A pragmatic approach to the imaging and follow-up of solitary central cartilage tumours of the proximal humerus and knee

Central cartilage tumours of bone range from the benign enchondroma to the malignant chondrosarcoma. They are an incidental finding in up to 2.8% of routine magnetic resonance imaging (MRI) examinations performed of the shoulder and knee. The purpose of this review is to provide a current appraisal of the imaging and histological challenges of distinguishing enchondroma from low-grade chondrosarcoma. The general radiologist, encountering these lesions in the proximal humerus and around the knee, is introduced to the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP). This provides a guide to the initial assessment and diagnosis, a stepwise imaging follow-up plan, and the indications for onward specialist orthopaedic oncology referral or discharge from follow-up.