Extra-articular deformities (EAD) can pose a challenge to surgeons during a total knee arthroplasty (TKA) surgery. Obtaining an acceptable post-operative hip-knee-ankle (HKA) angle may be difficult, especially in a limb with multiplanar deformities of both the femur and the tibia. Our case is about a 66-year-old gentleman with a long-term deformity of his right lower limb secondary to malunion of the right femoral shaft and tibial shaft fractures. He initially presented with a right floating knee injury, 45 years ago, which was managed with conservative measures. He subsequently presented to us with ipsilateral knee osteoarthritis and underwent a robotic-assisted total knee arthroplasty surgery. Robotic- or computer-assisted total knee arthroplasty is an actively developing area and is gaining popularity among arthroplasty surgeons. In cases with severe extra-articular deformities such as in this case, robotic-assisted surgery can be superior to conventional surgery.