Relationship between knee alignment and quadriceps muscle passive tension in individuals with knee osteoarthritis

Abstract

Purpose: Quadriceps is affected in individuals with knee osteoarthritis (KOA) with significant morphology change and dysfunction. The alignment of knee joint could influence properties of quadriceps muscle. Except for strength, feature of quadriceps muscle properties is yet to be investigated in these patients, including muscle passive tension. Knowing the underlying relationship between quadriceps passive tension and malalignment could be important to provide potential treatment strategy targeting on quadriceps dysfunction in KOA. We assumed that knee alignment changed the passive tension of different superficial heads of quadriceps. Methods: KOA patients were recruited from a local hospital from Mar 2017 to Aug 2018. The diagnosis was made by experienced orthopedic doctor through clinical examination and radiography. Patients were included if they have KL grade between 1 and 3, severer OA in the medial tibiofemoral compartment, and knee pain during walking in most of days in the past month. Knee alignment was measured by the EOS bi-planar x-ray imaging system (EOS imaging, Paris, France) in standing position. Knee varus angle, tibiofemoral rotation and tibial torsion were estimated with sterEOS 1.6 software. Supersonic shearwave elastograph (Supersonic Imaging, Aix-en-Provence, France) was used to measure passive muscle tension of superficial heads of quadriceps femoris, including vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VMO). During ultrasound measurement, patients kept relaxed in supine position with knee flexion to 60 degree. SPSS 34.0 was used to make regression curve estimation. Results: 61 patients were eligible for analysis (age: 62.48 ± 5.80 years; gender: female 46/ male 15; BMI: 26.11 ± 3.72 kg/m 2 ), among whom 7 were KL grade 1, 32 were KL grade 2 and 22 were KL grade 3. The result showed that knee varus/valgus alignment was not a significant predictor to either passive tension of VL or RF, while it was significant to that of VMO. It suggested that a good fit of an exponential regression model could be revealed relationship between knee varus angle and VMO passive tension (R 2 ¼0.07, F¼4.04, p<0.05). No significant result could be found between tibiofemoral rotation, tibial torsion and quadriceps passive tension. Conclusions: Our assumption that knee alignment affected passive tension of quadriceps was partly supported. Knee alignment in the frontal plane was strong predictor to passive tension of VMO. The fit of exponential pattern agreed with classical estimation of passive lengthtension curve of skeletal muscles. It indicated that knee varus alignment could influence passive tension of VMO possibly by changing the initial length of the muscle. VMO was the primary dynamic stabilizer of knee joint. Any alteration of muscle property could affect the function of this muscle head. Interpretation of the result should be carefully since the effect seemed minimal. Further study could investigate the relationship between passive tension and knee joint function to explore the therape...