Objective: To compare quantitatively the error made in knee joint proprioception by typically developing and spastic diplegic children of age 5-12 years. Design: Cross sectional. Participants: A total of 100 subjects were recruited, out of which, 80 (40 males, 40 females) were typically developing children (mean ---PlusMinusSymbol--- standard deviation of age was 8.88---PlusMinusSymbol--- 2.29 years) and 20(13 males, 7 females) were children with spastic diplegia (mean ---PlusMinusSymbol--- standard deviation of age was 9.54---PlusMinusSymbol--- 2.44 years). Methods: Passive reproduction of joint position of knee was checked by using a universal goniometer. Relative error was measured in degrees. Results: Mean ---PlusMinusSymbol--- standard deviation of relative error in knee joint proprioception was 12.91---PlusMinusSymbol---5.63 degrees for children with spastic diplegia and 1.80---PlusMinusSymbol---2.15 degrees for typically developing children respectively. Comparison of the relative error between spastic diplegic children and typically developing children using the Mann-Whitney U test was highly significant with p value < 0.001 Conclusions: There was significant error in proprioception of knee joint in children with spastic diplegia as compared to typically developing children.