As we know, it’s virtually impossible to prove apportionment to pre-existing arthritis/degenerative conditions without proof that the prior condition was “disabling in a compensation sense”. That’s often impossible because most claimants have either been living with it without treatment, or they’ve treated with their primary care doctor and don’t disclose it because it wasn’t the result of an “injury”. And unless we know the treatment records are out there, you’re stuck.