A recent Maryland Court of Special Appeals decision, Washington Metropolitan Area Transit Authority v. Williams, 2012 Md. App. LEXIS 46 (Md. Ct. Spec. App. 2012) has clarified the status of the law in Maryland with respect to the causal relationship required to demonstrate that a second injury (which is not physically related to the original injury, such as where a knee injury causes back pain) is causally related to an original injury, and thereby compensable.
Jan Williams, the claimant, was a mechanic for WMATA and was working for his employer in 2008 when he injured his back and left knee on the job. In March of 2009, Mr. Williams was injured while returning from lunch to physical rehabilitation for the first injury when a driver backed into him, causing injury to Williams' right knee. The Maryland Workers' Compensation Commission found the second injury to be causally related to the original injury, and the Maryland Circuit Court for Prince George's County affirmed that finding. However, the Court of Special Appeals reversed, and found that the second injury was not causally related to the original injury.
WMATA relied upon a 1996 Maryland Court of Appeals decision, Mackin v. Harris, 342 Md. 1 (1996) in support of its assertion that the second injury was not causally related to the original injury. In Mackin, the employee had slipped and fallen on a patch of ice on his way to obtain physical therapy for a work-related injury. Id. at p. 2-3. The Mackin court noted that for a subsequent injury to be compensable, it must be the "direct and material result of a compensable primary injury." Id. at 7. The Mackin court went on to note that while Professor Lex. K. Larson, a noted authority in the field of Workers Compensation law, advocated a "but-for causation" approach to the issue, the Mackin court felt this was too broad a standard, and that acceptance of that standard "leads to rather extraordinary results." Id. at p. 9.
The Williams court found that while the Prince George's County Circuit Court had utilized Mackin in its analysis of the issue, the Circuit Court had missed the fact that the Mackin court advocated for a much more narrow standard-- namely, that the subsequent injury must have been a "direct causal connection" between the original compensable injury and the subsequent injury in order to have been proximately caused by the original injury. 2012 Md. App. LEXIS at p. 11. Using that standard, the Williams court concluded that Mr. Williams second injury directly resulted from a cause unrelated to the first injury-- namely, the driver's actions in striking Mr. Williams with his car in the parking lot. Id. at p. 12. Because the driver's actions had no connection whatsoever to the original injury, there was no proximate cause between the original injury and the subsequent injury. (Had the same situation been presented using the "but-for" standard of causation, the claim would arguably have been compensable-- as but for the original injury, Mr. Williams would not have been in the parking lot and would not have been struck.)
While the Court reversed the Circuit Court's findings, it remanded the matter in order to resolve a different issue-- whether the subsequent injury would be compensable as a new work-related injury, standing alone. As such, the matter was remanded to the Maryland Workers' Compensation Commission to determine that issue.