Stryker Corp. SYK -0.24% agreed to acquire Mako Surgical Corp. MAKO +0.34%and its robotic-surgery platform for roughly $1.65 billion, a move aimed at distinguishing Stryker's line of replacement knees and hips for its increasingly cost-conscious hospital customers.

Mako shareholders will receive $30 a share, an 86% premium to the stock's Tuesday closing price. The Fort Lauderdale, Fla., company is expected to issue an additional four million shares in connection with the deal.

Mako makes a robotic arm designed to help surgeons more precisely implant replacement knees and hips during a procedure called Makoplasty. The product is complementary to Stryker's existing line of replacement hip and knee joints and could appeal to hospitals looking to improve procedural efficiency.

"Our combined expertise offers the potential to simplify joint reconstruction procedures, reduce variability and enhance the surgeon and patient experience," said Stryker President and Chief Executive Kevin A. Lobo in a written statement.

Markets reacted coolly to the deal, however, with some investors questioning the relatively high purchase price. Stryker shares were off 2.1% at $69.36 on the New York Stock Exchange at midday Wednesday.

"They're paying a lot—around 13 times this year's sales. That's a pretty big price," said Raj Denhoy, a medical-devices analyst at Jefferies & Co. "Stryker has shown its willingness to pay to expand into new areas."

The price also reflected the lengths that medical-device companies will go to jumpstart sales growth in the face of product commoditization and broad economic pressures that have led health-care providers and insurers to clamp down on costs. Stryker said that the addition of Mako would help it cater to hospital and insurance executives who increasingly want new devices to help reduce overall costs, a growing focus area for the devices industry.

"Robot-assisted procedures have the potential to aid hospitals, third-party payors and patients as they may reduce costs by shortening hospital stays and recovery periods and may reduce the amount of rehabilitation and medication," said Yin Becker, a Stryker spokeswoman, in an email. "We believe orthopaedic surgical robotics provides an opportunity to expand and grow significantly from its position today and has the potential to become a game-changing technology longer term."

Mako shares were up 82% at $29.50 on the Nasdaq Stock Market at midday Wednesday. As recently as March 2012, the stock traded for as high as $45. Mako's robots so far haven't experienced the uptake that many investors had initially hoped, said Jefferies' Mr. Denhoy. Knee implants in particular already have a high success rate, and some surgeons have questioned the robot's value. However, adoption of the company's hip-replacement product could improve because those procedures are thought to be more difficult.

In recent years, some patients have put off elective procedures because of the sluggish economy, which has slowed growth in the market for surgical knee and hip products. Meanwhile, hospitals looking to cut costs have pressured prices by reducing their number of suppliers.

In recent quarters, however, there have been signs of stabilization in the joint-reconstruction market. Stryker has said it expects revenue growth for the overall U.S. hip-and-knee market to rise in the low- to midsingle-digit range.

Stryker has sought to hedge against the sluggish orthopedics market by expanding its offerings in surgical tools and neurovascular products. The company, whose shares are up 26% year-to-date, is also recovering from a series of problems related to some of its devices that have resulted in product recalls.

The acquisition is expected to reduce Stryker's adjusted per-share earnings by about 10 cents to 12 cents in the first full year after it closes, be neutral in the second year and add to the bottom line after that.

A Mako representative wasn't immediately available to provide further comment.

Write to Joseph Walker at joseph.walker@wsj.com and Tess Stynes attess.stynes@dowjones.com

A version of this article appeared September 26, 2013, on page B9 in the U.S. edition of The Wall Street Journal, with the headline: Stryker Buys Robotic-Surgery Company.