Citation Nr: 21036363 Decision Date: 06/14/21 Archive Date: 06/14/21 DOCKET NO. 16-10 778 DATE: June 14, 2021 ORDER Entitlement to service connection for a cervical spine disability to include degenerative disc disease as secondary to bilateral knee degenerative joint disease is denied. Entitlement to service connection for bilateral thumb degenerative joint disease as secondary to bilateral knee degenerative joint disease is denied. Entitlement to service connection for left little finger degenerative joint disease as secondary to bilateral knee degenerative joint disease is denied. FINDINGS OF FACT 1. A cervical spine disability was not shown in service, did not manifest to a compensable degree within one year of service separation, is not otherwise related to service and is not caused or aggravated by a service-connected disability. 2. A bilateral thumb disability was not shown in service, did not manifest to a compensable degree within one year of service separation, is not otherwise related to service and is not caused or aggravated by a service-connected disability. 3. A little left finger disability was not shown in service, did not manifest to a compensable degree within one year of service separation, is not otherwise related to service and is not caused or aggravated by a service-connected disability. CONCLUSIONS OF LAW 1. A cervical spine disability was not incurred in service, nor may it be presumed to have been incurred in service. 38 U.S.C. §§ 1101, 1110, 1112, 1113, 1116, 1131, 5103, 5103(A) (2012); 38 C.F.R. §§ 3.303, 3.307, 3.309, 3.310 (2020). 2. A bilateral thumb disability was not incurred in service, nor may it be presumed to have been incurred in service. 38 U.S.C. §§ 1101, 1110, 1112, 1113, 1116, 1131, 5103, 5103(A) (2012); 38 C.F.R. §§ 3.303, 3.307, 3.309, 3.310 (2020). 3. A little left finger disability was not incurred in service, nor may it be presumed to have been incurred in service. 38 U.S.C. §§ 1101, 1110, 1112, 1113, 1116, 1131, 5103, 5103(A) (2012); 38 C.F.R. §§ 3.303, 3.307, 3.309, 3.310 (2020). REASONS AND BASES FOR FINDINGS AND CONCLUSIONS The Veteran served in active duty service with the Air Force from July 1969 to March 1973. This matter is on appeal from a March 2011 rating decision. The Veteran was afforded a March 2019 hearing before the undersigned Judge. A transcript of the hearing has been associated with the claims record. The Board remanded this appeal in August 2019 for additional development. The Board notes the issues on appeal in the August 2019 remand were for entitlement to service connection for a lumbar spine disability to include degenerative disc disease as secondary to bilateral knee degenerative joint disease; cervical spine disability to include degenerative disc disease as secondary to bilateral knee degenerative joint disease; bilateral thumb degenerative joint disease as secondary to bilateral knee degenerative joint disease; and left little finger degenerative joint disease as secondary to bilateral knee degenerative joint disease. During the pendency of the appeal, an October 2020 rating decision granted service connection for a lumbar spine disability. Accordingly, this issue is accordingly no longer on appeal. In February 2021, the Board again remanded the remaining issues for additional development. Service Connection Laws and Regulations Service connection will be granted if the evidence demonstrates that a current disability resulted from an injury or disease incurred in or aggravated by active military service. 38 U.S.C. §§ 1110, 1131; 38 C.F.R. § 3.303(a). To establish a right to compensation for a present disability, a Veteran must show: "(1) the existence of a present disability; (2) in-service incurrence or aggravation of a disease or injury; and (3) a causal relationship between the present disability and the disease or injury incurred or aggravated during service." Davidson v. Shinseki, 581 F.3d 1313, 1315-16 (Fed. Cir. 2009); Shedden v. Principi, 381 F.3d 1163, 1167 (Fed. Cir. 2004). Certain diseases, to include arthritis, may be presumed to have been incurred in service when manifest to a compensable degree within one year of discharge from active duty. 38 U.S.C. § 1112 (2012); 38 C.F.R. §§ 3.307, 3.309 (2020). Under 38 C.F.R. § 3.303(b), an alternative method of establishing the second and third Shedden for certain chronic disabilities such as arthritis is through a demonstration of continuity of symptomatology. In relevant part, 38 U.S.C. § 1154(a) requires that the VA give "due consideration" to "all pertinent medical and lay evidence" in evaluating a claim to disability or death benefits. Lay evidence can be competent and sufficient to establish a diagnosis of a condition when (1) a layperson is competent to identify the medical condition, (2) the layperson is reporting a contemporaneous medical diagnosis, or (3) lay testimony describing symptoms at the time supports a later diagnosis by a medical professional." Jandreau v. Nicholson, 492 F.3d 1372, 1377 (Fed.Cir.2007). In fact, competent medical evidence is not necessarily required when the determinative issue involves either medical etiology or a medical diagnosis. Id. at 1376-77; see also Buchanan v. Nicholson, 451 F.3d 1331, 1337 (Fed. Cir. 2006); Davidson v. Shinseki, 581 F.3d 1313 (Fed. Cir. 2009). Once evidence is determined to be competent, the Board must determine whether such evidence is also credible. See Layno, supra (distinguishing between competency ("a legal concept determining whether testimony may be heard and considered") and credibility ("a factual determination going to the probative value of the evidence to be made after the evidence has been admitted"). When there is an approximate balance of positive and negative evidence regarding any issue material to the determination of a matter, the VA shall give the benefit of the doubt to the claimant. 38 U.S.C. § 5107(b). Under 38 C.F.R. § 3.310(a), service connection may be granted for disability that is proximately due to or the result of a service- connected disease or injury. Such permits a grant of service connection not only for disability caused by a service-connected disability, but for the degree of disability resulting from aggravation to a nonservice- connected disability by a service- connected disability. Id. See also Allen v. Brown, 7 Vet. App. 439, 448 (1995); 38 C.F.R. § 3.310(b). In order to prevail on the issue of entitlement to secondary service connection, there must be (1) evidence of a current disability; (2) evidence of a service-connected disability; and (3) nexus evidence establishing a connection between the service-connected disability and the current disability. See Wallin v. West, 11 Vet. App. 509, 512 (1998). Cervical Spine The Veteran's service treatment records, including the February 1973 separation examination, are negative for treatments or complaints related to a cervical spine disability. Notably, the Veteran is currently service connected for bilateral total knee replacement, previously evaluated as bilateral knee chondromalacia with degenerative joint disease. A March 2010 VA treatment report noted that the Veteran presented with neck pain that began 2 months ago. X-rays revealed degenerative joint disease of the cervical spine. The Veteran was afforded a May 2011 VA examination for his knees. The examiner observed the Veteran with abnormal gait and walk due to knee pain and required use of a cane for ambulation. In a submitted February 2012 notice of disagreement (NOD) and at the March 2019 hearing, the Veteran testified that VA doctors told him that his gait has changed due to his knees and this would put pressure on his spine and therefore his lumbar and cervical spine were clearly secondary to his service-connected bilateral knee condition. The Veteran underwent a VA examination for his back and neck in August 2015. The examiner gave diagnoses of lumbosacral strain, cervical strain and degenerative arthritis of the spine. The examiner opined that it was less likely than not that the Veteran's cervical spine disability was proximately due to or the result of the Veteran's service-connected knee disabilities. The examiner noted that there was very little in the medical records regarding a neck disability as the first entry noted was in 2010 which was 35 years after the Veteran's service. His service treatment records were also negative for complaints or treatments of a neck disability. The examiner concluded that there was no connection between a cervical spine disability and the Veteran's longstanding knee disability. In a January 2016 addendum opinion, the VA examiner opined that it was less likely than not that the Veteran's neck disability was proximately due to, the result of, or aggravated by the Veteran's bilateral knee disability. The examiner noted that the Veteran's diagnosed degenerative arthritis of the spine was not a known risk factor associated with the osteoarthritis of the spine, and the lumbosacral and cervical strain were "time-limited conditions that resolve in a few weeks to a few months." The examiner also added that review of the medical record showed the first complaints or medical evidence of lumbar or cervical-related complaints came decades after the Veteran's separation from service. The Veteran underwent a VA examination in November 2019. The examiner opined that it was less likely than not that the Veteran's neck disability was proximately due to or the result of the Veteran's bilateral knee disability. The examiner noted that knee injuries, including those that would cause permanent incapacity or gait disturbances do not routinely cause cervical spine conditions, injuries or separate disabilities. The neck was totally separate from the knee and functioned separately from the knee and as such was not influenced by diseases, disorders, or disabilities of the knees. Regarding the argument of a gait disturbance, the examiner noted that the Veteran had arthritis in both hips and both knees and continued to weight bear on both lower extremities. This did not cause appreciable "high-impact" to the spine. Additionally, the vast number of individuals with knee disabilities are not predisposed toward developing and do not develop independent cervical injuries or disabilities. It was not possible to state that any gait change was due to his knees which would put pressure on the spine and therefore his cervical spine was clearly secondary to his service-connected bilateral knee disability. It was more likely that while in his 70's, the Veteran accumulated degenerative arthritis in multiple joints as the Veteran also had arthritis in multiple joints, including the shoulders, hands and fingers, that would not be affected at all by the asymmetrical walking. The examiner also noted the Veteran's hearing testimony and indicated that it was not clear from the testimony that the Veteran actually would have had asymmetrical walking in a cumulative fashion over time as sometimes he might favor the right and sometimes the left. The examiner also agreed with the January 2016 VA opinion that the cervical strain was a time-limited condition that resolve in a few weeks to a few months and that the degenerative arthritis was not a known causative factor in the development of the arthritis of the spine. In a March 2021 addendum opinion, the November 2019 VA examiner opined that it was less likely than not that the Veteran's neck disability was proximately due to or the result of the Veteran's bilateral knee disability. The examiner again noted that knee injuries, including those that would cause permanent incapacity or gait disturbances do not routinely cause cervical spine conditions, injuries or separate disabilities. The neck was totally separate from the knee and functioned separately from the knee and as such was not influenced by diseases, disorders, or disabilities of the knees. The examiner noted that arthritis in the knees does not "jump around" or spread to other locations and that there was no relationship or interconnectedness to explain such a causal relationship. The examiner noted that even when considering that knee disabilities might produce an abnormal gait or weight-bearing, this would not affect the neck or the cervical spine which was anatomically above those locations and not affected by the wear and tear of the knees. The examiner also opined that it was less likely than not that the Veteran's cervical spine disability was aggravated beyond its natural progression by his service-connected bilateral knee disability. Additionally, there was no evidence that the Veteran's cervical spine disability at its onset during or was otherwise related to his active service duty. While the May 2011 VA examiner observed an abnormal gait and walk due to knee pain, and knee pain can cause one to favor one side or the other with respect to weight-bearing, that would not be likely to affect the cervical spine of the neck or be the proximate cause of arthritis or even muscular strain in that location. The abnormal gait at the knees did not cause one to add additional stresses or weight-bearing to the head or neck bones or joints as the head and neck are above the areas of stress. The examiner concluded that the Veteran's knee disabilities, to include potential for a gait disturbance, did not cause appreciable asymmetrical "high-impact" to the spine. When considering the pertinent evidence of record in light of the above-noted legal authority, the Board finds that service connection for a cervical spine disability is not warranted. As there is arthritis of the cervical spine, the first element of service connection is satisfied. However, a veteran seeking disability benefits must establish not only the existence of a disability, but also an etiological connection between his military service and the disability. Boyer v. West, 210 F.3d 1351, 1353 (Fed. Cir. 2000); D'Amico v. West, 209 F.3d 1322, 1326 (Fed. Cir. 2000); Hibbard v. West, 13 Vet. App. 546, 548 (2000). As noted above, service connection may be granted on a presumptive basis for certain chronic diseases, including arthritis, if such disabilities are shown to be manifest to a degree of 10 percent or more within one year following the Veteran's separation from active military service. See 38 U.S.C. §§ 1101, 1112, 1113; 38 C.F.R. §§ 3.307, 3.309. In this instance however, service connection for a cervical spine disability on a presumptive basis is not warranted as the record does not show evidence of a cervical spine disability within one year of the Veteran's separation from active duty. To the extent that the Veteran is asserting that he experienced continuing symptoms of a cervical spine disability thereafter, the Board acknowledges that a layperson is competent to testify in regard to the onset and continuity of symptomatology. Heuer v. Brown, 7 Vet. App. 379, 384 (1995); Falzone v. Brown, 8 Vet. App. 398, 403 (1995); Caldwell v. Derwinski, 1 Vet. App. 466 (1991). Furthermore, lay witnesses may, in some circumstances, opine on questions of diagnosis and etiology. See Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009) (finding that the Board's categorical statement that "a valid medical opinion" was required to establish nexus, and that a layperson was "not competent" to provide testimony as to nexus because she was a layperson, conflicts with Jandreau). However, as the Veteran was not diagnosed with a cervical spine disability until many years after service and there was a significant period between his service and his post-service complaints where the medical record was silent for complaints of a cervical spine disability, the Board concludes that the weight of the evidence is against a finding of any continuity of symptomatology. See Maxson v. Gober, 230 F.3d 1330, 1333 (Fed. Cir. 2000); Shaw v. Principi, 3 Vet. App. 365 (1992). Regarding service connection on a direct basis, the Board again notes that the Veteran's service treatment records are negative for complaints or treatments of a cervical spine disability and his separation examination was also negative for cervical spine complaints or treatments. Furthermore, the only medical opinions addressing the etiology of the cervical spine disability weigh against the claim. As noted above, the November 2019 VA examiner indicated that it was less likely than not that the Veteran's cervical spine was incurred in or caused by the claimed in-service event, injury or illness. Further, there is no competent evidence or opinion even suggesting that there exists a medical nexus between current cervical spine disability and the Veteran's service and neither the Veteran nor his representative have presented or identified any such existing medical evidence or opinion. The Board finds that the competent evidence of record, while showing the currently diagnosed cervical spine disability, does not demonstrate that the Veteran's cervical spine disability is related to the Veteran's service. Finally, the Veteran is also claiming service connection for a cervical spine disability as secondary to his service-connected bilateral knee disability. As noted above, service connection may be granted for a disability that is proximately due to or the result of an established service-connected disability. 38 C.F.R. § 3.310 (2020). However, the Board finds that the weight of the evidence is against a finding that a current cervical spine disability was related to service or caused or aggravated by a service-connected disability. Again, the only medical opinions addressing the etiology of the cervical spine disability on a secondary basis weigh against the claim as the November 2019 VA examiner indicated that the Veteran's cervical spine disability was less likely than not as due to or aggravated by his service-connected bilateral knee disabilities. Additionally, the November 2019 VA examiner specifically addressed the Veteran's statements about VA doctors telling him that his changed gait would impact his cervical spine as a May 2011 VA knee examination observed that the Veteran had abnormal gait and walk due to knee pain. The examiner in a March 2021 addendum opinion noted that while the May 2011 VA examiner observed an abnormal gait and walk due to knee pain, and knee pain can cause one to favor one side or the other with respect to weight-bearing, that would not be likely to affect the cervical spine of the neck or be the proximate cause of arthritis or even muscular strain in that location. The abnormal gait at the knees did not cause one to add additional stresses or weight-bearing to the head or neck bones or joints as the head and neck are above the areas of stress. The examiner concluded that the Veteran's knee disabilities, to include potential for a gait disturbance, did not cause appreciable asymmetrical "high-impact" to the spine. None of the competent medical evidence currently of record refutes these conclusions, and the Veteran has not presented or identified any such existing medical evidence or opinion. Consequently, entitlement to service connection for a cervical spine disability is not warranted on a direct or secondary basis. In sum, for the reasons and bases expressed above the Board finds that the preponderance of the evidence is against the Veteran's claim of entitlement to service connection. The benefit-of-the-doubt rule does not apply, and the claim must be denied. 38 U.S.C. § 5107(b). Thumbs and Left Little Finger At the Veteran's March 2019 hearing, the Veteran testified that his duties in service involving refueling vehicles required him to attach and remove fueling hoses multiple times a day. The Veteran stated that he did this work five to fifteen times a day all year, resulting in aching hands and fingers. The Veteran also stated that his thumb and left little finger disabilities were related to his service-connected knee disabilities because he described that whenever his knees gave out and caused him to fall, he would need to grab or slam his hand against the wall or a desk to steady himself or break his fall and therefore hurt his hands. The Veteran's service treatment records, including the February 1973 separation examination, are negative for treatments or complaints related to a bilateral thumb or left little finger disability. The Veteran underwent a VA examination in November 2019. The examiner opined that it was less likely than not that the Veteran's bilateral thumb and left little finger disabilities were proximately due to the Veteran's service-connected bilateral knee disability. The examiner noted that there was no connection between the axial skeletal components of the knee and that of the hands and fingers. Arthritis of the knee would have no direct bearing on arthritis of the hands and if arthritis of the hands or fingers were to develop separately, that would be an unrelated or systemic or generalized degenerative condition. Additionally, there was no reference to hand or finger conditions in service and in fact none until after the Veteran was over 65 years of age at which time generalized or degenerative arthritis is quite common. The examiner also considered the possibility of a fall onto the outstretched hands or finger to be a potential for this acquired disability. Notably, in August 2018, the Veteran fell and suffered an injury. However, from that injury it was noted that falls seemed to be out of the ordinary for the Veteran and there was no mention of recurrent falls. No recommendations were made to restrict mobility or to take precautions to avoid such falls because they were not considered recurrent. The injuries were also to the elbow and the shoulder not to the hand or finger. There was no mention of the hand or finger and x-rays of the hands and finger were not performed. Notably, x-rays of the shoulders taken at the time of the falls did not demonstrate arthritis. The examiner noted that if the Veteran had been experiencing recurrent falls producing arthritis in the shoulders, the only way that such impact or force would transfer to the hands and fingers would be if the impact were transferred through the skeletal system, mechanically through the elbows. The absence of arthritis in the elbows at age 72 argued against recurrent falls onto an outstretched hand with a brunt force transferred onto the hands and fingers. The presence of arthritis in the shoulder joint and absence of arthritis in the elbows pointed to an alternative cause such as repetitive use of the shoulder or other conditions that might affect the shoulder without injuring the elbow and distal forearm. The examiner noted that none of the history points toward the knee being the culprit for the fall as the Veteran again had arthritis in the hip. The arthritis that was found was unrelated to the fall and unrelated to the hands and fingers which were not even injured. The examiner also opined that it was less likely than not that the Veteran's bilateral thumb and left little finger disability were aggravated by his service-connected bilateral knee disabilities as there was no direct connection between those elements of the skeletal system and they were located on separate extremities. The examiner noted that even given the Veteran's history and recollection of some falls related to his knees, there was insufficient evidence to opine that that the bilateral knee disability would be the proximate cause of the bilateral thumb and left little finger disabilities. The examiner also opined that it was less likely than not that the Veteran's bilateral thumb and left little finger disabilities had their onset in service or were otherwise related to service. The examiner noted that there were no medical visits related to falls that were sufficient and severe enough to cause pain and no medical visits related to recurrent falls frequent enough to raise concern about stability or balance or independent ambulation. In a March 2021 addendum opinion, the November 2019 VA examiner opined that it was less likely than not that the Veteran's bilateral thumb and left little finger disabilities were proximately due to the Veteran's service-connected bilateral knee disability. The examiner noted that arthritis in the knees does not "jump around" or spread to other locations and that there was no relationship or interconnectedness to explain such a causal relationship. The examiner noted that even when considering that knee disabilities might produce an abnormal gait or weight-bearing, this would not affect the hands, fingers and thumbs which were anatomically above those locations and not affected by the wear and tear of the knees. Knee injuries, including those that would cause permanent incapacity or gait disturbances, do not routinely cause hand and finger conditions, injuries or separate disabilities. The hands and fingers were totally separate from the knees and function separately from the knees and as such are not influenced by disease, disorders or disabilities of the knees. Regarding falls, the examiner noted that a February 2021 treatment report indicated that since the Veteran's most recent knee surgery in 2015, the Veteran had fallen "about once a month". There were falls documented in August 2018 and one in 2019 and another fall but none of these incidents described injuries to the hands or thumbs. The injuries reported were to the elbows and shoulders. The examiner also opined that it was less likely than not that the Veteran's thumb and finger disabilities were aggravated by his service-connected bilateral knee disability. The examiner noted that one would rarely fall and catch themselves with their thumbs and 5th digit while sparing the other fingers. Even given the Veteran's history of some falls related to his knees, there was insufficient evidence to opine that the knee disability would be the proximate cause of the thumb and finger disabilities. It was also noted that the natural progression of arthritis would be gradual worsening with time and the effects of age-related degenerative changes of the bones. The baseline of the Veteran's thumb and fingers were considered to be what was present at discharge from service but there was no evidence that the knee disability in any way aggravated or worsened the hand, finger or bilateral thumb conditions beyond that which was attributed to other causes or the natural progression of diseases such as degenerative arthritis. Additionally, there was no evidence that the Veteran's hand, finger or bilateral thumb conditions had their onset during or were otherwise related to his active service duty as the examiner noted that there were no references to hand, finger or bilateral thumb disabilities in service and none until the Veteran was 65 years old at which time generalized arthritis or degenerative arthritis is quite common. Regarding the Veteran's March 2019 testimony regarding his duties in active duty service handling fuel hoses multiple times a day resulting in pain in his hands, and statements that he hurt his hands from falls when his knees give out, the examiner noted that "handling fuel hoses multiple times a day" would be considered normal wear and tear for most people in the industrial or construction occupational fields. The Veteran was also transferred away from this role as he had an "allergy to fuel". The fact that the Veteran had no registered complaints of hand, finger or thumb disabilities during service and had no medical visits related to his hand, finger or thumb until he was over 65 made it unlikely that any acute strain, chronic injury or even repetitive motion injuries resulted from cumulative trauma because they would present with pain and symptoms at the time or immediately after repetitive use rather than with a delayed effect many years later. At age 65 and after many years of non-service related use, generalized or degenerative arthritis was quite common and became the greater likelihood. The examiner again noted that even given the Veteran's history of some falls related to his knees, there was insufficient evidence to opine that the knee disability would be the proximate cause of the bilateral thumb and left finger disabilities. The examiner indicated that even if the Veteran's testimony was considered true and accurate, there was no support of a mechanism of injury that would substantiate causation or create a nexus. When considering the pertinent evidence of record in light of the above-noted legal authority, the Board finds that service connection for bilateral thumb and little left finger disabilities is not warranted. At the Veteran's November 2019 VA examination, it was noted that the Veteran had bilateral thumb and little left finger pain. The Board notes that the current disability definition for VA compensation purposes is broad and includes functional impairment due to pain. Saunders v. Wilkie, 886 F. 3d 1356, 1367-68 (2018). As there are current bilateral thumb and little left finger disabilities, the first element of service connection is satisfied. However, a veteran seeking disability benefits must establish not only the existence of a disability, but also an etiological connection between his military service and the disability. Boyer v. West, 210 F.3d 1351, 1353 (Fed. Cir. 2000); D'Amico v. West, 209 F.3d 1322, 1326 (Fed. Cir. 2000); Hibbard v. West, 13 Vet. App. 546, 548 (2000). As noted above, service connection may be granted on a presumptive basis for certain chronic diseases, including arthritis, if such disabilities are shown to be manifest to a degree of 10 percent or more within one year following the Veteran's separation from active military service. See 38 U.S.C. §§ 1101, 1112, 1113; 38 C.F.R. §§ 3.307, 3.309. In this instance, there is some question as to whether the Veteran has a current diagnosis of arthritis of the bilateral thumb and little left finger. Regardless, service connection for arthritis on a presumptive basis is not warranted as the record does not show evidence of arthritis within one year of the Veteran's separation from active duty. To the extent that the Veteran is asserting that he experienced continuing symptoms of bilateral thumb and little left finger disabilities thereafter, the Board acknowledges that a layperson is competent to testify in regard to the onset and continuity of symptomatology. Heuer v. Brown, 7 Vet. App. 379, 384 (1995); Falzone v. Brown, 8 Vet. App. 398, 403 (1995); Caldwell v. Derwinski, 1 Vet. App. 466 (1991). Furthermore, lay witnesses may, in some circumstances, opine on questions of diagnosis and etiology. See Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009) (finding that the Board's categorical statement that "a valid medical opinion" was required to establish nexus, and that a layperson was "not competent" to provide testimony as to nexus because she was a layperson, conflicts with Jandreau). However, as the Veteran was not diagnosed with bilateral thumb and little left finger disabilities until many years after service and there was a significant period between his service and his post-service complaints where the medical record was silent for complaints of bilateral thumb and little left finger disabilities, the Board concludes that the weight of the evidence is against a finding of any continuity of symptomatology. See Maxson v. Gober, 230 F.3d 1330, 1333 (Fed. Cir. 2000); Shaw v. Principi, 3 Vet. App. 365 (1992). Regarding service connection on a direct basis, the Board again notes that the Veteran's service treatment records are negative for complaints or treatments of bilateral thumb and little left finger disabilities and his separation examination was also negative for bilateral thumb and little left finger disabilities complaints or treatments. Furthermore, the only medical opinions addressing the etiology of the bilateral thumb and little left finger disabilities weigh against the claim. As noted above, the November 2019 VA examiner in a November 2019 VA examination report and March 2021 addendum opinion indicated that it was less likely than not that the Veteran's bilateral thumb and little left finger disabilities were incurred in or caused by the claimed in-service event, injury or illness. Notably, the examiner specifically addressed the Veteran's contentions regarding his duties in active duty service handling fuel hoses multiple times a day resulting in pain in his hands as the examiner in the March 2021 addendum opinion noted that the fact that the Veteran had no registered complaints of hand, finger or thumb disabilities during service and had no medical visits related to his hand, finger or thumb until he was over 65 made it unlikely that any acute strain, chronic injury or even repetitive motion injuries resulted from cumulative trauma because they would present with pain and symptoms at the time or immediately after repetitive use rather than with a delayed effect many years later Further, there is no competent evidence or opinion even suggesting that there exists a medical nexus between current bilateral thumb and little left finger disabilities n and the Veteran's service and neither the Veteran nor his representative have presented or identified any such existing medical evidence or opinion. The Board finds that the competent evidence of record, while showing the currently diagnosed bilateral thumb and little left finger disabilities, does not demonstrate that the Veteran's bilateral thumb and little left finger disabilities are related to the Veteran's service. Finally, the Veteran is also claiming service connection for bilateral thumb and little left finger disabilities as secondary to his service-connected bilateral knee disabilities. As noted above, service connection may be granted for a disability that is proximately due to or the result of an established service-connected disability. 38 C.F.R. § 3.310 (2020). However, the Board finds that the weight of the evidence is against a finding that current bilateral thumb and little left finger disabilities were related to service or caused or aggravated by a service-connected disability. Again, the only medical opinions addressing the etiology of the bilateral thumb and little left finger disabilities on a secondary basis weigh against the claim as the November 2019 VA examiner indicated that the Veteran's bilateral thumb and little left finger disabilities were less likely than not as due to or aggravated by his service-connected bilateral knee disabilities. Notably, the November 2019 VA examiner specifically addressed the Veteran's contentions regarding him hurting his hands from falls when his knees gave out. The examiner noted that one would rarely fall and catch themselves with their thumbs and 5th digit while sparing the other fingers. The examiner also noted that even given the Veteran's history of some falls related to his knees, there was insufficient evidence to opine that the knee disability would be the proximate cause of the thumb and finger disabilities as it was noted that the natural progression of arthritis would be gradual worsening with time and the effects of age-related degenerative changes of the bones. The baseline of the Veteran's thumb and fingers were considered to be what was present at discharge from service but there was no evidence that the knee disability in any way aggravated or worsened the hand, finger or bilateral thumb conditions beyond that which was attributed to other causes or the natural progression of diseases such as degenerative arthritis. None of the competent medical evidence currently of record refutes these conclusions, and the Veteran has not presented or identified any such existing medical evidence or opinion. Consequently, entitlement to service connection for bilateral thumb and little left finger disabilities are not warranted on a direct or secondary basis. In sum, for the reasons and bases expressed above the Board finds that the preponderance of the evidence is against the Veteran's claims of entitlement to service connection. The benefit-of-the-doubt rule does not apply, and the claims must be denied. 38 U.S.C. § 5107(b). All Disabilities The Board notes the Veteran's contentions regarding the etiology of his claimed cervical spine, bilateral thumb and little left finger disabilities. To the extent that the Veteran himself contends that a medical relationship exists between his claimed current cervical spine, bilateral thumb and little left finger disabilities and service, the Board acknowledges that the Veteran is competent to testify as to his observations. Jandreau v. Nicholson, 492 F.3d 1372, 1376-77 (Fed. Cir. 2007). Furthermore, lay witnesses may, in some circumstances, opine on questions of diagnosis and etiology. See Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009) (finding that the Board's categorical statement that "a valid medical opinion" was required to establish nexus, and that a layperson was "not competent" to provide testimony as to nexus because she was a layperson, conflicts with Jandreau). In the instant case, however, the Board finds that cervical spine, bilateral thumb and little left finger disabilities are not disabilities subject to lay diagnosis as these diagnoses require medical training. More significantly, the Veteran and his representative do not have the medical expertise to provide an opinion regarding the claimed cervical spine, bilateral thumb and little left finger disabilities etiologies. Specifically, where the determinative issue is one of medical causation, only those with specialized medical knowledge, training, or experience are competent to provide evidence on the issue. See Jones v. West, 12 Vet. App. 460, 465 (1999). Additionally, the VA examiner provided detailed rationale in support of his opinions and cited to the relevant evidence. For this reason, the VA examiner's opinions are the most probative evidence of record. See Prejean v. West, 13 Vet. App. 444, 448-9 (2000) (noting that a factor for assessing the probative value of a medical opinion includes the thoroughness and detail of the opinion). In sum, for the reasons and bases expressed above the Board finds that the preponderance of the evidence is against the Veteran's claims of entitlement to service connection for cervical spine, bilateral thumb and little left finger disabilities. The benefit-of-the-doubt rule does not apply, and the claims must be denied. 38 U.S.C. § 5107(b). MICHAEL LANE Veterans Law Judge Board of Veterans' Appeals Attorney for the Board James A. DeFrank, Counsel The Board's decision in this case is binding only with respect to the instant matter decided. This decision is not precedential and does not establish VA policies or interpretations of general applicability. 38 C.F.R. § 20.1303.