Compressive and frictional properties of IPN hydrogels. PAAm = polyacrylamide, Alg = alginate, Fib = fibrin, Alg/PAAm = alginate/polyacrylamide & Fib/PAAm = fibrin/polyacrylamide) (A) PCL scaffold alone, PCL/Alg/PAAm-IPN composite, cartilage, and Alg/PAAm strain recovery following 10% strain, (B) Stress-strain behavior of the hydrogels during compression, (C) Young’s modulus of the hydrogels calculated from unconfined compression studies. * P < 0.05 for Alg/PAAm vs. PAAm, Alg, Fib and Fib/PAAm. + P < 0.05 for Fib/PAAm vs. PAAm and Fib. (D) Coefficient of friction of the hydrogels determined using a rheometer. * P < 0.05 for Alg vs. Alg/PAAm, Alg, & Fib/PAAm. + P < 0.05 for Fib vs. PAAm, Alg/PAAm and Fib/PAAm.