The Impact of Pre-Existing Conditions on Missouri Personal Injury Claims

If you’ve been injured in an accident and already had health issues, you might worry that your pre-existing condition will hurt your claim. The good news? Missouri law protects you. Your existing injuries or medical conditions don’t prevent you from getting compensation when someone else’s negligence makes them worse.

At SK Law, we’ve helped countless clients with pre-existing conditions secure fair compensation for their injuries. With over 100 years of combined legal experience, our attorneys understand exactly how Missouri law applies to these complex cases.

What Counts as a Pre-Existing Condition?

A pre-existing condition is any injury, illness, or medical problem that existed before your accident. Common examples include:

• Chronic back pain or disc problems
• Previous shoulder, knee, or hip injuries
• Arthritis or joint conditions
• Prior surgeries or fractures
• Diabetes or heart disease
• Old whiplash injuries
• Degenerative spine conditions.

According to the Centers for Disease Control and Prevention, three in four American adults suffer at least one chronic condition. This means millions of people carry some type of pre-existing condition into any accident they might experience.

Missouri’s Eggshell Plaintiff Rule: Your Legal Shield

Missouri recognizes something called the “eggshell plaintiff” rule. This legal principle says a negligent party must take their victim as they find them. Even if your pre-existing condition makes you more vulnerable to injury, the at-fault party is still responsible for all the harm they cause.

Think of it this way: if someone taps a fragile eggshell and it cracks, they’re responsible for the damage. They can’t argue that a normal skull wouldn’t have cracked.

The Missouri Supreme Court affirmed this principle in Miller v. Gulf Mobile & Ohio R.R. Co. The court held that defendants are liable for injuries caused or worsened by their actions, regardless of the victim’s pre-existing health status.

Example Scenario: How Pre-Existing Conditions Can Impact Claims

Consider this scenario: Sarah has chronic lower back pain from an old injury. She manages it with occasional physical therapy and over-the-counter medication. Then she’s rear-ended at a stoplight.

After the accident, Sarah’s back pain became severe. She needs epidural injections, extensive physical therapy, and eventually surgery. She can no longer work at her physically demanding job.

Under Missouri’s eggshell plaintiff rule, the at-fault driver is responsible for:

• The aggravation of Sarah’s back condition
• All new injuries from the accident
• The increased medical treatment she now requires
• Her lost wages and reduced earning capacity.

The insurance company will try to argue that Sarah’s surgery was inevitable due to her pre-existing condition. But if her lawyer and medical experts can show the accident accelerated her need for surgery or made her condition significantly worse, she can receive compensation for that harm.

Challenges Posed by Pre-Existing Conditions

While Missouri law protects your rights through the eggshell plaintiff rule, pre-existing conditions create real obstacles that you need to understand and prepare for.

Establishing Causation and Liability

The biggest challenge in these cases is proving that the defendant’s negligence caused your current injuries or made your condition worse. Defense attorneys will argue that your pain and limitations stem from your pre-existing condition, not the accident.

You need to establish that the defendant’s actions were a cause-in-fact of your injuries. Under Missouri law, this means showing that the accident was a substantial factor in bringing about your current condition, even if you wouldn’t have been as severely injured without your pre-existing vulnerability.

This challenge affects thousands of Missouri residents every year. The Missouri State Highway Patrol reported that 50,375 people were injured and nearly 1,000 killed in car accidents in 2023 alone. Many of these accident victims had pre-existing conditions when they got hurt.

Calculating Fair Damages

Determining compensation gets complicated when pre-existing conditions are involved. The jury or judge must separate:

• Injuries and expenses caused solely by the accident
• Aggravation of pre-existing conditions attributable to the defendant
• Pre-existing symptoms and limitations that would have existed regardless.

Medical testimony becomes critical here. Expert witnesses must clearly explain which portions of your current condition and treatment needs resulted from the accident versus your baseline health status.

According to the Centers for Disease Control and Prevention, unintentional injuries are the leading cause of death in the United States. When these injuries compound existing health problems, the impact on victims can be devastating.

The Evidence and Medical Records Battle

Pre-existing conditions require exhaustive medical documentation. You need to establish:

• Your baseline health before the accident
• The specific aggravation caused by the defendant’s conduct
• How your daily life has changed since the incident
• Your future medical needs and prognosis.

This means gathering years of medical records, comparing diagnostic tests from before and after the accident, and presenting expert opinions that withstand cross-examination.

Jury Perception and Skepticism

Juries can be skeptical when plaintiffs have significant pre-existing conditions. Defense counsel will emphasize your prior health problems, suggesting that:

• Your current suffering was inevitable
• The accident just revealed problems that were already there
• You’re exaggerating how much worse you feel now, or
• Your injuries would have required treatment anyway.

Overcoming this skepticism requires compelling evidence and an effective presentation of your case. This is where experienced legal representation makes the difference.

Missouri Statutory and Procedural Considerations

Missouri law provides a specific framework for handling personal injury claims involving pre-existing conditions. Understanding these legal principles is essential to protecting your rights.

Comparative Fault and Pre-Existing Conditions

Missouri follows a pure comparative fault system under Revised Statutes of Missouri (RSMo) section 537.765. This statute states that if the plaintiff (claimant) contributed to their own injury, they’re not completely barred from compensation. Instead, any fault attributable to the plaintiff reduces their compensation proportionately.

Here’s how this applies to pre-existing conditions: If your pre-existing condition resulted from your own prior negligence (for example, you never treated an old injury properly), defense attorneys might argue this increases your comparative fault percentage.

However, simply having a pre-existing condition doesn’t make you comparatively at fault. The key question is whether your actions at the time of the current accident contributed to your injuries.

Missouri Pattern Jury Instructions

Missouri courts use Missouri Approved Instructions (MAI) to guide juries on damages and pre-existing conditions. These instructions emphasize to juries that defendants are liable for injuries they cause or worsen, consistent with the eggshell skull rule.

The instructions tell jurors they must compensate plaintiffs for all harm caused by the defendant’s negligence, even when pre-existing vulnerabilities make the injuries more severe than expected.

Joint and Several Liability Considerations

Under RSMo section 537.067, Missouri has modified joint and several liability rules. If a defendant is found to bear 51% or more of fault, they’re jointly and severally liable for the full judgment. If they bear less than 51% fault, they’re only responsible for their proportionate share.

This matters in cases involving multiple defendants where pre-existing conditions complicate fault allocation.

The Role of Expert Medical Testimony

Missouri courts rely heavily on expert testimony to delineate pre-existing conditions from accident-related injuries. Expert witnesses may include:

• Treating physicians who can describe changes in your condition
• Independent medical examiners who review your complete medical history
• Vocational rehabilitation specialists who evaluate your ability to work
• Life care planners who project future medical needs.

These experts must meet Missouri’s standards for admissibility under the Daubert standard, meaning their testimony must be based on reliable methods and scientific principles.

Missouri Statute of Limitations

Missouri Revised Statutes section 516.120 gives you five years from the accident date to file a personal injury lawsuit. This is longer than many states, but waiting still hurts your case because:

• Medical records become harder to obtain
• Witnesses’ memories fade
• Physical evidence may be lost
• Your credibility suffers if you delay seeking legal help.

Defense Strategies in Missouri

Understanding how defense attorneys approach pre-existing condition cases helps you prepare for the arguments you’ll face.

Minimizing Causation

Defense lawyers will aggressively argue that your injuries stem primarily from your pre-existing condition, not the accident. They’ll point to:

• Your medical history shows similar symptoms before the accident
• The “minor” nature of the collision or incident
• Time gaps between the accident and when you sought treatment
• Activities you continued doing after the accident.

Their goal is to convince the jury that the defendant’s actions were, at most, a minor contributing factor to your current condition.

Challenging the Extent of Damages

Even if they can’t deny causation entirely, defense attorneys will try to minimize how much worse the accident made your condition. They’ll use their own medical experts to argue:

• Your condition would have deteriorated naturally regardless of the accident
• The treatment you received was unnecessary or excessive
• Your symptoms are subjective and can’t be verified objectively
• You’re not as limited in your daily activities as you claim.

Questioning Your Credibility

Defense teams will scrutinize your entire life, looking for inconsistencies. They’ll use:

• Social media posts showing you engaged in physical activities
• Surveillance footage of your daily routine
• Inconsistent statements you made to different doctors
• Gaps or irregularities in your treatment history.

They want to paint you as someone exaggerating their injuries or trying to profit from a pre-existing condition.

Arguing Comparative Fault

Defense attorneys will look for any way to shift the blame to you. With pre-existing conditions, they might argue:

• You failed to properly treat your pre-existing condition, making yourself more vulnerable
• You engaged in activities that worsened your condition after the accident
• You didn’t follow medical advice, contributing to your current state
• Your lifestyle choices (weight, smoking, lack of exercise, or the like) made your injuries worse.

Under Missouri’s comparative fault system, even small percentages of fault attributed to you reduce your compensation.

Emphasizing Pre-Accident Medical Bills

Defense lawyers will highlight every dollar you spent on medical care before the accident. They want to show that:

• You were already spending significant money on healthcare
• Your current medical bills aren’t much different from before
• The accident didn’t really change your financial situation
• Your “damages” are just a continuation of pre-existing costs.

Using Independent Medical Examinations

The defense will likely require you to undergo an independent medical examination (IME) with a doctor of their choosing. These doctors often provide opinions favorable to insurance companies, downplaying the accident’s impact on your pre-existing condition.

Expect the IME doctor to spend minimal time examining you while spending hours reviewing your medical history, looking for ammunition to use against your claim.

What Insurance Companies Do to Minimize Your Claim

Insurance adjusters use predictable tactics when pre-existing conditions are involved:

They Downplay the Accident’s Impact

Adjusters will argue that a minor accident couldn’t have significantly worsened your condition. They’ll point to low property damage or slow-speed collisions as “proof” that you couldn’t have been seriously hurt.

But as experienced personal injury attorneys know, low-impact crashes can absolutely aggravate pre-existing conditions. The eggshell plaintiff rule protects you in exactly these situations.

They Suggest Your Symptoms Are Unrelated

Insurance companies love to claim your current pain is just a continuation of old problems. They’ll hire their own doctors to review your records and provide opinions favorable to their position.

This is why having your own medical experts is so important. The battle often comes down to competing medical opinions, and you need strong advocates on your side.

They Offer Quick, Low Settlements

Adjusters know that medical bills pile up fast, especially when you have ongoing health issues. They’ll offer quick settlements, hoping you’ll accept less than your claim is worth.

Don’t rush into a settlement without understanding the full extent of your injuries and future needs. Once you accept, you typically can’t ask for more money later.

What to Do: Strategies for Claimants with Pre-Existing Conditions

If you have pre-existing conditions and have been injured in an accident, these strategies strengthen your claim and counter defense tactics:

Maintain Comprehensive Medical Documentation

Your medical records are your most powerful evidence. You need:

Complete Pre-Accident Records

Gather all medical documentation from before the accident showing:

• Your baseline condition and symptoms
• Treatment frequency and intensity
• Functional abilities and limitations
• Medication regimens
• Diagnostic test results.

Detailed Post-Accident Records

Document every aspect of your care after the accident:

• Emergency room visits and initial evaluations
• Follow-up appointments with all providers
• Physical therapy and rehabilitation sessions
• Diagnostic imaging showing changes or new injuries
• Changes in medication or treatment plans.

The contrast between before and after establishes how the accident affected you.

Secure Strong Expert Medical Testimony

Credible medical experts are essential. They can:

• Explain the specific mechanism by which the accident worsened your condition
• Distinguish between pre-existing symptoms and new or aggravated problems
• Describe how the trauma accelerated degenerative processes
• Project your future medical needs and costs
• Counter defense medical opinions with solid scientific reasoning.

Choose experts with strong credentials who communicate clearly and withstand aggressive cross-examination.

Build a Clear Causation Argument

Focus your case on demonstrating that the defendant’s actions were a substantial factor in causing new injuries or aggravating existing conditions. Show:

• You had a pre-existing condition, but managed it successfully
• The accident caused immediate changes in your symptoms or function
• Medical evidence directly links the trauma to your worsened condition, AND
• Your treating physicians agree that the accident caused the aggravation.

Don’t shy away from your pre-existing condition. Acknowledge it openly while clearly showing how the accident made everything worse.

Calculate Damages Precisely

Separate your damages into clear categories:

Pre-Accident Baseline

Document your medical expenses, work capabilities, and quality of life before the accident.

Accident-Related Changes

Calculate the additional costs and losses attributable solely to the accident:

• Increased medical expenses
• New medications or treatments
• Lost wages beyond any pre-existing work limitations
• Additional pain and suffering
• New activity restrictions.

Future Damages

Project ongoing costs resulting from the accident’s impact on your pre-existing condition.

Document Functional Changes

Numbers and medical records tell part of the story. Personal testimony tells the rest. Gather evidence showing:

• Activities you could do before, but can’t do now
• How your work performance has changed
• The impact on your relationships and family life
• Hobbies or recreational activities you’ve had to give up
• Daily tasks that have become difficult or impossible.

Ask family members, friends, and coworkers to provide statements describing changes they’ve observed in you since the accident.

Be Completely Honest About Your Medical History

Never hide or minimize your pre-existing conditions. Insurance companies will discover them through:

• Medical record authorizations you sign
• Insurance claim databases
• Social media research
• Investigator surveillance.

Attempting to conceal pre-existing conditions destroys your credibility and can result in your entire claim being denied. Instead:

• Disclose all pre-existing conditions upfront
• Explain how well you managed them before the accident
• Demonstrate how drastically things changed after the accident
• Let your attorney frame your pre-existing conditions in the proper legal context.

Follow All Medical Advice

Comply strictly with your treatment plan. Defense attorneys love to argue that plaintiffs who skip appointments or ignore medical advice caused their own continued suffering.

Document your compliance through:

• Attendance at all scheduled appointments
• Following prescribed therapy regimens
• Taking medications as directed
• Making recommended lifestyle modifications.

Avoid Social Media Pitfalls

Insurance companies monitor claimants’ social media accounts looking for contradictory evidence. Don’t post:

• Photos or videos of physical activities
• Check-ins at gyms, amusement parks, or sporting events
• Comments minimizing your injuries or symptoms
• Anything that could be misinterpreted as inconsistent with your claimed limitations.

Better yet, stay off social media entirely while your claim is pending.

Work With Experienced Legal Representation

Pre-existing condition cases are too complex to handle alone. An experienced Missouri personal injury attorney will:

• Obtain and organize all relevant medical records
• Retain qualified medical experts
• Develop compelling evidence of causation
• Counter defense tactics effectively
• Negotiate from a position of strength
• Take your case to trial if necessary.

Types of Compensation Available in Missouri Personal Injury Cases

When your pre-existing condition has been worsened by someone’s negligence, you may be entitled to:

Economic Damages

• Medical expenses (past and future)
• Lost wages and earning capacity
• Rehabilitation and therapy costs
• Prescription medications
• Assistive devices or home modifications
• Transportation to medical appointments.

Non-Economic Damages

• Pain and suffering
• Emotional distress
• Loss of enjoyment of life
• Reduced quality of life
• Loss of consortium (for your spouse).

The key is proving which expenses and losses stem from the accident’s aggravation of your condition versus your baseline pre-existing issues.

Why Experience Matters in Pre-Existing Condition Cases

These claims require sophisticated legal and medical knowledge. At SK Law, we bring that expertise to every case.

Our firm has been serving Missouri clients since 1984, and our attorneys have earned the highest ratings in the legal profession. These include the AV Preeminent Peer Review Rating by Martindale-Hubbell, which represents the highest recognition for professionalism and ethics. We’ve also received Super Lawyers ratings, awarded to less than 5% of attorneys.

We know how to:

• Counter insurance company tactics
• Work with medical experts who can convincingly explain your injuries
• Negotiate effectively or take your case to trial when necessary
• Protect your rights under Missouri law.

Choose SK Law: Why Missouri Claimants Us

When you work with our firm, you get:

• Over a century of combined legal experience: Our attorneys have successfully handled thousands of personal injury cases across Missouri. We know how courts and insurance companies approach pre-existing condition cases.
• Proven track record: We’ve secured favorable outcomes for clients throughout St. Charles, Lincoln, St. Louis, and Warren counties. Our reputation speaks for itself through our AV Preeminent ratings and client testimonials.
• Comprehensive case preparation: We work with top medical experts, accident reconstruction specialists, and vocational rehabilitation professionals to build the strongest possible case.
• Personalized attention: We provide clear updates at every step, so you always know where your case stands and what to expect next.
• No upfront costs: We handle personal injury cases on a contingency fee basis. You don’t pay unless we recover compensation for you.

Get the Experienced Legal Help You Deserve for Your Pre-Existing Conditions and Missouri Personal Injury Claims

Don’t let insurance companies tell you that your pre-existing condition means you can’t recover compensation. Missouri law explicitly protects your rights through the eggshell plaintiff rule.

Yes, these cases are more complicated. Yes, insurance companies will fight harder. But with experienced legal representation, you can hold negligent parties accountable and secure the compensation you deserve.

The accident wasn’t your fault. Neither was your pre-existing condition. You shouldn’t have to suffer because someone else’s negligence made your health problems worse.

If you’ve been injured in an accident and have pre-existing conditions, don’t wait. Contact SK Law today for a free consultation. We’ll review your case, explain your rights under Missouri law, and fight to get you every dollar you deserve.

With our 100+ years of combined legal experience and proven track record of success, we have the knowledge and skills to handle even the most complex pre-existing condition cases. We’ve helped countless Missouri residents secure fair compensation after accidents worsened their existing health problems.

Our top-rated attorneys serve clients throughout St. Charles, Troy, Lincoln, and the surrounding areas in Warren and St. Louis counties. We also represent clients from Illinois.

Call (636) 946-9999 now or contact us online to schedule your free, no-obligation consultation. Let us put our expertise to work for you.

Remember: The sooner you act, the stronger your case will be. Don’t let insurance companies take advantage of you. Get experienced legal help today.