[Paul L]

I haven't researched this in several years, but in California, the leading case on this issue was (and presumedly still is) as follows:

During a Super Bowl halftime informal touch football game including women and men, defendant ran into plaintiff from behind, knocked her down, and stepped on her hand. Defendant continued running until he tagged a ball-carrier hard enough to sprain her ankle. On the preceding play, plaintiff had complained about defendant’s excessively rough play. After several surgeries, Plaintiff's finger was amputated.

California Supreme Court said: ‘A participant in an active sport breaches a legal duty of care to other participants-i.e., engages in conduct that properly may subject him or her to financial liability-only if the participant intentionally injures another player or engages in conduct that is so reckless as to be totally outside the range of the ordinary activity involved in the sport. Defendant was, at most, careless or negligent in knocking over plaintiff, stepping on her hand, and injuring her finger. The conduct is not even closely comparable to the kind of conduct-conduct so reckless as to be totally outside the range of the ordinary activity involved in the sport-that is a prerequisite to the imposition of legal liability upon a participant in such a sport. Defendant was, at most, careless or negligent in knocking over plaintiff, stepping on her hand, and injuring her finger. Accordingly, this case falls within the primary assumption of risk doctrine, and thus the trial court properly granted summary judgment in favor of defendant.’
Knight v. Jewett (1992) 3 Cal.4th 296