We calculate the fractal dimension d f of critical curves in the O(n) symmetric ( φ 2 ) 2 -theory in d = 4 − ε dimensions at 6-loop order. This gives the fractal dimension of loop-erased random walks at n = −2, selfavoiding walks (n = 0), Ising lines (n = 1), and XY lines (n = 2), in agreement with numerical simulations. It can be compared to the fractal dimension d tot f of all lines, i.e. backbone plus the surrounding loops, identical to= νd f is the crossover exponent, describing a system with mass anisotropy. Introducing a novel self-consistent resummation procedure, and combining it with analytic results in d = 2 allows us to give improved estimates in d = 3 for all relevant exponents at 6-loop order.