Closed Kinetic Chain Exercises in ACL Rehabilitation: A Systematic Review of Muscle Strength and Functional Outcomes

Abstract

Background

Anterior cruciate ligament (ACL) reconstruction is commonly performed to restore knee stability; however, many patients experience persistent deficits in muscle strength and functional performance, highlighting the importance of effective rehabilitation strategies. Closed kinetic chain (CKC) exercises are widely applied due to their biomechanical advantages in promoting joint stability and neuromuscular control, yet their effectiveness remains variably reported.

Objectives

This study aimed to systematically review and synthesize the effects of CKC exercises on muscle strength and functional outcomes following ACL reconstruction.

Methods

A systematic review design was employed using a structured search across major electronic databases for studies published between 2022 and 2026. Eligibility criteria included studies involving ACL reconstruction patients undergoing CKC-based rehabilitation with reported outcomes on muscle strength and/or functional performance. A total of six studies meeting the inclusion criteria were analyzed. Data were extracted and synthesized using a narrative approach, focusing on key outcome domains including muscle strength, functional performance, and graft stability.

Results

The findings indicate that CKC exercises contribute significantly to improvements in muscle strength, joint stability, and functional performance. Greater strength gains were observed when CKC was combined with other exercise modalities, while CKC alone demonstrated consistent safety in maintaining graft integrity. Functional outcomes improved, although some deficits persisted, influenced by neuromuscular and psychological factors

Conclusion

CKC exercises represent an essential component of ACL rehabilitation, with optimal outcomes achieved through integrated, individualized approaches. This study provides theoretical and practical insights for developing evidence-based rehabilitation protocols, although further high-quality research is needed to establish standardized guidelines.