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An understanding of knee ligament anatomy and biomechanics is foundational for physicians treating knee injuries, especially the more rare and morbid multiligamentous knee injuries. This chapter examines the roles that the cruciate and collateral anatomy and morphology play in their kinematics. Additionally, the biomechanics of the ACL, PCL, MCL, and LCL are discussed as they have surgical and reconstructive implications.

Background: Hip arthroscopy has been shown to be effective in athletes who have femoral acetabular impingement and labral tearing. The effect of complete capsular closure versus nonclosure on return to play is unknown. Hypothesis: Complete capsular closure after hip arthroscopy would lead to a higher rate and faster return to sports in high-level athletes. Study Design: Cohort study; Level of evidence, 3. Methods: A nonrandomized retrospective review was performed of high school, collegiate, and professional athletes undergoing hip arthroscopy by a single high-volume hip arthroscopic surgeon. Athletes were divided into those undergoing complete capsular closure (CC group) and non–capsular closure (NC group) after hip arthroscopy. Rate and time to return to play were determined between the 2 groups. Patient-reported outcomes including modified Harris Hip Score (mHHS), Hip Outcome Score Activities of Daily Living (HOS-ADL), and Hip Outcome Score Sport-Specific Subscale (HOS-SSS) were obtained at a minimum of 2 years. Results: A total of 111 athletes with a minimum 2-year follow-up were included in the study. There were 62 in the CC group and 49 in the NC group. A higher percentage of athletes in the CC group returned to play compared with that in the NC group (90.3% vs 75.5%, respectively; P = .03). The CC group returned to play at a mean ± SD of 4.7 ± 1.9 months compared with 5.8 ± 2.6 months in the NC group ( P < .001). Patients in the CC group met the minimal clinically important difference for the mHHS, HOS-ADL, and HOS-SSS patient-reported outcomes at higher percentages: mHHS, 98.3% vs 87.7% for CC vs NC, respectively ( P = .02); HOS-ADL, 98.3% vs 87.7% ( P = .02); and HOS-SSS, 96.7% vs 89.7% ( P = .13). The difference between groups was statistically significant for mHHS and HOS-ADL. Conclusion: Complete capsular closure after hip arthroscopy was associated with faster return to play and a higher rate of return compared with that of nonclosure of the capsule in this sample population of high-level athletes. At a minimum 2-year follow-up, complete capsular closure was associated with significantly higher patient-reported outcomes compared with those of nonclosure in athletes who underwent hip arthroscopy.