Since the early eighties arthroscopy has become an important part of orthopaedics. Virtually every joint can be examined with an arthroscope. Apart from the diagnostic possibilities, an increasing number of arthroscopically guided surgical operations are possible. Knee arthroscopy can be used therapeutically for many conditions, including meniscal lesions, refractory synovitis, cruciate ligament lesions, tibial plateau fractures and osteochondral defects; in the shoulder it can be applied to lesions of the glenoid lip or the rotator cuff; in the ankle and foot, for osteochondral fractures and creation of an arthrodesis; in the wrist, for treatment of instability, intra-articular distal fractures of the radius and the carpal tunnel syndrome; in the hip, for removal of loose bodies and in the spine, for the performance of discectomy. Advantages over conventional open operations are smaller proportions of complications (< 2%), shorter hospital stay and more rapid rehabilitation. The areas of indication are defined in guidelines issued by the orthopaedic societies themselves; most orthopaedic surgeons follow these guidelines. A possibility for the future is use of laser in interventions on joints.