Detailed Answer

Core legal principles

Under Missouri civil law, a defendant who causes or contributes to an injury is generally responsible for the full extent of the injury the plaintiff suffers, even if the plaintiff had a pre-existing weakness or condition. This principle—the so-called “eggshell plaintiff” idea—means a defendant cannot avoid liability simply because the injured person had a vulnerable back before the crash. You may recover damages for the aggravation of that pre-existing condition so long as you can prove the accident caused or materially contributed to the worsened condition.

What you must prove

• Causation: You must show the accident more likely than not caused or materially aggravated the back condition. Medical records and expert testimony (treating physicians, independent medical examiners) typically establish this link.
• Scope and extent: You must demonstrate how the condition changed after the accident (new symptoms, progression on imaging, need for additional treatment, loss of function).
• Damages: You must document economic losses (medical bills, future treatment costs, lost earnings) and non‑economic losses (pain and suffering, loss of enjoyment of life) attributable to the aggravation.
• Comparative fault: Missouri reduces a plaintiff’s recovery by that plaintiff’s share of fault if any. Evidence that you bore some responsibility for the accident can reduce your award.

How Missouri handles pre-existing conditions

Missouri courts will typically allow a plaintiff to recover for the aggravation of a pre-existing condition. If the accident made a dormant or mild back condition significantly worse, the defendant is responsible for the additional harm that resulted from the accident. The defendant is not required to pay for the condition in its entirety if some portion of the harm was unrelated to the accident; instead, the plaintiff must isolate and prove the damages caused by the accident.

Types of damages you can pursue

• Past and future medical expenses related to the aggravation (hospital bills, surgeries, physical therapy, medications, assistive devices).
• Past and future pain and suffering and emotional distress caused by the worsened condition.
• Lost wages and loss of earning capacity if your ability to work declined because of the exacerbated back problem.
• Cost of future care and home modifications, if the aggravation requires long‑term assistance.

Evidence the court or insurer will expect

• All medical records showing your pre‑accident condition and post‑accident care.
• Diagnostic imaging (MRIs, X‑rays) showing changes after the accident.
• Treating physicians’ notes and, if needed, expert medical testimony linking the accident to the aggravation.
• Records of lost earnings, job restrictions, and vocational evaluations if applicable.
• Documentation of daily limitations and testimony from you or others about changes in activities and quality of life.

Practical limits and defenses

Be prepared for common defenses: the defendant may argue the condition would have worsened regardless of the accident, that some treatments are unrelated, or that you failed to mitigate damages by not following recommended care. Missouri also applies comparative fault principles, which can reduce any award if you share fault for the accident. For more on Missouri civil damages and related rules, see the Missouri Revised Statutes, Chapter 537: Missouri Revised Statutes Chapter 537.

Time limits

Missouri imposes statutes of limitations for personal injury actions. You should act promptly because waiting can bar your claim. See Missouri Revised Statutes, Chapter 516 for limitations on civil actions: Missouri Revised Statutes Chapter 516. If you miss the deadline, the court will likely dismiss your case even if you have strong evidence.

How to demonstrate aggravation of a pre-existing back condition — step by step

1. Seek medically appropriate treatment right away. Immediate care creates a clear record tying your complaints to the accident.
2. Collect and preserve all prior medical records about your back condition so you (and medical experts) can compare before-and-after status.
3. Follow treating providers’ recommended care. Missing appointments or skipping treatment can be used against you.
4. Get clear documentation of new symptoms, new functional limits, and any increase in pain or treatment intensity after the accident.
5. Consider obtaining a medical expert opinion that explains how the accident aggravated your condition and estimates future medical needs.
6. Preserve evidence from the accident (photos, witness contact info, police reports) and document how the injury changed daily life and work.

When to consider hiring an attorney

Contact an attorney experienced in personal injury early if:

• Your injuries required emergency or ongoing medical care.
• You face substantial medical bills or long‑term care needs.
• Liability is disputed or the insurer offers a quick lowball settlement.
• There are complex questions about apportioning damages between pre‑existing harm and accident-related aggravation.

An attorney can help gather prior medical records, obtain expert testimony, calculate future damages, and negotiate with insurers or litigate in court if necessary.

Helpful Hints

• Get medical care immediately and keep all records — the timeline matters.
• Request and keep copies of your pre‑accident medical files; these show the baseline condition.
• Photograph injuries, accident scene, and any assistive devices you need after the accident.
• Track all accident-related expenses, travel for medical care, and missed work—accurate records strengthen your claim.
• Be cautious when speaking to the other party’s insurer; stick to facts and avoid detailed statements about pain or blame without legal guidance.
• If you see a new doctor for the post‑accident problem, ask the provider to explain in writing how the accident relates to the change in your condition.
• Start your claim promptly to avoid running into Missouri’s statute of limitations (see Chapter 516 linked above).