Yes. An aggravation of a pre-existing condition is a compensable injury in Pennsylvania Workers Compensation. You will need medical evidence to establish that your prior injury/condition worsened as a result of the work place injury/incident/activity. This also applies, of course, to other body parts and injuries.
Inevitably, the employer and work comp insurer will try to assert that there is no work injury and that the condition you have is merely the old problem, recurring. The longer it has been since you treated for the prior issues, the greater the chances of proving a work injury- in most cases. A careful review of the medical records will be necessary by your work comp lawyer.
For a complete analysis, call Michael W. Cardamone- Experienced PA Work Comp Lawyer at 215-206-9068 or email him at Michael@cardamonelaw.com for a prompt reply.