Employee claims that he developed impingement syndrome with instability of the right shoulder as a result of the work-related accident of February 7, 2001. Employer contends that the employee sustained only rotator cuff tendonitis from the work-related injury and that his impingement syndrome developed as a result of a subsequent undisclosed accident or repetitive overhead activities.
The employee must establish a causal connection between the accident and the claimed injuries. Davies v. Carter Carburetor Div., 429 S.W.2d 738 (Mo. 1968); McGrath v. Satellite Sprinkler Systems, 877 S.W.2d 704, 708 (Mo. App. 1994); Blankenship v. Columbia Sportswear, 875 S.W.2d 937, 942 (Mo. App. 1994); Fisher v. Archdiocese of St. Louis, 793 S.W.2d 195, 198 (Mo. App. 1990); Cox v. General Motors Corp., 691 S.W.2d 294 (Mo. App. 1985); Griggs v. A.B. Chance Company, 503 S.W.2d 697, 703 (Mo. App. 1974); Smith v. Terminal Transfer Company, 372 S.W.2d 659, 664 (Mo. App. 1963).
Amendments made to Section 287.020 .2 in 1993 require that the injury be "clearly work related" for it to be compensable. An injury is clearly work related "if work was a substantial factor in the cause of the resulting medical condition or disability. An injury is not compensable merely because work was a triggering or precipitating factor." The Supreme Court held in Kasl v. Bristol Care, Inc., 984 S.W.2d 852 (Mo. 1999) that the foregoing language overruled the holdings in Wynn v. Navajo Freight Lines, Inc., 654 S.W.2d 87 (Mo. 1983), Bone v. Daniel Hamm Drayage Company, 449 S.W.2d 169 (Mo. 1970), and many other cases which had allowed an injury to be compensable so long as it was "triggered or precipitated" by work. Injuries which are triggered or precipitated by work may nevertheless be compensable if the work is found to be a "substantial factor" in causing the injury. Kasl, supra at 853. A substantial factor does not have to be the primary or most significant causative factor. Bloss v. Plastic Enterprises, 32 S.W.3d 666, 671 (Mo. App. 2000); Cahall v. Cahall, 963 S.W.2d 368, 372 (Mo. App. 1998). An accident may be both a triggering event and a substantial factor in causing an injury. Id. Subsection 2 also provides that an injury must be incidental and not independent of employment relationship and that "ordinary, gradual deterioration or progressive degeneration of the body caused by aging" is not compensable unless it "follows as an incident of employment." The extent to which the 1993 amendments have further modified prior caselaw will be determined by the appellate courts. See Cahall, supra at 372.
The quantum of proof is reasonable probability. Davies, supra at 749; Downing v. Willamette Industries, Inc., 895 S.W.2d 650, 655 (Mo. App. 1995); White v. Henderson Implement Co., 879 S.W.2d 575, 577 (Mo. App. 1994); Fischer at 199; Banner Iron Works v. Mordis, 664 S.W.2d 770, 773 (Mo. App. 1983);Griggs at 703. "Probable means founded on reason and experience which inclines the mind to believe but leaves room to doubt." Tate v. Southwestern Bell Telephone Co., 715 S.W.2d 326, 329 (Mo. App. 1986); Fischer at 198.
Such proof is made only by competent and substantial evidence. It may not rest on speculation. Griggs v. A. B. Chance Company, 503 S.W.2d 697, 703 (Mo. App. 1974). Expert testimony may be required where there are complicated medical issues. Goleman v. MCI Transporters, 844 S.W.2d 463, 466 (Mo. App. 1993); Griggs at 704; Downs v. A.C.F. Industries, Incorporated, 460 S.W.2d 293, 295-96 (Mo. App. 1970). Expert testimony is required where the cause and effect relationship between the claimed injury or condition and the alleged cause is not within the realm of common knowledge. McGrath v. Satellite Sprinkler Systems, 877 S.W.2d 704, 708 (Mo. App. 1994); Brundige v. Boehringer Ingelheim, 812 S.W.2d 200, 202 (Mo. App. 1991). Expert testimony is essential where the issue is whether a preexisting condition was aggravated by a subsequent injury. Modlin v. Sun Mark, Inc., 699 S.W.2d 5 (Mo. App. 1985). The fact finder may accept only part of the testimony of a medical expert and reject the remainder of it. Cole v. Best Motor Lines, 303 S.W.2d 170, 174
(Mo. App. 1957). Where the opinions of medical experts are in conflict, the fact finding body determines whose opinion is the most credible. Hawkins v. Emerson Electric Co., 676 S.W.2d 872, 877 (Mo. App. 1984). Where there are conflicting medical opinions, the fact finder may reject all or part of one party's expert testimony which it does not consider credible and accept as true the contrary testimony given by the other litigant's expert. Webber v. Chrysler Corp., 826 S.W.2d 51, 54 (Mo. App. 1992); Hutchinson v. Tri-State Motor Transit Co., 721 S.W.2d 158, 163 (Mo. App. 1986). An administrative law judge may not constitute himself or herself as an expert witness and substitute his or her personal opinion of medical causation of a complicated medical question for the uncontradicted testimony of a qualified medical expert. Wright v. Sports Associated, Inc., 887 S.W.2d 596 (Mo. 1994); Bruflat v. Mister Guy, Inc., 933 S.W.2d 829, 835 (Mo. App. 1996); Eubanks v. Poindexter Mechanical, 901 S.W.2d 246, 249-50 (