Anterior bony impingement of the ankle is a common cause of chronic ankle pain, and it represents an important indication to arthroscopic treatment.

The purpose of the study was to analyze the factors affecting the clinical outcome of surgical treatment and to describe a new classification based upon the arthroscopic assessment, considering prognostic factors and rationale for treatment.

84 consecutive patients with a mean age of 32.6 years were treated between 2000 and 2005. The impinging lesions were divided into localized (antero-medial, antero-lateral and syndesmotic) or diffuse. The status of the chondral layer (A – Normal; B – Focal ICRS grade I–II; C - Focal ICRS grade III–IV; D – Diffuse ICRS grade I–II; E – Diffuse ICRS grade III–IV) was documented, as well as the presence of altered foot morphology (cavus or flat) or ligament lesions. Previous traumas or surgery were considered. Patients were evaluated after a 24–87 months follow-up, following the AOFAS scale.

The pre-operative AOFAS score was 39.4, while at follow-up it scored 80.1(p< 0.05). Patients with diffuse anterior impingement obtained the best result in terms of improvement. Patients with normal cartilage had a better outcome but among cartilage lesions the better improvement was obtained in patients with diffuse severe cartilage damage. Associated regenerative treatment for focal chondral grade III–IV lesions provided the better results. Patients with associated surgically repaired ligament lesions had the better clinical outcome with respect to intact ligaments.

On the basis of the results we purpose a new classification, based upon the prognostic factors, into 2 types: I – Localized; II - Diffuse. Further classification was made into subtypes A to E according to the associated chondral lesions. Finally the presence of associated conditions such as ligament lesions, previous sprains or surgery was considered, being relevant as prognostic factors.