Abstract Background The long-term risk from knee intra-articular (KIA) injections in professional athletes such as ex-footballers remains unknown. The use of KIA injections is controversial and remains anecdotally prolific as it is perceived as being safe/beneficial. The aim of this study was to determine the number, type and frequency KIA injections administered to retired professional footballers during their playing careers and the associations with post-career knee osteoarthritis (KOA). Methods This is a cross-sectional study involving a postal questionnaire (n = 1207) and subsequent knee radiographs in a random sample of questionnaire responders (n = 470). Footballers self-reported in the questionnaire whether they had received KIA injections and the estimated total number over the course of their playing career. Participant characteristics and football career-related details were also recorded. KOA was measured as self-reported knee pain (KP), total knee replacement (TKR) and radiographic KOA (RKOA). Results 44.5% of footballers had received at least one KIA injection (mean: 7.5; SD ± 11.2) during their professional career. 71% of knee injections were cortisone/corticosteroid based. Multivariate logistic regression, adjusting for age, body mass index (BMI) and significant knee injury identified that footballers with injections were two times more likely to have KP (OR 1.81, 95% CI 1.40–2.34) and TKR (OR 2.21, 95% CI 1.43–3.42) than those without injections. However, there was no association with RKOA (OR 1.30, 95% CI 0.85–2.01). Given, the association with KP and TKR, we found a significant dose–response relationship as the more injections a player received (by dose–response groups), the greater the risk of KP and TKR outcomes after adjustment for knee injury and other confounders (p for trend < 0.01). Conclusion On average, 8 KIA injections were given to the ex-footballers during their professional career. The most commonly administered injections were cortisone based. These injections associated with KP and TKR after they retired. The associations are independent of knee injuries and are dose dependent. The study suggests that there may have been excessive use of KIA injections to expedite return to play and this contributed to detrimental long-term outcomes such as KP and TKR post-retirement from professional football.