on June 28, 2011 and July 6,
2011. A note dated July 6, 2011 by Ms. Boulanger states that she
would consult Dr. Murphy regarding a prescription for narcotics
and x-rays. A lumbar spine x-ray was ordered the same day.
There is also a note on the same day from Ms. Boulanger saying
“To Emerg if pain gets unbearable”. On July 11, 2011, Dr. Mur-
phy saw Mr. Morrison and ordered an urgent CT scan. After
receipt of the CT scan, he advised Mr. Morrison to urgently
attend to see a neurosurgical specialist.
 On his examination for discovery, Dr. Murphy recounted
having spoken with Ms. Boulanger on July 6 about Mr. Morrison’s symptoms, which included a positive neurological sign, and