Nearly every adult plaintiff over thirty-five arrives with imaging that shows something. Disc bulges, facet arthropathy, a prior rotator cuff tear. The defense knows it, and the first move in most low-to-mid value spine and shoulder cases is the same: the crash did not cause this, age did. The better framing for plaintiff counsel is not to fight the degeneration but to make it irrelevant to the damages question.
The Legal Frame: Aggravation, Not Causation of the Condition
Most jurisdictions allow recovery when a tortfeasor aggravates a pre-existing condition or activates a dormant one. The plaintiff does not need to prove the crash created the underlying pathology. The claim is that the collision changed the plaintiff's trajectory: asymptomatic became symptomatic, conservative care became surgical, or a stable condition became a progressive one.
The standard jury instruction in many states, California's CACI 3927 and 3928 among them, separates two ideas. The first covers aggravation of a pre-existing condition or disability. The second covers the plaintiff who was unusually susceptible to injury, the so-called eggshell plaintiff, where the defendant is liable for the full extent of harm even if a healthier person would have fared better. Plead and argue both, because they answer different defense themes.
Build the Baseline Before the Defense Does
The strongest aggravation cases are won on the pre-crash record. Request at least five years of primary care, chiropractic, physical therapy, pharmacy, and employment records before you send a demand. You are looking for three things:
- Evidence the plaintiff was functioning: full-duty work, gym memberships, recreational activity, no recent specialist referrals.
- Gaps in treatment for the same body part, which show the condition was quiescent.
- Any prior claim, even a closed one, so you are not surprised at deposition.
Pharmacy records are underused. A plaintiff who filled no muscle relaxants or opioids for four years before the crash and then filled them within a week after it has a contemporaneous, third-party timeline that no one can attribute to litigation.
Imaging: Compare, Do Not Just Read
If a pre-crash MRI exists, obtain the actual images, not only the report, and give both studies to the same radiologist. Interval change is the most persuasive evidence in these cases: a new annular tear, a larger herniation, new edema or a new fracture line. Even where no prior imaging exists, a treating surgeon can often testify to acute findings versus chronic ones, such as Modic changes versus bone marrow edema, or osteophytes versus a fresh avulsion.
Do not oversell. If the radiology shows true degeneration with no acute change, the aggravation theory has to rest on clinical change and function, not on the film. Jurors discount an expert who insists everything on the MRI came from the collision.
Apportionment Is the Defense's Burden in Many States
Where a plaintiff proves aggravation, many jurisdictions place the burden on the defendant to apportion damages between the pre-existing condition and the crash. If the jury cannot separate them, the defendant bears the whole. That burden shift is worth confirming for your state and raising early in your pretrial brief and instruction requests, because it changes how the defense expert has to testify. A defense IME physician who says only that the plaintiff has degeneration has not carried an apportionment burden.
Press the defense expert on specifics at deposition. What percentage, based on what method? Would the plaintiff have needed this surgery in the same timeframe absent the crash? What is the literature on the natural history of asymptomatic disc disease progressing to surgery within months? Most defense experts cannot answer the last question with anything but generalities.
The Treating Physician Is the Linchpin
Retained experts matter, but a treating surgeon who explains why this plaintiff needed an operation after the crash and not before will outweigh them. Prepare the treater to explain the clinical reasoning in plain terms: mechanism of injury, onset of symptoms, failure of conservative care, and the decision to operate. Ask for a causation opinion stated to a reasonable degree of medical probability, and confirm the foundation includes the prior history. A causation opinion that ignores the plaintiff's prior records invites a motion to exclude.
For lien-based treatment, remember the bias cross. Treaters on lien will be asked about financial interest. Our coverage of lien and settlement practice addresses how providers can structure their testimony and billing to blunt that attack.
Damages Presentation
Frame damages around the delta. Show the jury a before-and-after: what the plaintiff did in the year before the crash and what they can do now. Future medical should be limited to what the aggravation requires, and your life care planner should state clearly which costs the plaintiff would have incurred anyway. Conceding that line up front is credible and takes away the defense's best cross.
Economic experts can value lost earning capacity the same way, comparing the pre-crash work-life expectancy to the post-crash one. For plaintiffs in physical occupations with documented prior back complaints, the vocational opinion should address why the crash, rather than gradual decline, ended the career.
Practical Checklist
- Collect five years of pre-crash records and pharmacy data before the demand.
- Obtain actual prior images and have one radiologist compare them.
- Request both aggravation and eggshell instructions.
- Confirm your state's apportionment burden and brief it early.
- Have treaters state causation with the prior history in the foundation.
- Concede the baseline in your own damages model.
For related work on the evidence side of crash cases, see our auto accident litigation coverage and the medical-expert sourcing pieces for guidance on retaining credible specialists.