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Background:Several systems have been proposed for classifying osteochondritis dissecans (OCD) of the knee during surgical evaluation. No single classification includes mutually exclusive categories that capture all of the salient features of stability, chondral fissuring, and fragment detachment. Furthermore, no study has assessed the reliability of these classification systems.Purpose:To determine the intra- and interobserver reliability of a novel, comprehensive arthroscopic classification system with mutually exclusive OCD lesion types.Study Design:Cohort study (diagnosis); Level of evidence, 3.Methods:The Research in OsteoChondritis of the Knee (ROCK) study group developed a classification system for arthroscopic evaluation of OCD of the knee that includes 6 arthroscopic categories—3 immobile types and 3 mobile types. To optimize comprehensibility and applicability, each was developed with a memorable name, a brief description, a line diagram corresponding to the archetypal arthroscopic appearance, and an arthroscopic photograph depicting this archetype. Thirty representative arthroscopic videos were evaluated by 10 orthopaedic surgeon raters, who classified each lesion. After 4 weeks, the raters again classified the OCD lesions depicted in the 30 videos in a new, randomly selected order. Reliability was assessed via the intraclass correlation coefficient (ICC).Results:The interobserver reliability of this novel arthroscopy classification was estimated by an ICC of 0.94 (95% CI, 0.91-0.97) for the first round and 0.95 (95% CI, 0.93-0.98) for the second round. According to the standards for the magnitude of the reliability coefficient of Altman, these ICCs indicate that interobserver reliability was very good. The intraobserver reliability was estimated by an ICC of 0.96 (95% CI, 0.95-0.97), which indicates that the intraobserver reliability was similarly very good.Conclusion:The ROCK OCD knee arthroscopy classification system demonstrated excellent intra- and interobserver reliability. In light of this reliability, this classification system may be used clinically and to facilitate future research, including multicenter studies for OCD.

We report the case of a four-year-old girl who died within hours after she was seen for pain in the knee and varicella. The death was due to fulminant sepsis with group-A Streptococcus. The postmortem examination revealed a bacterial infection of the varicella skin lesions, which resulted in bacteremia leading to generalized sepsis. The pain in the knee was initially thought to be secondary to septic arthritis, varicella arthritis, or osteomyelitis, but it was diagnosed after death as septic popliteal thrombophlebitis associated with fulminant group-A streptococcal septicemia. We report the case of our patient to bring attention to this rare but life-threatening cause of pain in the knee. A four-year-old girl was seen in the emergency room at Children's Hospital because of pain in the left knee of two days' duration. Two weeks before admission, she had an ear infection that was treated with sulfa compounds. Six days before admission, a diffuse vesicular rash, consistent with varicella, developed. Four to five days before admission, the child had a fever while she was at home, but it was not measured. Two days before admission, she began to have pain in the left knee that steadily increased in severity such that, by the time of admission, she was unable to bear weight on the left lower limb. The medical history was unremarkable. She had an allergy to penicillin. On the morning of admission, the patient was seen at an outside clinic, where laboratory studies revealed a white blood-cell count of 8.7 x 109 per liter (8700 per cubic millimeter), a platelet count of 119 x 109 per liter (119,000 per cubic millimeter) (normal, 150 to 400 x 109 per liter [150,000 to 400,000 per cubic millimeter]), and an erythrocyte sedimentation rate of twenty-five millimeters per hour (normal, zero to …