Outside‐In Medial Collateral Ligament Release Shows Superior Evidence for Safe Medial Joint Space Widening and Functional Recovery in Knee Arthroscopy: A Systematic Review
Hesan Rezaee, Mohammad Ayati Firoozabadi, Omid Salkhori, Mahdi Sahebi, Seyed Mohammad Javad MortazaviPurpose
To compare various medial collateral ligament (MCL) release techniques used during knee arthroscopy by evaluating their anatomical targets, biomechanical effects, medial joint space widening, clinical and functional outcomes, and associated complications.
Methods
A comprehensive literature search was performed in PubMed, Scopus, and Web of Science for studies published between January 2000 and June 2025. Eligible studies focused on MCL release in adult knee arthroscopy patients and reported clinical and functional outcomes. Data on medial joint space opening, knee instability, functional scores, and complications were extracted.
Results
Thirteen studies were included, with the outside‐in technique, especially the percutaneous pie‐crusting method, being the most extensively studied. The outside‐in technique consistently achieved the greatest joint space widening, with increases ranging from 2.5 to 12 mm. The inside‐out technique showed moderate joint space expansion (3‐7 mm). Functional outcomes improved significantly across all techniques. The outside‐in technique reported a Lysholm score increase from 48.2 to 80, a visual analog scale score decrease from 5.6 to 1.8, and an International Knee Documentation Committee score rise from 51.4 to 82.2. The inside‐out technique showed a moderate improvement in Lysholm score from 59.3 to 85.7, with no significant differences in instability or long‐term complications. Subperiosteal release also enhanced Lysholm scores from 50 to 92.5, with minor increases in joint laxity that resolved over time. All techniques showed low complication rates, with transient needle tract pain and mild ecchymosis being the most common side effects.
Conclusions
MCL release techniques, especially the outside‐in percutaneous pie‐crusting method, improve medial joint space visualization and medial joint space during knee arthroscopy, aiding meniscal repair, partial meniscectomy, meniscal root repair, and other procedures. These techniques are generally safe but cause temporary ligamentous laxity similar to a grade I MCL sprain, so they are not entirely “benign.” Surgeons must weigh inducing controlled trauma against potential drawbacks of a tighter joint because the risk‐benefit balance varies case by case.
Level of Evidence
Level IV, systematic review of Level III and IV studies.