M25.46Non-Billable (Header)Effusion, kneeChild CodesM25.461Effusion, right kneeM25.462Effusion, left kneeM25.469Effusion, unspecified kneeCode Hierarchy└M25Other joint disorder, not elsewhere classified└M25.4Effusion of joint└M25.46Effusion, knee└M25.46Effusion, knee