Introduction Platelet-rich plasma (PRP) intra-articular injections have gained popularity and are suggested to be more effective and longer lasting than corticosteroid or visco-supplementation therapy. There are few studies comparing PRP with corticosteroid injections and none comparing PRP in patients with bilateral knee osteoarthritis with the patient acting as their own control. Methods We performed a double-blind randomized controlled trial including 29 patients (58 knees) with radiologically confirmed mild-to-moderate bilateral knee osteoarthritis. They were randomized to receive an intra-articular PRP injection into one knee and a methylprednisolone injection with a local anesthetic into the contralateral knee. The primary outcome was measured using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) before the treatment and at six weeks, three months, and six months. Secondary outcome was measured pain with the visual numerical pain rating scale (VNS). Results Corticosteroids and PRP were both effective in improving pain, stiffness, and function at all time points, with maximal improvements at six weeks and three months. PRP scored slightly better than steroid injections at six months; nevertheless, there was no statistically significant difference between corticosteroids and PRP injections (F2,139=0.173, p=0.84). The secondary outcome also delivered the same result with improvement at all time points but no statistically significant difference (F2,139=0.168, p=0.85). Conclusions Both corticosteroids and PRP interventions are effective in improving pain, stiffness, and function in patients with bilateral knee osteoarthritis up to six months with no statistically significant difference between the two.