## Facts

- Frederick J. Klosterman suffered a compensable workplace injury to his left knee and underwent surgery.
- Months later, while playing frisbee, he jumped, landed on his right leg, had a minor collision, and tore a ligament in the same (left) knee.
- Klosterman sought workers’ compensation benefits for the later injury, asserting it resulted from weakness caused by the original industrial injury and surgery.
- The carrier denied liability, asserting the frisbee injury was a new, independent, non-industrial injury.
- Klosterman’s treating physician testified that the frisbee incident precipitated the tear but that, but for the prior industrial injury and residual weakening, the tear would not have occurred.
- No contrary medical testimony was presented.
- The administrative law judge (ALJ) found the frisbee incident caused the later injury and treated it as a new, noncompensable injury; the ALJ made no findings on whether playing frisbee was unreasonable or constituted an independent intervening cause.
- The Industrial Commission affirmed on administrative review, and Klosterman sought appellate review.

## Issues

1. Whether a later knee injury sustained during recreational activity is compensable as a consequence of an earlier compensable industrial injury when uncontroverted medical testimony shows the earlier injury materially contributed to the later injury.
2. Whether the Commission erred by denying compensability without applying the compensable-consequence doctrine and without findings on independent intervening cause or the reasonableness of the claimant’s conduct.

## Decision

- The Arizona Court of Appeals set aside the Industrial Commission’s award denying compensation.
- The court held the award was legally unsupportable because it disregarded uncontroverted medical evidence connecting the later injury to the original industrial injury and failed to address whether the causal chain was broken by an independent intervening cause.

## Legal Principles

- An employer/carrier is liable for later injuries that are the direct and natural result of a compensable industrial injury unless an independent intervening cause breaks the causal chain.
- When medical causation is at issue, the Commission generally must rely on competent medical testimony; it may not arbitrarily reject uncontroverted medical testimony that is not inherently improbable.
- A claimant’s post-injury conduct breaks causation only if it is so unreasonable, in light of the condition, that it constitutes an independent intervening cause; ordinary activities generally do not sever compensability absent such a showing.
- Denying compensability for a subsequent injury requires application of the correct causal framework, including analysis of intervening cause where implicated by the parties’ theories and the record.

## Conclusion

The court set aside the denial of benefits because the only medical evidence established that the original compensable knee injury materially contributed to the later ligament tear, and the Commission neither applied the compensable-consequence doctrine nor made findings that the claimant’s recreational activity was an independent intervening cause.


Klosterman v. Indus. Comm’n of Ariz., 155 Ariz. 435, 747 P.2d 596 (Ct. App. 1987)