This pilot study aimed to investigate the effects of Nandrolone decanoate, an anabolic steroid, on post-total knee arthroplasty (TKA) recovery and muscle strength. The study also assessed the drug's safety in patients with multimorbidity. A double-blind randomized study design was employed, with patients receiving either Nandrolone decanoate or a saline placebo intramuscularly biweekly for six months. The steroid group consisted of patients with an average BMI of 40.9 and a mean age of 65.2. The control group comprised five participants with ages ranging from 55 to 70 and BMI ranging from 20.5 to 34.5, who received saline injections. Knee society scores (KSS) and functional tests (sit-to-stand, timed walking) were conducted at specified intervals, along with bone mineral density scans to measure changes before and after surgery. The steroid group consistently outperformed the control group in all functional tests based on analysis of variance (ANOVA). After 6, 18, and 24 months of postoperative recovery, the steroid group exhibited significant improvements in quadriceps muscle strength compared to the control group. Furthermore, significant differences in KSS scores were observed at six weeks, 6 months, and 24 months, indicating a better overall outcome in the steroid group. However, the steroid group did not show a statistically significant change in bone mineral density from pre- to post-surgery, despite reductions in lumbar spine and femur mineral density during the surgical procedure. This pilot study suggests that the use of Nandrolone decanoate following TKA may lead to improved functional outcomes and quadriceps muscle strength during postoperative recovery. Further research with a larger sample size is warranted to validate these findings and evaluate long-term safety considerations