When considering any stock for your portfolio, don't be swayed by just the positives. Examine its pros and cons, and decide whether it's possible upside outweighs its risks. Let's take a look at MAKO Surgical (UNKNOWN:MAKO.DL) today, and see why you might want to buy, sell, or hold it.

Founded in 2004, based in Florida, and with a recent market capitalization of $480 million, MAKO is in the business of making medical devices -- specifically, RIO Surgical robotic equipment and orthopedic implants. Its main offerings involve partial-knee arthroplasties and total hip replacements.

MAKO's business arena is one big draw, thanks in part to our world's growing and aging population. (Our obesity problem helps as well, as obesity can accelerate knee and hip degeneration.) According to my colleague Brenton Flynn, knee and hip procedures have been growing faster than the overall population, which bodes well.

The company's revenue has been growing steadily, but its net income has remained negative. On the plus side, though, the losses have represented a shrinking portion of revenue. And while recently reported fourth-quarter earnings disappointed many investors, they were in line with company projections and do reflect continued growth and market acceptance. In 2012, the number of RIO procedures completed rose 29% over year-earlier levels.

Another plus is quality, as the RIO systems offer below-average failure rates.

One strike against the company is that its current offerings remain a bit limited in scope, addressing just partial knee replacements, for example, and not total replacements. The company's performance in 2012 is also not auspicious, as it underperformed sales expectations and saw its stock plunge some 49%. (The stock soared more than 60% in 2009 and 2011, and more than 30% in 2010. These numbers also point to another drawback for some: volatility. If you can't handle wide swings, steer clear.)

The stock's valuation doesn't reflect a screaming buy. Due to negative earnings, there's no P/E ratio, and the recent price-to-sales ratio of 4.5 -- while below the company's five-year average of 15.3 -- is well above the S&P 500's 1.4 and the industry's 2.1.

Dilution is another concern, as MAKO's share count has been inching up. That's not necessarily a dealbreaker, as funds generated from share issuances can help further growth. But adding shares does reduce the stake in the company claimed by the earlier shares.

MAKO has powerful competition, too, or potential competition, such as from Intuitive Surgical (NASDAQ:ISRG), which has a market value nearly 50 times greater than MAKO and has been posting strong double-digit growth in both revenue and earnings in recent years, with more and more hospitals buying its million-dollar daVinci machines. Right now, Intuitive's business and MAKO's don't really cross paths.

An even bigger competitor, which is involved some of the same work as MAKO, is Johnson & Johnson (NYSE:JNJ), which has a unit focused on orthopedic devices that generates more than $6 billion in revenue annually -- in addition to other medical device businesses. Stryker and Zimmer Holdings (NYSE:ZMH) are also working in orthopedic devices. Zimmer recently received the FDA's blessing for a new guidance system for knee replacement procedures. Meanwhile, there's a new competitor on the block -- Blue Belt Technologies, with an FDA-approved orthopedic robotic surgical system.

Finally, there's the new 2.3% tax on medical devices that companies such as MAKO will be required to pay. And as my colleague Dan Carroll has pointed out, it will hit unprofitable companies such as MAKO hard, as they won't be able to pay it out of earnings.

Hold (off)
Given the reasons to buy or sell MAKO Surgical, it's not unreasonable to decide to just hold off on it. You might want to wait for it to be offering machines that perform a wider range of procedures, or for its net losses to turn into net gains, ideally for a string of quarters.

You might also check out some other interesting related companies, to see if they seem like better bargains than MAKO. Perhaps take a look at Accuray (NASDAQ:ARAY), which specializes in radiosurgery and radiotherapy. Its stock is down some 42% over the past year, leading some to see it as bargain-priced now, with a recent price-to-sales ratio below 1. But it recently projected declining revenue due to manufacturing and supply issues. It's worth learning more before jumping in.

The verdict
I'm actually a shareholder in MAKO already, though I'm underwater on it. It does seem potentially promising to me, but it's far from low-risk. Everyone's investment calculations are different, though. Do your own digging and see what you think. The company may perform spectacularly in the coming years, but remember that there are plenty of compelling stocks out there.

Longtime Fool contributor Selena Maranjian, whom you can follow on Twitterowns shares of Johnson & Johnson, MAKO Surgical, and Intuitive Surgical. The Motley Fool recommends Intuitive Surgical, Johnson & Johnson, and MAKO Surgical. The Motley Fool owns shares of Intuitive Surgical, Johnson & Johnson, and Zimmer Holdings. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.