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Background The variation of the anterolateral ligament (ALL) length during knee motion is still unclear, and the knee position in which a reconstruction graft should be tensioned remains controversial. The objective of this study was to determine the variation of the ALL length during knee motion using a three-dimensional optoelectronic system. Methods Kinematic analyses of 20 cadaveric knees were performed using a Motion Analysis® system. The variability of the measurements made during the five acquisition cycles was studied. Reliability was evaluated by two separate measurement sessions, with complete system reinstallation, using different cadavers and a new operator. The ALL length was analysed from extension to full flexion in three rotational conditions. Findings When analysing the reliability of the five cycles, 82% of the measurements we found to have an Intra Class Correlation (ICC) >0.85. The reproducibility of inter-sessional measures by different operators and different cadavers was either good (ICC >0.75) or excellent (ICC >0.85). The ALL length was maximum in full internal rotation with the knee at 25° of flexion. Interpretation This three-dimensional optoelectronic protocol allowed us to analyse the variation of the ALL length during intact knee motion with good reliability and the required accuracy to analyse this variable. The maximal length and highest tension of the ALL was reported at 25° of knee flexion in internal rotation, suggesting this as the optimal position for the knee joint when tensioning an ALL reconstruction.

Microfracture (MFx) is a widely used technique in the treatment of articular cartilage defects of the knee. The objective of this study was to determine the prognostic factors of functional outcomes after MFx treatment of knee cartilage defects ≤ 4 cm2.Forty-eight patients who were to be treated by MFx for knee cartilage defects ≤ 4 cm2 were prospectively included. The mean follow-up was 5.7 years (3.7-9.5). Demographics, sport practiced, time from diagnosis to surgery and associated lesions were collected. The cartilage defect was graded according to the ICRS classification. The MOCART score was calculated from a one-year MRI. The subjective VAS and IKDC scores were collected preoperatively and at the latest follow-up. Prognostic factors were determined using univariate and multivariate regression analyses incorporating pre-, peri- and postoperative clinical and radiological criteria. The dependent variable was defined as the difference between the pre- and post-operative clinical scores (dIKDC and dVAS).The mean size of the cartilage defect was 1.8 cm2 (0.8-4). At the last follow-up, the VAS and IKDC scores were significantly improved compared to the pre-operative period (p0.01). The average MOCART score on the one-year MRI was 50 (20-70). Three patients (6 %) who demonstrated filling defects on MRI and debilitating pain required surgical re-intervention. The factors that impacted the functional outcome as reflected by the VAS and IKDC scores were age, BMI, time from diagnosis to surgery, size of the lesion and the MOCART score.This study demonstrates that MFx is a successful first-line treatment option for small articular cartilage defects (≤ 4 cm2) of the knee and provides good function and pain relief in the mid-term. The predictors of poor functional outcomes were older age, higher BMI, longer time from diagnosis to surgery, larger lesion size and lower MOCART score.