Claudication of the young patient is a very rare symptom for orthopaedic surgeons and it is often overlooked. We report a rare case of popliteal artery entrapment syndrome (PAES), discovered during a vascular claudication following post-traumatic anterior instability of the knee. The diagnosis was confirmed by CT angiography which showed a PAES, with a pathway in the inter-condylar notch. The patient had a releasing of the trapped vessel by myomectomy, with disappearance of vascular symptoms six months later. Through this case, we wanted to draw the attention of orthopaedic surgeons to the fact that the PAES can be asymptomatic. Its symptomatology can be triggered by a traumatic instability of the knee. Its presence represents a risk of lesion of the popliteal artery during arthroscopic ACL reconstruction. Therefore, it is important to think about this disease if a calf pain occurring after a ligament injury of the knee.