Table 1.

Stages of joint infection [5]

Gächter	The classification according to Gächter included IV Stages:
Stage I	Opacity of fluid, redness of the synovial membrane, possible petechial bleeding, no radiological alterations.
Stage II	Severe inflammation, fibrinous deposition, pus, no radiologic alterations.
Stage III	Thickening of the synovial membrane, compartment formation ("sponge-like" arthroscopic view, especially in the suprapatellar pouch), no radiologic alterations.
Stage IV	Aggressive pannus with infiltration of the cartilage, possibly undermining the cartilage, radiological signs of subchondral osteolysis, possible osseous erosions and cysts.
Jensen	The classification according to Jensen included III stages:
Stage I	Opaque effusion with high cell count, hyperaemia of the synovium.
Stage II	Putrid effusion, fibrin coatings, synovial hypertrophy with petechial bleeding.
Stage III	Severe villous synovitis with (partial) tamponade of the joint, synovial necrosis, synovial adhesions, cartilage destruction.
Kuner	The classification according to Kuner was more a clinical description rather than an arthroscopic staging:
Stage I	Purulent synovitis
Stage II	Joint empyema
Stage III	Panarthritis
Stage IV	Chronic arthritis.