Knee osteoarthritis (KOA) is the most common chronic bone joint disease. The WHO points out that KOA has become the fourth most disabling disease in the world, and the main clinical treatment is prevention. At present, the clinical diagnosis of knee osteoarthritis with deformation is mainly made by X-ray and two-dimensional ultrasound, and the preventive treatment effect is not good. Shear wave elastography (SWE) has been widely used in clinical practice for its advantages of noninvasive, simple, rapid, and high accuracy in soft tissue hardness. This study investigates the feasibility of using SWE in the grading diagnosis of KOA and the detection of early skeletal muscle injury. 60 patients were enrolled with unilateral KOA who met the inclusion criteria. Routine scanning and SWE exploration were carried out and compared between the affected and healthy knee joints. The measurements included morphology, damage degree of cartilage, joint effusion, joint synovial thickness, the degree of meniscus convexity, and shear wave speed (SWS) in the tendon attachment area of the quadriceps femoris superior patella, and tendon thickness and SWS between and within groups. The affected was scored according to the ultrasonic characteristics. The correlation between them was analyzed to evaluate the feasibility of SWE in grading the diagnosis of KOA. 57 cases had knee cavity effusion (57/60, 95.0%), 58 cases had knee cartilage injury (58/60, 96.6%), and 35 cases had a lateral process of the medial meniscus (35/60, 53.3%); 30 cases had synovial hyperplasia (30/60, 50%), 21 cases had osteophyte formation (21/60, 35%), and no one had a popliteal cyst. There was no significant difference in tendon thickness between and within groups ( > 0.05), but a significant difference in SWS ( < 0.01); the SWS of the quadriceps femoris tendon is negatively correlated with ultrasound score ( = 0.955, < 0.01). There is a strong negative correlation between SWS and the degree of KOA. It can be used in the grading diagnosis of KOA to help find more early strain points.