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Purpose The alignment goal in total knee arthroplasty (TKA) remains debated. Two major strategies have emerged based on recreating the native knee: kinematic and functional alignment (KA and FA). Recently a new Coronal Plane Alignment of the Knee (CPAK) classiication for KA, based on bony landmarks, was described considering joint line obliquity and the arithmetic HipKneeAnkle angle (aHKA). Valgus corrected HKA medial angle (vcHKA) was measured on distractive valgus preoperative radiographs compensating for cartilage wear and ligament balance in varus osteoarthritis. The purpose of this study was to determine if aHKA accounts for diferences in medial laxity for the extension gap by comparing vcHKA to aHKA. The hypothesis was that no signiicant diference would be observed between the two measurements. Methods This is a retrospective analysis of 749 knees in consecutive patients presenting to a single-centre with primary medial osteoarthritis. Patients underwent standardized weight bearing long-leg and valgus stress radiographs. Tibial mechanical angle (TMA), femoral mechanical angle (FMA) and vcHKA were measured using digital software. aHKA and vcHKA were compared to determine diferences due to soft tissue balancing. ResultsThe mean FMA was 91.3 ± 2.2° (range 82°-97°), the mean TMA was 85.7 ± 2.5° (range 75°-98°), the mean aHKA was 177.0 ± 3.0° (range 164°-185°) and the mean vcHKA was 176.6 ± 3.1° (range 165°-192°). No signiicant diference was observed between aHKA and vcHKA (p = 0.06). A signiicant correlation was found between vcHKA and TMA (ρ = 0.3; p < 0.001) and between vcHKA and FMA (ρ = 0.41; p < 0.001). Conclusion This study showed that vcHKA was similar to aHKA conirming that aHKA accounts for ligamentous medial laxity. Therefore, kinematic alignment based on the CPAK classiication matches the pre-arthritic coronal alignment of the knee for the extension gap. Level of evidence IV.

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PurposeRecurrent patellar dislocation is a frequent knee disorders in young, active patients. Medial patellofemoral ligament reconstruction (MPFLR) can restore knee stability and function, but the rate of return to sports is less clear. The aim of this study was to evaluate rate of return to sport following treatment of recurrent patellar dislocation with isolated MPFLR. MethodsBetween 2011 and 2018, 113 patients with recurrent patellar dislocation were treated with isolated MPFLR at an academic center. Pre‐injury sports participation and Tegner score, pre‐operative subjective IKDC score, time to return to sports, and post‐operative Tegner and subjective IKDC scores were collected, with a minimum of follow‐up of 2 years. ResultsOne hundred and three patients (91%) were evaluated at a mean of 4.5 ± 2.5‐year post‐operative. 92 patients (89%) participated in sports prior to onset of patellar instability. At final follow‐up, 84 of these 92 patients (91%) were able to return to sports. The mean time from surgery to return to sports was 10.4 ± 8.6 months (range: 2–48 months). 62 patients (67%) returned to the same (50 patients) or higher (12 patients) level. 22 patients (26%) returned at a lower level. 19 of these patients attributed this decreased participation to ongoing knee problems. The median Tegner score was noted to decrease from 5 pre‐injury to 4 post‐operatively (p = 0.02). ConclusionIsolated MPFL reconstruction allowed return to pre‐injury sports in 91% of patients, with 67% of patients returning to the same or higher level than pre‐injury. Mean time to return to sports was 10 months and post‐operative Tegner score was noted to be modestly decreased from pre‐injury level. Level of evidenceIV.