According to the American Academy of Orthopaedic Surgeons (AAOS) (2003), there are four basic kinds of

knee braces:

Functional braces, which are designed to (a) provide stability for the anterior-cruciate ligament (ACL) or

1.  

2. Prophylactic braces, which are designed to prevent or reduce the severity of knee injury
3. Rehabilitative braces, which are designed to allow protected motion of injured knees or knees that have
   Unloader/offloader braces, which are designed to provide pain relief in arthritic knees