As long as it's not too high, saw a few ohms, then it won't make much difference.

Let's say the output signal is 0.3v/300mV. That's running into a typical guitar amp input impedance of 1meg ohms.

So from Ohm's law the current generated is 0.3 V/1,000,000 ohms = 0.0000003A

If the joint had a 10 ohm resistance (and it's more likely to be more like 2 ohms), and being two joints which would give 20 ohms total resistance, then the volt drop across that would be 0.0000003A x 20 ohms = 0.000006 V. Which would be a signal drop of just 0.002%, so nothing to be concerned about in itself. However, from a guitar grounding point of view, the lower the resistance to ground the better, so you are more likely to pick up a bit more noise from the guitar as a result.