Out of those cruciferous vegetables, which include broccoli, cauliflower, Brussels sprouts, kale, cabbage and bok choy among others, broccoli has shown the most consistent and pronounced anticancer effects with testing.
The types of broccoli grown and how it's prepared determine its anticancer power. The amount that has to be eaten for high anticancer activity may be too much for most except the most ardent broccoli lovers.
But recently, a more accessible variation of broccoli has been proven so potent at delivering anticancer compounds that one group attempted to patent it; fortunately, they were unsuccessful.
Now the same anti-cancer compound in broccoli has been tested positively for its effects on existing osteoarthritis or degenerative joint disease, a very common, painful and debilitating degenerative joint condition that afflicts an estimated 20 million people or more in the USA alone.
Older folks are most likely to suffer from osteoarthritis, as joint wear and tear increases inflammation.
What the anticancer compound is and how it's been testedThe anticancer compound is sulfur-based sulforaphane. It doesn't come gift wrapped in broccoli, but the naturally occurring precursor glucoraphanin that creates it does.
So it's the glucoraphanin content that varies with different broccoli and is essential for creating sulforaphane, releasing Phase-2 enzymes which neutralize highly reactive forms of cancer-causing chemicals before they can damage DNA and promote cancer. 
A very recent test of broccoli's sulforaphane creation and activity was focused on osteoarthritis instead of cancer. The UK's University of East Anglia in vitro (petri dish) study showed that sulforaphane blocked a key inflammatory enzyme. Inflammation is the root of osteoarthritis
They also completed in vivo (animal) studies showing that mice fed a diet high with broccoli's glucoraphanin-producing sulforaphane had significantly less joint cartilage than mice who had less sulforaphane. The study was published in the journal Arthritis & Rheumatism. 
Now this same team will pursue a human trial. They even created a super broccoli hybrid they call Beneforte, which 20 knee replacement patients will consume 3.5 ounces daily for two weeks before their surgeries. Another 20 similar patients will not consume the Beneforte broccoli. All 40 removed tissues will be compared after their knee replacement surgeries. 
Most guys know that consuming lots of heated tomato products is a good way to enjoy Italian foods and protect against prostate cancer with the anticancer agent lycopene.
But combining cooked tomatoes with broccoli has been shown to offer cancer preventative properties higher than either food alone. The animal (rat) study to determine this was conducted by the University of Illinois at Urbana-Champaign and the Solove Research Institute of Columbus, Ohio. It was published in the 2007 issue of Cancer Research. 
The most potent broccoli tested and contestedIn 1997, Johns Hopkins University discovered that broccoli sprouts had 20 to 50 times the glucoraphanin to sulforaphane capacity as regular broccoli. They were so impressed with what they found that they formed Brassica Protection Products LLC and patented their findings.
Then they played Monsanto and sued individual commercial broccoli sprout farmers to eliminate the existing competition. Naughty-naughty Johns Hopkins. Fortunately, the farmers united and formed a defense that prevailed even after Brassica's appeal in 2002.
The Maryland judge ruled, ... "merely describing unexpected beneficial results of a known process does not entitle Plaintiffs (Brassica Protection Products) to patent that process." Finally, some justice in the justice system. 
Due to exaggerated E. coli concerns, some commercial broccoli sprout cultivators have resorted to using bleach as a disinfectant. That's not too healthy. The FDA recommends cooking them. Both of these measures disrupt enzymes and healthy compounds in those sprouts.
Your options are buying organically produced broccoli sprouts, which are difficult to find and expensive, or better yet, simply sprouting your own organic broccoli seeds.