If you have ever been told by an insurance adjuster that your work injury “is not really work-related” because you had a pre-existing condition, you are not alone. Denials based on degenerative changes, prior injuries, or asymptomatic conditions found on imaging are one of the most common reasons Illinois injured workers are forced to fight for the benefits they deserve. A recent decision from the Illinois Appellate Court, Workers’ Compensation Commission Division, narrows the space for one version of that defense.
In Tazewell County v. Illinois Workers’ Compensation Comm’n, 2025 IL App (4th) 230754WC, the court resolved a question of first impression in Illinois: whether work-related repetitive activity that produces pain from an underlying pre-existing condition — without causing any new structural damage — can be compensable under the Illinois Workers’ Compensation Act. The court’s answer is yes, when the evidence supports a causal link. For injured workers throughout DuPage, Cook, Will, Kane, and Lake counties, this is an important clarification of a legal issue that has long been used by employers and insurance carriers to defeat valid claims.
The Facts of the Case
The petitioner was a dental hygienist whose daily work involved repetitive pushing, pulling, reaching, and holding tools at or above shoulder level. Over time, she developed worsening pain in her left shoulder. Imaging and orthopedic evaluation revealed rotator cuff pathology, acromioclavicular joint arthrosis, bursitis, and biceps tenosynovitis. Conservative treatment failed, and her surgeon recommended surgery.
There was no dispute that some of the underlying pathology pre-dated the alleged repetitive trauma. Both the treating surgeon and the employer’s Section 12 examiner agreed that the rotator cuff tear itself was not caused by her work. The disagreement focused on whether her job duties caused the painful symptoms that finally drove her to seek treatment.
The treating surgeon opined that the petitioner’s repetitive work activities at and above shoulder level were a “contributory cause of pain at her left shoulder” and that repetitive overhead reaching can produce increased pain in patients with underlying rotator cuff pathology. The employer’s examiner conceded that work activity could trigger shoulder pain in someone with a rotator cuff tear, but characterized any such pain as a “very temporary aggravation or manifestation of symptoms” rather than a permanent worsening of the underlying condition.
The arbitrator initially denied the claim, finding insufficient evidence of accident or causation. The Illinois Workers’ Compensation Commission reversed the arbitrator and awarded benefits, crediting the treating surgeon’s causation opinion. The circuit court of Tazewell County confirmed the Commission, and the employer appealed.
The Court’s Holding
The appellate court affirmed the Commission and squarely addressed the legal question that has divided arbitrators and defense lawyers for years: whether the aggravation of a pre-existing condition can be compensable under Illinois law when the work activity causes painful symptoms but no new structural damage.
The court held that it can be. Building on Sisbro, Inc. v. Industrial Comm’n, 207 Ill. 2d 193 (2003) — the leading Illinois case on aggravation of pre-existing conditions — the court reasoned that when a pre-existing asymptomatic condition becomes painful as a result of work-related activity, the symptomatic condition is itself a compensable aggravation, even in the absence of any organic or structural change. As the court explained, if a pre-existing condition that was previously silent suddenly becomes painful, something must have caused that change. When competent medical evidence shows that the something is the worker’s job duties, the resulting pain is a compensable injury under the Act.
The court was careful to apply the long-standing standard of proof. The petitioner did not have to prove that her work was the only cause or even the primary cause of her pain. Under Illinois law, it is enough to show that her work activities were a contributing factor. Because the Commission accepted the treating surgeon’s causation opinion, and that opinion was supported by the medical evidence, the appellate court found no basis to disturb the award.
It is worth noting that the decision was not unanimous. Justice Mullen dissented, arguing that the claimant had not produced medical evidence that her work duties actually aggravated or accelerated the underlying pathology — only that the duties caused pain. The dissent reflects an ongoing tension in this area of the law, and defense attorneys will likely continue to push the same arguments in future cases.
Why This Decision Matters to Injured Workers
Defense attorneys and insurance carriers frequently rely on the argument that an injured worker’s symptoms come from a pre-existing degenerative condition rather than from the job. That argument is even more common in repetitive trauma cases, where there is no single dramatic event to point to and where MRI findings often show some degree of age-related wear and tear. Tazewell County narrows one version of that defense.
Specifically, after this decision, an employer cannot defeat a claim simply by showing that the underlying tissue damage pre-dated the work activity or that the work did not change the underlying anatomy. If the worker’s job duties caused a previously asymptomatic condition to become painful — and the worker presents competent medical evidence supporting that link — the resulting condition is a compensable injury under the Act. The decision does not eliminate every pre-existing-condition defense. Employers can still argue that the symptoms are the natural progression of the underlying condition, that the work duties were not actually repetitive trauma, or that the medical opinions linking work to pain are not credible. But the structural-change argument standing alone is no longer a winning defense.
This is particularly significant in Illinois, where so many injured workers have demanding physical jobs in trades like construction, healthcare, manufacturing, warehousing, and skilled trades. Many adults over the age of forty have some degree of degenerative change visible on an MRI. The legal question is not whether the condition existed in some form before the job — it is whether the job duties caused the symptoms that now require medical care or time off work. Tazewell County keeps the focus where it belongs.
What Injured Workers Should Take Away From This Case
If you have suffered a work injury and your employer or its insurance carrier is pointing to a pre-existing condition as a reason to deny your claim, do not assume the denial is the end of the road. Under Tazewell County and the broader framework established by Sisbro, you may still be entitled to medical care, temporary total disability benefits, and a permanency award — provided you can prove that your work duties contributed to the painful symptoms and that the resulting treatment, time off work, and permanent impairment are causally related to your job.
What matters in these cases is the medical evidence. A clear, well-supported causation opinion from your treating physician — explaining how your specific job duties contributed to your specific symptoms — is often the difference between a denied claim and an awarded one. Insurance company examiners under Section 12 of the Act will frequently disagree, but the arbitrator and, ultimately, the Commission are entitled to weigh competing medical opinions and may credit your treater over the defense examiner. Detailed records, accurate descriptions of your job duties, and consistent reporting of your symptoms to your doctors all strengthen your position.
It is also worth remembering that Tazewell County does not mean every painful experience at work is automatically covered. The decision still requires competent medical evidence linking specific work activity to the symptomatic condition. But it does close off a line of defense that insurance carriers have used for years — the argument that pre-existing pathology automatically defeats a claim. Illinois law has long recognized aggravation of a pre-existing condition as a fully compensable injury. The fact that you had prior treatment, prior imaging, or prior diagnoses does not automatically defeat your claim. We have written before about how pre-existing conditions interact with Illinois workers’ compensation claims and how to prove that a repetitive strain injury is work-related. The Tazewell County decision builds on those principles and gives injured workers another tool to push back against denials grounded in pre-existing pathology.
If your workers’ compensation claim has been denied because the insurance company says your injury is the result of a pre-existing condition, the attorneys at The Law Offices of Millon & Peskin, Ltd. are here to help you protect your rights as an injured worker. We represent injured workers throughout the Chicagoland area, including DuPage, Cook, Will, Kane, and Lake counties, and we have decades of experience handling cases involving repetitive trauma, aggravation of pre-existing conditions, and disputed causation. Contact our office at 630-449-3884 for a free consultation to discuss your case.