Legal Update: AMA Guides After Koeller
July 9, 2026
Beyond clavicle excisions, Koeller provides important guidance on interpreting the AMA Guides in Iowa workers' compensation.
By: Thania Rios
On 5/15/2026, the Supreme Court of Iowa issued a decision in Koeller v. Cardinal Logistics Mgmt. Corp. The immediate impact of this decision—specifically, that distal clavicle excisions are now worth 28-30 more weeks of PPD in Iowa—was addressed in a prior post. However, the decision also has broader implications for how the AMA Guides are used in workers’ compensation cases that are worth examining.
In the Koeller decision, the Supreme Court begins its legal analysis by observing that Iowa Code section 85.34(2)(x) effectively gives the AMA Guides (5th Ed.) the force of law—and that neither lay testimony or agency expertise can be used to modify permanent impairment ratings that have been assigned in accordance with the AMA Guides. This means that the “testimony…of an injured worker…cannot be boost a rating above the highest rating given by expert testimony.” Koeller, 35 N.W.3d 335, 342 (Iowa 2026). Likewise, “surveillance…cannot be used to lower a rating below the lowest rating given by expert testimony.” Id. Additionally, while the commissioner is entitled to choose among expert opinions offering different interpretations of the AMA Guides, “the commissioner should not supplant the role of the experts.” Id.
When it comes to the role of the commissioner in Agency hearings, the Supreme Court was clear: since “the AMA Guides have the force of law,” and “what the law requires is ultimately for the agency and the courts to decide,” ambiguities in the AMA Guides can be resolved by courts using “the usual interpretative tools that judges normally apply.” Id. Phrased more simply, the Koeller decision states that the AMA Guides are subject to statutory interpretation. In Koeller, the Court uses Iowa Code section 4.7 to resolve a contradiction between two contradictory sections of the Guides.
The Supreme Court is also clear about the role of expert witnesses, and how the commissioner can use their opinions. Under Iowa Code section 85.34(2)(x), the commissioner has the authority to “reconsider” what experts claim that “the AMA Guides” require. Id. at 343. While the commissioner cannot supplant the role of a medical expert in altering his medical opinions, he can apply “his interpretation of the governing law—the AMA Guides—to [the medical expert]’s factual determinations.” Id.
In addition to modifying the rules regarding how distal clavicle excisions are compensated, the Koeller decision also does much to clarify how the AMA Guides are supposed to be used in Iowa courts. As such, it will likely do much to shape how workers’ compensation cases are litigated moving forward.
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