ADJ15615310 · June 1, 2026

The Appeals Board found Dr. Mack's apportionment opinion was not substantial evidence as it lacked required detailed explanation and reasoning, thus denying apportionment and awarding an unapportioned permanent disability.

From the decision · page 15Dr. Mack's apportionment opinion fails to satisfy the requirements as set forth in Escobedo6. His analysis relies primarily on the timing of Applicant's employment and the existence of pre-existing conditions, without explaining "how and why" those conditions are causing permanent disability at the time of the evaluation. As explained in Escobedo, a medical opinion on apportionment must do more than state percentages. It must explain the causal relationship between the industrial injury and the permanent disability and separately explain how and why nonindustrial factors are responsible for a portion of that disability. Dr. Mack's reports do not provide this required analysis. The deficiency is also apparent with respect to the cubital tunnel syndrome. While Dr. Mack relates this condition to the elbow pathology, he does not explain why 50% of the resulting disability is attributable to nonindustrial factors or identify what those factors are. A mere medical relationship between conditions does not establish apportionment. Because Defendant bears the burden of proof on apportionment, and because the medical evidence offered does not constitute substantial evidence, the Court is not permitted to rely upon it. Accordingly, an unapportioned award is warranted.

The Appeals Board found that the applicant did not have knowledge of disability within the meaning of section 5412 until January 3, 2022, and thus the statute of limitations did not bar the claim.

From the decision · page 12III DISCUSSION: STATUTE OF LIMITATIONS Defendant asserts that Applicant's cumulative trauma claim is barred by the statute of limitations pursuant to Labor Code sections 5405 and 5412, asserting that the date of injury occurred no later than July 27, 2018, when Applicant was released from his final professional baseball team. Defendant relies on the retrospective opinion of QME, Dr. Mack, who opined that

Applicant filed the Application for Adjudication of Claim on January 3, 2022, alleging injurious exposure and injuries contributing to disability.

Favours Applicant prevailed

This established the section 5412 date of injury and knowledge of disability, starting the statute of limitations period.

From the decision · page 5In this case, we agree with the WCJ that defendant did not meet it burden to show the concurrence of knowledge and disability in 2018. However, we attribute knowledge to applicant once he filed the Application for Adjudication of Claim on January 3, 2022 alleging "PLAYING AND PRACTICING PROFESSIONAL BASEBALL. APPLICANT HAD INJURIOUS EXPOSURE AND INJURIES IN CALIFORNIA THAT CONTRIBUTED TO HIS DISABILITY.." (Old Republic Insurance v. Workers' Comp. Appeals Bd. (2000) 85 Cal.Comp.Cases 504 (writ den.) Therefore, we find the section 5412 date of injury to be January 3, 2022 and will amend the WCJ's decision accordingly.

Applicant's contemporaneous medical records at separation showed no disability despite symptoms and treatment.

Favours Applicant prevailed

This supported the finding that the statute of limitations did not commence at separation because there was no compensable disability then.

From the decision · page 13Defendant blurs the distinction between injury, pain, symptoms, treatment, loss of elite performance, and disability under Labor Code section 5412. The evidence establishes that, during his playing career, Applicant experienced pain, underwent treatment, and sustained multiple orthopedic conditions. However, such evidence demonstrates, at most, knowledge of injury, not knowledge of disability within the meaning of section 5412. Critically, the contemporaneous medical records at the time of Applicant's separation from employment affirmatively establishes the absence of disability. The 2017 and 2018 exit physicals specifically concluded that Applicant had no impairment, no permanent disability and was capable of full work without restrictions. Accordingly, even if Applicant was aware of ongoing symptoms, the record does not establish that he sustained compensable disability at that time. Without disability, the statutory requirements of section 5412 were not met, and the statute of limitations did not commence.

Dr. Mack's apportionment opinion lacked detailed explanation and reasoning required by Escobedo and was not substantial evidence.

Favours Applicant prevailed

This led to denial of apportionment and an unapportioned permanent disability award.

From the decision · page 15Dr. Mack's apportionment opinion fails to satisfy the requirements as set forth in Escobedo6. His analysis relies primarily on the timing of Applicant's employment and the existence of pre-existing conditions, without explaining "how and why" those conditions are causing permanent disability at the time of the evaluation. As explained in Escobedo, a medical opinion on apportionment must do more than state percentages. It must explain the causal relationship between the industrial injury and the permanent disability and separately explain how and why nonindustrial factors are responsible for a portion of that disability. Dr. Mack's reports do not provide this required analysis. The deficiency is also apparent with respect to the cubital tunnel syndrome. While Dr. Mack relates this condition to the elbow pathology, he does not explain why 50% of the resulting disability is attributable to nonindustrial factors or identify what those factors are. A mere medical relationship between conditions does not establish apportionment. Because Defendant bears the burden of proof on apportionment, and because the medical evidence offered does not constitute substantial evidence, the Court is not permitted to rely upon it. Accordingly, an unapportioned award is warranted.

Dr. Mack opined that the applicant's disability onset was July 27, 2018, and apportioned 50% of right elbow residuals to nonindustrial factors and 50% to industrial cumulative trauma, but his apportionment opinion was found not to be substantial evidence due to lack of detailed explanation.

Dr. Mack's apportionment opinion lacked detailed explanation and reasoning required by Escobedo, thus was rejected as substantial evidence.

From the decision · page 11With regard to the right elbow, residuals are due 50% to an underlying condition requiring arthroscopic debridement before his professional career. Further aggravation (25%) occurred in the 2013 timeframe. His present state of arthrosis reflects additional trauma through 2018 (25%). Regarding his upper extremity numbness and nerve irritability, the patient reports that his complaints of numbness on the right side began in 2017 or 2018 but that he had occasional symptoms as early as 2012, prior to his second right elbow surgery.

Escobedo v. Marshalls (2005) 70 Cal. Comp. Cases 604 (Appeals Bd. en banc)

A medical opinion on apportionment must be framed in terms of reasonable medical probability, not speculative, based on pertinent facts and adequate examination, and must set forth reasoning supporting its conclusions.

Applied to reject Dr. Mack's apportionment opinion as not substantial evidence.

From the decision · page 15Dr. Mack's apportionment opinion fails to satisfy the requirements as set forth in Escobedo6. His analysis relies primarily on the timing of Applicant's employment and the existence of pre-existing conditions, without explaining "how and why" those conditions are causing permanent disability at the time of the evaluation. As explained in Escobedo, a medical opinion on apportionment must do more than state percentages. It must explain the causal relationship between the industrial injury and the permanent disability and separately explain how and why nonindustrial factors are responsible for a portion of that disability. Dr. Mack's reports do not provide this required analysis. The deficiency is also apparent with respect to the cubital tunnel syndrome. While Dr. Mack relates this condition to the elbow pathology, he does not explain why 50% of the resulting disability is attributable to nonindustrial factors or identify what those factors are. A mere medical relationship between conditions does not establish apportionment. Because Defendant bears the burden of proof on apportionment, and because the medical evidence offered does not constitute substantial evidence, the Court is not permitted to rely upon it. Accordingly, an unapportioned award is warranted.

Applicant's contemporaneous medical records at separation showed no disability despite symptoms and treatment, supporting that the statute of limitations did not commence at separation.

From the decision · page 13Defendant blurs the distinction between injury, pain, symptoms, treatment, loss of elite performance, and disability under Labor Code section 5412. The evidence establishes that, during his playing career, Applicant experienced pain, underwent treatment, and sustained multiple orthopedic conditions. However, such evidence demonstrates, at most, knowledge of injury, not knowledge of disability within the meaning of section 5412. Critically, the contemporaneous medical records at the time of Applicant's separation from employment affirmatively establishes the absence of disability. The 2017 and 2018 exit physicals specifically concluded that Applicant had no impairment, no permanent disability and was capable of full work without restrictions. Accordingly, even if Applicant was aware of ongoing symptoms, the record does not establish that he sustained compensable disability at that time. Without disability, the statutory requirements of section 5412 were not met, and the statute of limitations did not commence.

Applicant's testimony that he did not always know when he was injured or healthy, and that soreness could be mistaken for injury, supported the finding that knowledge of disability was not established until 2022.

From the decision · page 10Notably, Applicant testified that he did not always know the difference between when he was healthy or injured because sometimes, he was sore after throwing which could be mistaken for an injury. (MOH/SOE 9/30/2025 at p. 3:13-15). His right knee started to bother him in 2015, about the same time as his right toe and he associated the two because he had to change how he walked. (Id. at p. 4:19-22).