Temporary pain in the front of the knee is common following ACL reconstruction. This can occur in up to 20 out of 100 patients, and is usually related to the type of graft used. However, over time, with physical therapy and activity modification, this pain normally improves. Permanent pain is rare and is usually associated with a lack of full extension in the knee. It may also be due to pre-existing damage to cartilage that occurred at the time of the injury or from arthritis.