That's sad. I hope the officer makes a full recovery.
Do you have a light-duty policy? I've seen positive examples in public safety and public works. A knee injury may prevent field work for several months, but that person can remain at work in a defined light-duty role, working on reports, grants, or IT, or training and mentoring junior staff. We had a very positive example of this at a wastewater plant. With HR helping to define the light-duty scope of work and the conditions of return, your officer could offer much in terms of community policing, advising or training, or community outreach.
Do you have a volunteer reserve unit? Many localities keep corps of police volunteers for support --parking patrol, crowd control, youth events, light office work. The volunteers may be young aspiring officers, retirees, or boosters. The danger to the injured officer's shift could motivate volunteers to step up and help where permissible, freeing patrol officers to focus on patrol. Again, the injured officer could act in a light-duty capacity as a volunteer coordinator to recruit, motivate, and train several unpaid auxiliaries.