I.
The employee appeals from a pro forma judgment of the Superior Court which affirmed a decision of the Workers’ Compensation Commission denying the Petition for Award of Comjjensation.
The facts of the case are largely undisputed. Until August 14, 1979, the date assertedly commencing the period of total disability, the employee worked as a machinist for Masters Machine Co. On February 28,1978, the employee was in the course of his employment activities operating a drill-press. He was sitting on a stool, described to be twenty-five or twenty-six inches in height, which another employee accidentally kicked out from under him. Because his knees were “frozen” due to a pre-existing condition, the employee was unable to break his fall, and he fell from the stool directly onto the floor. He testified that he immediately experienced pain in his lower back, and that he sought medical assistance at a local hospital the next day when he developed substantial pain in his right hip. Medication provided by his physiсian, Dr. Belnap, was ineffective in relieving the pain which persisted and occasionally intensified. The employee nonetheless returned to work three days after his fall. He testified that the pain forced him to lose a week of work in November 1978, and that it ultimately compelled him to leave his employment on August 14, 1979. 1
Other testimony revealed the debilitating effects of the fall. The employee stated that he was able to work, climb stairs, lift heavy items, dance, swim, and drive pain *332 lessly until the incident of February 28. After the fall, however, he was unable to stoop, dance, swim, or climb stairs.. He also claims to have difficulty sleeping, and he now consumes forty aspirin a day. The sole issue presented develops from the employee’s medical condition preceding his fall from the stool on February 28, 1978. 2
By stipulation of the parties, the deposition of George Morton, a rheumatologist, was admitted in evidence before the Commissioner. Dr. Morton had examined the employee at the request of defendant-insurer. He diagnosed the employee as suffering from rheumatoid arthritis of the right hip, osteoarthritis at L4-5 and L5-S1, spon-dylolisthesis at L5-S1 (“a subluxation or partial dislocation of the fifth vertebra, fifth lumbar vertebra or the first sacral vertebra”), and spina bifida occulta at L5. The record shows that spina bifida occulta is a congenital disorder. The osteoarthritis is a condition which predated the February 1978 fall. The symptomatology of the os-teoarthritic condition was stated to have been “caused” by the employee’s fall from the stool. However, absent x-rays which would demonstrate the extent of this condition as it existed before February 1978, Dr. Morton was unable to determine whether the fall affected any underlying pathology.
Similarly, while spondylolisthesis can be caused by trauma, Dr. Morton was unable to identify a causal relation between that condition and the employee’s accident because оf the absence of records made before the accident. He also testified that, as with osteoarthritis, quiescent spondylolisthesis may become symptomatic upon trauma. In fact, Dr. Morton testified that if the employee had been affected with asymptomatic spondylolisthesis before February 1978, the accident might well have revealed symptomatic manifestations of the condition.
Finally, the medical report prepared by Dr. Thomas Martin, a specialist in orthopedic surgery, was admitted into evidence, in which Martin diagnosed the employee as suffering from noncongenital degenerative disc disease in L5-S1.
The Commissioner’s decree made several pertinent findings.
3
He found that the employee is totally disabled. He found that “the employee did fall off a stoll [s/c] at work under circumstances making that injury compensable as against Masters Machine.” Presumably, this means that the injury arose out of and in the course of employment.
See
39 M.R.S.A, § 51. The Commissioner then considered the employee’s bаck condition and found that the os
*333
teoarthritis, degenerative disc disease, spon-dylolisthesis,
4
and spina bifida occulta were asymptomatic prior to February 28, 1978. He found that the accident rendered these conditions symptomatic. The Commissioner then concluded that falling from the stool effected no change in the underlying pathology of the employee’s back.
5
Construing
Hamm v. University of Maine,
Me.,
Pursuant to the employee’s subsequent motion for findings of fact and conclusions of law, the Commissioner made clear that the employee’s congenital and degenerative conditions were not caused by the fall, but that they were rendered symptomatic by it. The employee obtained a pro forma decree in a timely manner from which he now seasonably appeals.
We conclude that the Commissioner committed an error of law in construing Hamm to preclude, as a general proposition, the compensability of a disability resulting from “the mere creation of pain and swelling.” He further erred in concluding on the basis of the application of that erroneous principle of law that the employee here had failed, on this record, to carry his burden of demonstrating that the fall from the stool resulted in an injury to the employee’s lumbo-sacral spine which “arose out of” his employment.
II.
The issue of causal connection between employment activity and disability is one of fact.
Bruton v. City of Bath,
Me.,
It must be borne in mind that the original purpose of the Workers’ Compensation Act was “to compensate employees for injuries suffered
while
and
because
they were at work.” (Emphasis added.)
Canning v. State Department of Transportation,
Me.,
It would be anomalous to construe the causation requirement of the Act, after the restrictive element of accidental injury has been eliminated, in its application to the so-called “aggravation” cases so as to make the overall impact of the amended causation requirement more stringent than it was in its original form, absent a clearly discernible legislative intent compelling such a construction.
It must, however, be borne constantly in mind that the purpose of the “arising out of” language, as used in the Act, is to establish a requirement of causation between the employee’s work activity and his ultimate disability.
See Bruton
v.
City of Bath,
Me.,
In a series of cases dating back to 1919, this Court has followed what has become a well-settled rule of compensation law that when a work-related incident or exertion “lights up” or activates disabling effects of a pre-existing disease condition which was previously asymptomatic, the disability resulting from such activation of symptoms is compensable.
See, e.g., Wood v. Cives Construction Corp.,
Me.,
*335 On appeal, we noted that because of the effect of the approved agreement, the employee’s existing disability was to be treated as adjudicated to result from the work-related fall and therefore to be compensable until the employer demonstrated by a preponderance of the evidence “that the effect of the accident has ended.” Id. at 921. We stated that the disability “would continue to be compensable:
(1) If the fall is the sole cause of the present incapacity.
(2) If the fall caused or precipitated the neurological disorder or if the neurological disorder existed before the fall and was aggravated by the fall... .
(3) If effects of the fall and of the neurological disorder combine to produce the incapacity. ...”
Id. at 921-22. We said the employer’s burden required it to negative all three of these propositions in order to achieve a termination of compensation. In the absence of any medical knowledge as to the physiological cause of motor neuron disease and with evidence in the record that the employee’s symptoms could be the result of pre-existing cervical arthritis “lighted up” by the fall, we concluded that the evidence was insufficient to show a termination of the effects of the fall in producing the existing disability.
Soucy,
We applied these substantive principles of law in the context of the burden of proof requirements of an employee’s petition for award in
Canning,
An employee is, of course, entitled to compensation for a disability proximately caused by his employment regardless of whether his condition at the time of injury was average or subnormal. Thus, a work injury that aggravates a pre-exist-.ing condition is compensable even though a physically normal employee would have been unaffected, provided the injury occurs under conditions that would otherwise entitle the employee to compensation.
These cases reiterate the previously established law that an employee is entitled to disability compensation for any period of disability that is shown to result from the combined effects of work-related activity and a pre-existing condition of the employee.
Canning,
What those cases do not directly address is the content of the proper test of causation and the method of its application in cases where the disability for which compensation is sought results from the “combined effects” of a work-related risk and a “personal risk” of the employee created by a pre-existing condition (or susceptibility to disability) which is not work-related. Those cases and previous cases spoke only to the general issue, which was all that was before *336 the Court in those cases, of whether a disability caused by such combined effects was a compensable “injury” for purposes of the application of the “arising out оf” language of the Act. We have not addressed the particular concept of causation, or its content, which is to be applied to distinguish those cases in which the “injury” is sustained by an employee only while at work but not because of his work activity, from those cases where the injury is sustained both while and because the employee is engaged in the work activity. In the former, the injury does not result in compensa-bility while in the latter it does.
Some of our subsequent cases have turned on considerations of the content of the causation requirement, but they have been few in number and have not presented an occasion for the comprehensive articulation of the nature and content of the causation requirement in the so-called “combined effects” case. This case does present an occasion wherein such articulation is necessary to a reasoned decision of the issues before us as they are so nicely and deliberately postured by the Commissioner. The Commissioner’s erroneous interpretation of our recent cases on the point, here manifested, provides further impetus to set out in greater detail the underlying concept of the causation requirement.
That requirement is intended to result in the implementation of the general legislative intent under section 51 and section 52 of the Act that an employee who incurs a disability
while
and
because
he is at work receive compensation for it.
See Canning,
Absent the content provided by “legal cause,” the causation requirement of the statute would allow compensation for any disability that could be shown as a matter of medical or physical fact to have occurred because of the effect of ordinary
*337
activity upon a pre-existing condition during the course of employment. Such was clearly not the intent of the Legislature in using the “arising out of” language. It was intended that compensation should be available only where disability results from some sufficient causal relationship to the conditions under which the employee works.
See Canning,
In
Barrett v. Herbert Engineering, Inc.,
Me.,
It is true that the employer takes the employee as he finds him, but, even so, where the employee already suffers from a preexisting infirmity in dormant stage its activation or exacerbation from an asymptomatic condition to a symptomatic one during the course of the employment is not compensable under our Workers’ Compensation Act unless the flare up arises out of the employment, meaning that it must be traced to the employment as a contributing proximate cause and not be solely due to a hazard to which the workman would have been equally exposed to apart from the employment.
The statutory words ‘arising out of’ mean that there must be some causal connection between the conditions under which the employee worked and the injury which arose, or that the injury, in some proximate way, had its origin, its source, its cause in the employment.
In
McLaren,
A similar analysis to that used in
Barrett
and
McLaren
was employed in
Parent v. Great Northern Paper Co.,
Me.,
We there concluded that the Commissioner was justified, on the evidence, in concluding that the disability resulted solely from the condition and not from the lifting activity. The Parent case thus represents an *339 application of the “medical cause” requirement. There, as opposed to the situations in Barrett and McLaren, there was an absence of proof that the inflammation resulted in pain, in a medical-factual sense, because of any effect of the work-related, lifting activity. Hence, the work activity was not shown to be a sufficient medical cause of the symptomatology resulting in an increased level of disability.
III.
The cases in
Hamm v. University of Maine,
Me.,
In
Hamm,
the work activity prompting the “flare up” of symptoms from the employee’s underlying non-work-related condition necessarily took place in the period from late September 1977 to November 4, 1977 when she stopped work. She returned to work nearly two years later as a telephone operator for a different employer, the Maine Air National Guard, on November 1, 1979. Two months after that, she left the new employment because of pain allegedly experienced as a result of the activity required of her
in the new employment.
She then sought compensation from the prior employer (University of Maine) on the factual premise that the work activity occurring between late September and November 4 of 1977 activated the symptoms of the underlying condition and disabled her after November 4,1977. The Commissioner so found, awarding compensation for total disability from November 5, 1977 to May 1, 1978 and at 50% disability from May 2,1978 to the date of the decree.
10
Hamm,
On appeal, the employer contended that the award was improper because there was no evidence to show that any disability Mrs. Hamm suffered after November 4,1977, resulted from the combined effects of her condition and the wоrk activity required of her between late September and November 4, 1977; in short, her disability after November 4, 1977 was solely the result of her condition pre-existing that period of employment, unaffected by any work activity. We concluded that the evidence did not support any Commission finding of a disability continuing after that date as arising out of the combined effects of the pre-exist-ing condition and the work activity. We said that to establish a compensable disability in that period it had to be shown that “the physical condition that impairs [Mrs. Hamm’s] earning capacity must have been caused or at least made worse by the performance of the job at the University.” Hamm, at 550.
We there recognized the absence of “legal cause.” We found the record to support only the conclusion that the underlying condition was the result of her pre-employment injuries and the surgery necessitated by them. The record there showed that her work activity in the course of her job at the University, chopping salad, produced exactly the same symptomatological results as did her everyday, non-work-related, domestic activities. Thus, while there was no question but that the work activity generated, as a matter of medical fact, the onset of her symptoms (thus satisfying “medical cause”) *340 it did not occur because of any increased risk peculiar to her work. She sustained symptoms from any similar activity as a risk of everyday non-employment life. Thus, the disability did not “arise out of” her employment.
We did not focus on the fact that her disability arose from the onset of “pain and swelling” except to show that the element of “medical cause” was satisfied
(e.g.,
that as a medical fact the chopping of salad produced or contributed to producing her symptoms and the resulting disability). The decision turned on the conclusion that “legal cause" was not present
(e.g.,
that the performance of that activity as part of her employment did not incrеase the risk of the occurrence of disability beyond the risk of her everyday activity). This is a far cry from any pronouncement, as found by the Commissioner in this case, that “pain and swelling may not constitute a compensable injury.”
11
The holding in that case is simply a recognition that “... if the deterioration [of the employee’s condition] is merely a resumption of the progression of the condition predating the industrial injury, further damage is not compensable.” 1B Larson,
supra,
§ 38.83, at 7-261-62.
See Greene v. Yeager,
In
Parlin
v.
G. H. Bass & Co.,
Me.,
*341
The medical evidence established unequivocally that Mrs. Parlin had been left, as a result of the prior work incident (and the surgery resulting therefrom), with a continuing condition of her hand and wrist diagnosed as “chronic recurring tenosynovi-tis of the de Quervain’s type.”
Parlin,
We have only recently said that proof that routine work activity causes activation of symptoms consisting of disabling pain is not sufficient to carry the employee’s burden on a petition for award where a pre-existing level of disability exists independently of any work-related activity or event.
See Brough v. Bell Pike Northeast,
Me.,
Any symptom, pain or otherwise, which arises out of an increased risk of the employment because of its relation to an incident or activity in the course of employment and results in an increased level of disability by activation of a previously quiescent disease condition, creates a com-pensable disability whatever may be the specific nature of the symptoms. The Commissioner here erred in putting the focus of the inquiry on the nature of the symptoms (i.e., pain and swelling) producing the disability. He ignored the truly operative fact: whether some risk-enhancing incident or activity that was work-related combined with the effects of the condition of the employee’s back to produce an increase in the level of disability. 14 If it did, the employee is entitled to compensation. The exact mechanics by which the incident or activity produces the increase in disability (that is, whether by production of pain, restriction of motion or swelling) is not controlling. The operative fact is the existence of a causative connection between the work-related incident or activity and an increase in the pre-existing level of disability that meets the tests of both medical and legal causation.
IV.
In the present case, on the basis of the Commissioner’s very explicit findings, it is clear that this Petitioner is entitled to compensation for disability resulting from an injury arising out of his еmployment. He specifically found that the condition of the employee’s lumbar spine was asympto *343 matic prior to the time that he fell from the stool at work. He further found that a combination of the effects of the fall and the pre-existing condition of arthritis of the cervical spine produced pain and that the effect of that pain was to disable the employee. Thus, the requirements of “medical cause” are met here.
The controlling question in this case is whether the event precipitating the onset of his symptoms (e.g., the fall from the stool) meets the requirements of “legal cause” in that it results from a risk attributable to the work activity of the employee. A traumatic event resulting from the employee’s work activity clearly does meet that requirement. The Commissioner properly so found on the facts of this case. The employee was sitting on a stool in the presence of other employees moving around in his work envirоnment in order to do his work. Thus, his risk of sustaining a fall under those circumstances was increased by the conditions of his work environment above those that existed in a normal, non-employment day. It is sufficient to establish causality that it was proven that the fall was the product of a work-related risk and that the end result of the materialization of that risk was the production of pain which disabled him. His entitlement to compensation is not defeated either because it was pain which produced his disability or that the disability arose out of the “combined effects” of his fall and the pre-exist-ing condition of his back.
The entry will be:
The pro forma decree of the Superior Court is reversed and the case is remanded to the Workers’ Compensation Commission for further proceedings consistent with this opinion.
Further ordered that the employer pay to the employee an allowance for counsel fees in the amount of $550.00, together with his reasonable out-of-pocket expenses for this appeal.
All concurring.
Notes
. During this period, other employees assisted the plaintiff in performing tasks which he was unable to do because of his condition.
. The employee was involved in two rather serious accidents in 1960 and 1961. The effects of these events led in part to his condition in February 1978.
. The employee’s Petition for Award of Compensation initially sought compensation for disability resulting from aggravation, as the result of the fall, of an arthritic condition of his hip. Medical testimony before the Commissioner indicated that prior to the fall at work the employee suffered from “[v]ery severe degenerative arthritis at his right hip.” Dr. John Wick-enden was of the opinion that the disease was too severe to have developed in the interim .period between the date of the fall at work and August 9, 1979, the date of the doctor’s first examination of the employee. He further testified that “some portion” of the employee’s symptomatology arising from this condition was attributable to the fall but estimated that any additional pathology resulting from the fall would amount to only about 1%. Dr. Morton also noted that a new hip had been implanted in the employee in March 1980. As a result, the employee became able to sit and stand in relative comfort. Morton thought that the correction of the arthritic hip condition removed some stress from the lower back, thereby reducing the pain.
The Commissioner found as a fact that no disability arose from any trauma sustained in the fall to the employee’s right hip. He then went on to consider the compensability of the disability arising out of aggravation of the preexisting condition of the employee’s back. On the basis of the fact-finding and principles of law indicated in the text, he found that disability not to be compensable. On appeal, the employee has made no attack on the Commissioner’s handling of the claim for disability arising out of the condition of the employeе’s right hip. Therefore, no issue as to that claim is before us and we intimate no opinion on any aspect of that particular claim.
The claim for disability resulting from the effect of the fall at work upon the employee’s back was placed before the Commissioner by an amendment to the original Petition.
. The Commissioner characterized this as a congenital condition, but the testimony indicated otherwise. See text supra at 332. This appears, however, to have little effect on the analysis here, as the finding carries importance only to the extent that the condition antedated the accident.
. He stated that there was no testimony on this point. This observation, however, is incorrect. Dr. Morton stated, as the Commissioner speculated, that the effect on the employee’s pathology as to osteoarthritis and spondylolisthesis could not be determined.
. The “by accident” requirement was removed from the first and second paragraphs оf § 52 of the Act by P.L.1973, ch. 389 (effective October 3, 1973). That section provided for benefits consisting of reasonable medical aids and services and rehabilitation at the employer’s expense for any work-related injury. The legislation made no change with respect to the “by accident” requirement in 39 M.R.S.A. § 51 which provides for payment of disability benefits for such injuries. This Court, nevertheless, held that the failure to make such a change in § 51 concurrently with that accomplished in § 52 was a legislative oversight and that the effect of P.L.1973, ch. 389 was to remove from the Act the “by accident” requirement for entitlement to disability benefits under § 51.
Canning
v.
State Department of Transportation,
Me.,
. That case arose out of the employer’s petition for review of incapacity alleging that the disability for which the employee was receiving compensation under a prior, approved agreеment for payment of compensation had diminished or ended. Thus, the employer there bore the burden of proof.
Soucy,
. Professor Larson derives his mode of analysis principally from various cases in which the injury is some type of heart attack. He notes, however, that there is “no reason” why the formula so derived cannot be successfully applied in other types of cases involving the combined effects ' of pre-existing conditions and work-related activity. IB Larson, supra, § 38.-83, at 7-249.
. See,
e.g., Brawn v. St. Regis Paper Co.,
Me.,
. The Commissioner excluded from the period of compensability the approximately two-month period during which the employee was actually employed as a telephone operator for the Maine Air National Guard.
. The Commissioner here found that the employee’s fall effected “no change in the underlying pathology of the employee’s back.”
See supra
at 333. To the extent that he attached any dispositive significance to this finding in evaluating the sufficiency of the evidence here to meet the causal requirement of § 51, he committed further error. This is pointed up by three observations. First, there is no mention in the opinion in either
Hamm,
. Because of a procedural irregularity, the employee was not permitted, on appeal, to challenge that part of the Commission decree that found no causal relation between the employment at Bennett and her disability. The employee’s claim against each employer was commenced before the Commission by the appropriate petition and the cases, though not consolidated, were heard together by the Commissioner. The ultimate result of the proceedings before the Commission was entry of a decree which required Bass to pay compensation, “but did not make any express disposition of Mrs. Parlin’s petition seeking further compensation from Bennett.”
Parlin,
. We advert to a further issue which the Commissioner may confront on remand. Under the present law of Maine, where in a “combined effects” case total disability results, the employer is liable for compensation for total disability “. .. irrespective of whether the incapacity may have been due in part to the prior condition.”
Gagnon's Case, 144
Me. 131, 134,
If an employee who had a permanent impairment from any cause or origin which is, or is likely to be, a hinderance of obstacle to his employment, sustains a personal injury arising out of and in the course of employment which, in combination with the earlier preexisting impairment results in a total permanent incapacity, the employer or his insurance carrier is liable for all compensation provided by this section. The employer or insurance carrier shall be reimbursed from the Second Injury Fund for compensation payments not attributable to the second injury.
P.L.1981, ch. 474, § 1. On remand, it may be necessary for the Commissioner to consider the application of this statutory language to the facts of this case. We intimate no opinion on any issue that may be raised in such an eventuality.
. That error might have been avoided by a careful reading of the opinion in the recent case of
Axelsen v. S. D. Warren, Div. of Scott Paper Co.,
Me.,
We interpret this language of the Commission to signify that the Commission decided the worker had failed to meet the ultimate burden of proof resting on him to show that it was more probable than not that special work-related conditions, rather than the worker’s routine use of the foot as occurring whether or not the worker was engaged in performing his job, had caused the incapacity at issue.
Axelsen,
Dr. Labelle stated that the worker’s now existing condition resulted from the passage of time in combination with the original injury and that, further, it could not be said that the heavy work shoes had causal relation to the present condition of the worker’s left foot. Expert evidence is thus lacking to show that it was more probable than not that work-related circumstances, newly arising, had causally contributed to the workers’ incapacity here at issue.
Id. (Emphasis in original.) A clearer, cleaner application of the requirement of “legal cause” would be difficult to imagine.