Introduction: Intra-articular osteochondroma and acoustic neuroma are rare entities.
Case presentation: We report the rare occurrence of a para-articular osteochondroma of the knee developing over short duration, 5 months, following minor injury.
Conclusion: Predisposition to heterotrophic ossification after previous neurosurgery and a second acoustic neuroma may have accelerated the growth of this benign tumour. The development of these two rare entities suggests they may be associated.