Objective: To determine whether physical examination maneuvers that focus on each knee compartment and assess crepitus at several distinct sites can specifically disclose articular cartilage abnormalities in the compartment being assessed.
Methods: Twenty patients with knee pain were examined before needle arthroscopy. Crepitus was sought from the patellofemoral compartment, medial tibiofemoral compartment, and lateral tibiofemoral compartment. Any crepitus felt in the distal tibia during a tibiofemoral stress maneuver was recorded as transmitted bony crepitus (TBC). Needle arthroscopy assessed articular cartilage (5 sites) and both menisci in each knee.
Results: Crepitus by conventional assessment revealed patellar cartilage disruption (69% sensitive, 50% specific) and abnormalities of tibiofemoral cartilage (67% sensitive, 40% specific) but could not indicate their location. Tibiofemoral crepitus found cartilage disruption in the compartment at a sensitivity of 22% and a specificity of 100%, and with added tibiofemoral stress, a sensitivity of 65% and a specificity of 94% (the one "false positive" had bare bone in the other compartment). TBC was detected in 7 compartments, all of which had focal bare bone on tibial and femoral surfaces; 6 other compartments had tibial bare bone without TBC. Thus, TBC was 54% sensitive and 100% specific for tibial bare bone, and 88% sensitive and 100% specific for bone-on-bone.
Conclusion: Compartment-directed physical examination of the painful knee can locate and assess the severity of certain articular cartilage abnormalities that are not reliably found by conventional methods. Transmitted bony crepitus is a specific finding for bone-on-bone in the compartment being assessed.