Service-connection is a really important concept for Military Disability. Both DoD Disability and VA Disability require all medical conditions to be service-connected in order to qualify for disability compensation.
Service-connection means that a condition is related to or directly caused by military service. The exact rules to determine this are different for the Reserves than for Active Duty.
For Active Duty, a condition is considered service-connected if it occurred or was first diagnosed any time while on active duty. It does not have to have occurred while actually performing your job requirements.
For example, Joe served on active duty from 2008 to 2012. In 2009, he was deployed to Iraq and developed hearing loss from exposure to explosions. In 2010, after returning from Iraq, he broke his ankle in a basketball game with some of his civilian friends on the weekend. Since Joe was on active duty, BOTH conditions are considered service-connected, even though one was not a direct result of performing his duties. As long as it occurs or was diagnosed while in the military, it’s service-connected and eligible for benefits.
For Reserves, a condition is considered service-connected only if it occurred while actively participating in military service. This is referred to as Line of Duty (LOD). The Reservist’s commander is the one who determines if a condition occurred while in the Line of Duty. As long as the commander correctly submits a Line of Duty determination form, the condition will be eligible for disability benefits.
So, if Joe was a Reservist instead of active duty, his hearing loss would be eligible for disability, but his broken ankle would not.
Now, the VA will give VA Disability Benefits for conditions that develop after a disabled American veteran leaves the military as long as it can be proven that the condition itself is service-connected, is on the VA Presumptive List, or that it was caused by another condition that is service-connected.
For example, if active-duty-Joe’s ankle condition never fully heals and causes knee pain a few years after he leaves the military, the VA will consider his knee pain as service-connected since it is definitely caused by a service-connected condition. It will be eligible for VA Disability.
Similarly, if Joe starts developing PTSD symptoms years after he leaves the military (a very normal occurrence), the VA will consider it service-connected since he clearly experienced traumatic events while deployed to Iraq (this will have to be proved). So even though it didn’t show up until much later, it is still service-connected.
If, however, Joe develops a skin condition on his ear after he leaves the military, the VA won’t consider it service-connected since there is no medical proof that links skin conditions to hearing loss. Definitely not service-connected.
So, service-connection must be proven for every condition in order for it to be eligible to receive disability compensation. No exceptions.