38 CFR 3.310(b): Documenting Secondary Service Connection for Contralateral Knee DJD

Direct answer

Under 38 C.F.R. § 3.310(b), a secondary service connection claim for degenerative joint disease (DJD) of the contralateral knee based on aggravation of a nonservice-connected condition by a service-connected orthopedic condition requires three categories of medical evidence:

1. Baseline severity evidence — medical evidence establishing the baseline level of severity of the nonservice-connected DJD, created either before the onset of aggravation or as the earliest medical evidence created between the onset of aggravation and the evidence establishing the current level of severity [1].
2. Current severity evidence — medical evidence establishing the current level of severity of the DJD [1].
3. Nexus evidence — medical evidence establishing that any increase in severity of the contralateral knee DJD is "proximately due to or the result of" the service-connected orthopedic condition "and not due to the natural progress of the nonservice-connected disease" [1].

Analysis

The statutory framework of § 3.310(b)

Section 3.310(b) governs aggravation of a nonservice-connected disability by a service-connected disability. The regulation provides:

> "Any increase in severity of a nonservice-connected disease or injury that is proximately due to or the result of a service-connected disease or injury, and not due to the natural progress of the nonservice-connected disease, will be service connected." [1]

The regulation then imposes a critical evidentiary gatekeeping requirement:

> "VA will not concede that a nonservice-connected disease or injury was aggravated by a service-connected disease or injury unless the baseline level of severity of the nonservice-connected disease or injury is established by medical evidence created before the onset of aggravation or by the earliest medical evidence created at any time between the onset of aggravation and the receipt of medical evidence establishing the current level of severity of the nonservice-connected disease or injury." [1]

This means that without medical evidence documenting the baseline severity of the contralateral knee DJD, VA will not even concede that aggravation occurred. The burden falls on the claimant to produce (or have in the record) medical evidence that fixes a baseline level of disability for the nonservice-connected knee condition.

How the rating activity calculates aggravation

Once both baseline and current severity levels are established, the regulation prescribes a specific methodology:

> "The rating activity will determine the baseline and current levels of severity under the Schedule for Rating Disabilities (38 CFR part 4) and determine the extent of aggravation by deducting the baseline level of severity, as well as any increase in severity due to the natural progress of the disease, from the current level." [1]

Thus, the rating activity must:

• Assign a diagnostic-code-based evaluation under 38 C.F.R. Part 4 to the baseline level of the contralateral knee DJD [1].
• Assign a diagnostic-code-based evaluation to the current level of the same condition [1].
• Subtract the baseline rating and any portion of the increase attributable to natural progression from the current rating, leaving only the aggravation attributable to the service-connected orthopedic condition [1].

Application to the contralateral knee scenario

For a claim that a service-connected orthopedic condition (e.g., a service-connected knee or hip condition) has aggravated DJD of the contralateral knee, the required documentation includes:

1. Medical records establishing baseline severity. These must be medical records — competent medical evidence from a qualified provider — that document the status of the contralateral knee DJD before the aggravation began, or the earliest available medical evidence from the period between the onset of aggravation and the current evaluation [1]. Competent medical evidence is defined as "evidence provided by a person who is qualified through education, training, or experience to offer medical diagnoses, statements, or opinions" [17].

2. Medical records establishing current severity. Current examination findings, imaging, and clinical assessment of the contralateral knee, sufficient to assign a rating under 38 C.F.R. Part 4 [1].

3. A medical nexus opinion. The evidence must establish that the increase in severity is "proximately due to or the result of" the service-connected orthopedic condition — for example, through altered gait mechanics, overloading of the contralateral knee, or biomechanical compensation — and "not due to the natural progress" of the DJD [1]. The nexus opinion must address both causation and the absence of natural progression as the sole cause.

Distinction from § 3.310(a)

If the claim theory is that the contralateral knee DJD was caused by (not merely aggravated by) the service-connected orthopedic condition, the claim may proceed under § 3.310(a), which provides that "[d]isability which is proximately due to or the result of a service-connected disease or injury shall be service connected" [1]. Under this pathway, the baseline-severity documentation requirement of § 3.310(b) does not apply; the claimant instead must establish proximate causation through a nexus opinion [1]. The choice between subsections (a) and (b) depends on whether the contralateral knee DJD is framed as a new condition caused by the service-connected disability or as a preexisting condition worsened beyond its natural course [1].

Key points

• Baseline documentation is mandatory under § 3.310(b). Without medical evidence establishing the baseline level of severity of the nonservice-connected DJD, VA "will not concede" aggravation [1].
• The baseline evidence must be medical evidence — created either before the onset of aggravation or as the earliest evidence between the onset of aggravation and the current severity evidence [1].
• Two deductions are required from the current rating: the baseline level of severity and any increase due to natural progression of the DJD are both subtracted, leaving only the aggravation attributable to the service-connected condition [1].
• The nexus must address natural progression. The medical evidence must demonstrate that the worsening is proximately due to the service-connected orthopedic condition and exclude natural progression of the DJD as the cause [1].
• If causation rather than aggravation is the theory, § 3.310(a) may apply instead, which does not impose the baseline-documentation requirement but still requires competent medical evidence of proximate causation [1].