Background: Injection site pain is not uncommon after interventional procedures particularly after platelet-rich plasma (PRP) injection. This retrospective study aims to find out the incidence of post-injection pain after injection and any relation of post-injection pain with injection site in PRP injection for osteoarthritis of the knee. Methods: Patients of osteoarthritis of the knee who received PRP injection were grouped into two. Group A received PRP injection at the superolateral approach and group B received PRP injection at the inferolateral approach. Pre-procedure pain score on verbal rating score and post-procedure injection pain were compared in both the group and post-procedure injection pain were compared between the two groups. Results: The sample size was calculated accepting alpha error as 0.05 and power of study 80%. The inferolateral approach was thought to be more painful because of narrowing of injection space and mean pain score was presumed as 6/10 ± 1 on the verbal rating scale (VRS). The superolateral approach was considered as less painful and anticipated pain score on VRS was 5/10. The calculated sample size was 16 in each group. However, in our study sample size were 35 in group A and in group B, it was 34. Demographic profiles were compared using students t-test and Chi-square test and the two groups were found similar in age and sex ratio. Pain score of two groups was compared using the Mann–Whitney U test and was found comparable (6.31 ± 1.1 in group A and 5.76 ± 1.46 in group B). Post-injection pain at 7 days was compared between groups and was also found similar (4.62 ± 1.7 in group A and 4.74 ± 1.4 in group B) without any statistically significant difference between two groups. Pre-procedure pain (6.04 ± 1.31) in both groups compared with post-injection pain (4.68 ±1.55) of both groups and were found less than pre-injection pain and was found statistically significant (p < 0.00001). Discussion: Post-injection pain after 7 days after PRP injection were found to be less than pre-procedure injection and there is no relation pain with the injection site.