concurring in part and dissenting in part:
I agree with the majority, for the reasons stated in Judge Lynn’s careful opinion, that the trial court was correct to grant partial summary judgment on Hamburger’s extra-contractual claims, exclude Dr. Fitzgerald’s expert testimony on causation, grant judgment as a matter of law on Hamburger’s claim for medical expenses related to the herniated disc, and offset the jury verdict with funds already paid to Hamburger. Because I believe that lay testimony was insufficient under Texas law to establish causation in this case, I would also affirm the trial court’s entry of judgment as a matter of law on the issue of the cause of Hamburger’s herniated disc. The majority sets out the proper governing principles concerning whether lay testimony was required, but I would simply reach a different conclusion on this record. For that reason, I respectfully dissent from that portion of the majority’s opinion and judgment.
As the majority correctly explains, the leading Texas authority on this question is Morgan v. Compugraphic Corp., 675 S.W.2d 729 (Tex.1984). There, the Texas Supreme Court stated the following rule regarding when expert testimony on causation is required:
Lay testimony is adequate to prove causation in those cases in which general experience and common sense will enable a layman to determine, with reasonable probability, the causal relationship .between the event and the condition. Generally, lay testimony establishing a sequence of events which provides a strong, logically traceable connection between the event and the condition is sufficient proof of causation.
Id. at 733 (citation omitted).1
The application of this rule is necessarily case-specific. There will be some cases in which the causal connection between an event and an injury is so plain that no fair-minded observer could reject it, but in other cases the causal connection is so attenuated that the layperson can only engage in rank speculation as to whether any connection exists. Some Texas cases suggest that certain types of injuries may be, as a categorical matter, beyond the ken of the layperson. See, e.g., Burroughs Wellcome Co. v. Crye, 907 S.W.2d 497, 499 (Tex.1995) (“The nature of a frostbite injury is such that expert medical testimony is required to establish causation.”). In most cases, however, the decision turns not only on the type of injury but also on the surrounding circumstances. Thus, some cases involving herniated discs will not require expert testimony on causation, see, e.g., Fid. & Guar. Ins. Underwriters, Inc. v. La Rochelle, 587 S.W.2d 493, 494, 496-97 (Tex.Civ.App.—Dallas 1979, writ refd n.r.e.) (protruding disc in plaintiffs back), but other cases involving similar injuries will require an expert opinion, depending on whether (according to the facts of the case) “general experience and common sense will enable a layman to determine, with reasonable probability, the causal relationship between the event and the condition.” Morgan, 675 S.W.2d at 733.
I find some of the details in the record before us quite relevant to the question *889whether “general experience and common sense” will suffice in this case. Hamburger testified, and his wife agreed, that he never had any problems with his neck before the July 26 accident. Immediately after the accident, he experienced “general stiffness and some pain” in his neck, but he did not seek any medical treatment at that time. The pain continued and grew quantitatively worse over the next several weeks, but at some point between four and eight weeks after the accident the pain also changed qualitatively: “[A]ll of a sudden one day,” Hamburger testified, “the pain just progressed from my neck and— to the shoulder and down my arm.” It was this new species of pain that led him to the doctor in early November. It was later determined that his nerves were being compressed by a herniated disc.
The tests performed on Hamburger revealed not only the herniated disc but also some degenerative changes in his neck and spine. Although there was no testimony on whether Hamburger’s accident caused his herniated disc (the operating surgeon would have opined that there was a connection, if the court had permitted it), there was expert testimony on the types of things that can cause a herniated disc. According to the testimony, it could be associated with degenerative conditions or with trauma. The category of trauma includes car accidents, but, according to the expert testimony, it also includes exercising and even sneezing — anything that “[clauses the body to jerk in any direction suddenly.” The record in this case thus discloses both a delayed onset and possible competing causes, features that tend to erode the common sense causal connection between Hamburger’s accident and his herniated disc. See, e.g., III. Employers Ins. of Wausau v. Wilson, 620 S.W.2d 169, 172 (Tex.Civ.App.—Tyler 1981, writ ref'd n.r.e.) (holding that the length of time between the plaintiffs shin laceration and the subsequent gangrene and amputation, together with the complexity of the injury, required expert testimony on causation); Orkin Exterminating Co. v. Davis, 620 S.W.2d 734, 736-37 (Tex.Civ.App.—Dallas 1981, writ refd n.r.e.) (requiring expert testimony where the plaintiffs nerve injuries to his neck and back might have been caused by an improper neck brace or congenital abnormalities).
To be sure, the factors just listed are in no way determinative. There are cases from the Texas appellate courts that do not require expert testimony even when these types of confounding factors are apparently present. In particular, the case of Blankenship v. Mirick, 984 S.W.2d 771 (Tex.App.—Waco 1999, pet. denied), cited by the majority, is in many ways quite similar to today’s case. The plaintiff in that case received medical treatment immediately after her ear accident for lacerations and abrasions to her knees, but x-rays were initially normal. Id. at 773. Only many months later did x-rays reveal laterally shifted kneecaps that eventually required surgery. Id. at 773-74. There was a suggestion in that case, based on testimony from the treating physician, that some people have a congenital susceptibility to patellar dislocations. Id. at 776. The physician was unable to say with any degree of confidence whether the plaintiffs dislocated kneecaps were caused by the accident or by a previously undetected preexisting condition. Id.
Blankenship is a persuasive guidepost, but I believe that it is subtly different from today’s case in ways that bear on the need for expert testimony. First, while the physician in Blankenship testified that a preexisting condition could cause knee problems of the sort the plaintiff suffered, he did not testify that the plaintiff actually had any such condition. Here, in contrast, Hamburger actually did have signs of degenerative changes, though admittedly *890they were deemed “not dramatic.” The Texas courts frequently require expert testimony when there are competing causes. See Lenger v. Physician’s Gen. Hosp., Inc., 455 S.W.2d 703, 707-08 (Tex.1970); Coastal Tankships, U.S.A., Inc. v. Anderson, 87 S.W.3d 591, 603-04 (Tex.App.—Houston [1st Dist.] 2002, pet. denied). Nonetheless, even in the presence of competing causes, lay jurors are still permitted to reach their own conclusions as to causation in cases where there is a close relationship between an accident and an injury' — when, in Morgan’s, language, there is “a sequence of events which provides a strong, logically traceable connection between the event and the condition.” 675 S.W.2d at 733. If Hamburger had experienced pain in his extremities and been diagnosed with a herniated disc shortly after the accident, I think that a juror’s common sense could properly attribute the injury to the accident rather than to background causes. But the connection between the accident and the injury is more attenuated on this record, since Hamburger’s symptoms changed after one to two months from “general stiffness and some pain” to severe pain shooting down to his arm.
A second relevant difference is that while there was a delayed onset in Blankenship, in that case there was also expert medical testimony that explained how the delayed reaction could occur: The surgeon testified that pain from the accident could have led the plaintiff to avoid exercising the muscles around the knee, letting the muscles gradually atrophy to the point that the kneecap could slide out of its normal position. 984 S.W.2d at 776. In today’s case, the jury did not hear a causal story that would explain the discontinuous progress of Hamburger’s symptoms. I do not believe that the question of whether a car wreck could cause a herniated disc that does not manifest itself until weeks later is within “general experience and common sense” such that a layperson can “determine, with reasonable probability, the causal relationship between the event and the condition.” Morgan, 675 S.W.2d at 733. I would hold that expert testimony is therefore necessary. That requirement can often be satisfied with a single question posed to a physician who is already testifying as a fact witness — as would have happened here, if Hamburger’s surgeon had been properly designated under Federal Rule of Civil Procedure 26(a)(2)(A).
Since my application of the governing Texas principles would require expert testimony on this record, I respectfully dissent to the extent that the majority holds otherwise. I concur -in the balance of the majority’s judgment and opinion.
. I treat the question whether an expert is needed in this diversity case as a question governed by state law. I recognize that the distinction drawn in our cases between the amount of evidence required, which is a function of federal law under Federal Rule of Civil Procedure 50, and the kind of evidence required, for which we look to state law, becomes rather slippery in this context. Nonetheless, I agree with the majority that our cases treat this question as a matter of state law. From the point of view of the Erie interest in avoiding forum shopping, it is sensible to follow the state rules regarding when expert testimony is needed to prove causation.