comma before present participle: hurt his knees, playing soccer

[8769]

I’m interested in the use of punctuation.

Which is more common, #1 or #2, below?
1. Bill hurt his knees playing soccer in the park.
2. Bill hurt his knees, playing soccer in the park.

I have long thought #2 is, but I recently found #1 in *a grammar book published here in Japan. What do you think?
(*from p.239 of K. Yoshinami, et al’s ”Breakthrough English Grammar” from Biseisha, 2011, Kyoto, Japan)

 

[panjandrum]

I wouldn't put a comma in this sentence.
I think I can see why others would.

The clause "playing soccer in the park" is not essential to the sentence, it adds further information.
As such, it would often be separated from the rest of the sentence by "bracketing commas".
Playing soccer in the park, Bill hurt his knees.
Bill, playing soccer in the park, hurt his knees.

But when placed in final position in the sentence the "bracketing comma" may be omitted.

See http://www.informatics.sussex.ac.uk...ation/node13.html#SECTION00044000000000000000

In many cases a weak interruption does not absolutely require bracketing commas. Thus either of the following is fine:
Shortly before the war, he was living in Paris.
Shortly before the war he was living in Paris.