Despite the high incidence of sarcopenia in the orthopaedic community, studies evaluating the influence of sarcopenia following primary total knee arthroplasty (TKA) are limited. Therefore, the purpose of this study is to determine if sarcopenic patients undergoing primary TKA have higher rates of (1) in-hospital lengths of stay (LOS); (2) medical complications; (3) implant-related complications; (4) fall risk; (5) lower extremity fracture risk; and (6) costs of care. Sarcopenia patients were matched to controls in a 1:5 ratio according to age, sex, and medical comorbidities. The query yielded 90,438 patients with ( = 15,073) and without ( = 75,365) sarcopenia undergoing primary TKA. Primary outcomes analyzed included: in-hospital LOS, 90-day medical complications, 2-year implant-related complications, fall risk, lower extremity fracture risk, and costs of care. A -value of less than 0.05 was considered statistically significant. Patients with sarcopenia undergoing primary TKA had greater in-hospital LOS (4 vs. 3 days,  < 0.0001). Sarcopenic patients were also found to have increased incidence and odds of 90-day medical complications (2.9 vs. 1.1%; odds ratio [OR] = 2.83,  < 0.0001), falls (0.9 vs. 0.3%; OR = 3.54,  < 0.0001), lower extremity fractures (1.0 vs. 0.2%; OR = 5.54,  < 0.0001), and reoperation (0.9 vs. 0.5%; OR = 1.87,  < 0.0001). Additionally, sarcopenic patients had greater 2-year implant-related complications (4.3 vs. 2.4%; OR = 1.80,  < 0.0001), as well as day of surgery ($52,900 vs. 48,248,  < 0.0001), and 90-day ($68,303 vs. $57,671,  < 0.0001) costs compared with controls. This analysis of over 90,000 patients demonstrates that patients with sarcopenia undergoing primary TKA have greater in-hospital LOS, increased odds of 90-day medical complications, falls, lower extremity fractures, and reoperations. Additionally, sarcopenia was associated with greater 2-year implant-related complications, day of surgery costs, and 90-day costs. The study is useful as it can allow orthopaedic surgeons to properly educate these patients of the potential complications which may occur following their surgery.