Open versus closed kinetic chain exercise: Issues in rehabilitation after anterior cruciate ligament reconstructive surgery

What has been called "closed kinetic chain" (CKC) exercise has become popular in the last 5 to 10 years for use after anterior cruciate ligament (ACL) reconstructive surgery. Closed kinetic chain exercises appear to have gained popularity over more traditionally used open kinetic chain (OKC) exercises because many clinicians believe that CKC exercises are safer and more functional. These clinicians also contend that CKC exercise is equally effective as OKC exercise in restoring quadriceps femoris muscle force production following ACL reconstructive surgery. The purpose of this clinical perspective is to examine the evidence concerning OKC and CKC training after ACL reconstructive surgery with regard to these issues and discuss how physical therapists can best apply this knowledge in clinical practice. Based on the review of data, it does not appear that clinicians should completely abandon more traditional OKC exercises and replace them with CKC exercises in postoperative ACL reconstruction rehabilitation programs. Both types of exercise apparently can be modified to minimize (I) the risk of applying excessive strain on the ACL graft and (2) the risk of excessive patellofemoral joint stress. Depending on the functional goals of the patient, both OKC and CKC exercises may be appropriate for simulating functional activities. When improvement in quadriceps femoris muscle function is an essential treatment goal, therapists may need to combine OKC exercises with CKC exercises to provide optimal training stimuli. Suggestions for further research are discussed.