The Minnesota Twins announced Friday afternoon that All-Star slugger Miguel Sano had been activated after missing the last 38 days while recovering from a stress reaction in his left tibia (shin bone). This news couldn’t come at a better time as the Twins, fresh off clinching the second Wild Card spot and their first playoff appearance in seven years, only have three games remaining on their schedule, which leaves limited time for Sano to acclimate again to major league pitching. (Note: Sano is not in the lineup for tonight’s game against the Detroit Tigers.)

Sano, who owns the team’s highest OPS at .870 and is second in home runs (28), is an integral component of the Twins’ lineup and could provide the team with a big – literally and metaphorically – jump in win probability in their one-game series against the New York Yankees. But will his pain due to his stress reaction linger? Will it affect his swing once he is reinserted into the lineup? What exactly is a stress reaction, anyway?

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A stress reaction is the starting point of the Bone Stress Injury continuum and may progress to a stress fracture if not treated appropriately.

The Bone Stress Injury continuum flows as follows: healthy bone – stress reaction – stress fracture – complete fracture.

Bone stress injuries occur when the bone, in this case Sano’s tibia, is unable to repair from microtrauma suffered as a result of repetitive loading. Think of the effect of jogging on the heel, for example. The difference between a stress reaction and a stress fracture is that there is a definitive “crack” (fracture line is the more technical term) on imaging in a stress fracture, whereas a stress reaction simply has an accumulation of fluid and tenderness within the bone.

The tibia is one of the most common sites of bone stress injuries due to its function as a primary load-bearer and force distributor in the body; it is estimated that 33-55% of all stress fractures occur in the tibia. There are myriad factors that contribute to the development of a bone stress injury including but not limited to: hormonal imbalances, diet (specifically low fat/calorie diets), muscle strength imbalances, and abrupt increases in workout intensity.

Much like with all types of fractures, the best treatment for bone stress injuries is simply time; the bone needs time to rebalance its bone building (osteoblastic) and bone breakdown (osteoclastic) activity. The typical rehabilitation progression for bone stress injuries includes rest, followed by low-intensity/impact training (jogging, soft-toss, hitting off a tee, etc.), and then high-intensity/impact training (weight-lifting, hitting off pitchers, simulated games, etc.).

The player is shuffled through these steps throughout the course of 4-8 weeks (typically) with pain tolerance being the most important factor for determining advancement. If the player experiences too much pain they either revert to the previous step or remain at where they’re at. If they don’t have pain, they advance.

Prior to getting the nod by the Twins training staff Friday afternoon, Thad Levine in an interview with KSTP and ESPN 1500’s Darren Wolfson stated that Sano had expressed to the Twins that he was ready to return after facing pitchers and taking swings over the last few days. This will be important to monitor as next Tuesday looms nearer; if Sano is able to continue swinging without suffering from some much pain that it forces him to discontinue, he should be ready, physically at least, to play against the Yankees.

At this point, Sano shouldn’t be at too great of a risk for causing further damage. All signs point to the Twins handling Sano’s injury as well as they possibly could, so the only limiting factor in determining whether or not he is good to go against the Yankees is pain tolerance. And when it comes to playing in the team’s first playoff appearance in some time, I’d imagine Sano’s pain tolerance may be pretty high.

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Academic sources of information for this article:

1. Feldman JJ, Bowman EN, Phillips BB, and Weinlein JC. Tibial stress fractures in athletes. Orthop Clin N Am. 2016; 47: 733-741
2. Warden SJ, Davis IS, Fredericson M. Management and prevention of bone stress injuries in long-distance runners. JOSPT. 2014; 44(10): 749-765
3. Zadpoor AA and Nikooyan AA. The relationship between lower-extremity stress fractures and the ground reaction force: A systematic review. Clinical Biomechanics. 2011; 26: 23-28

Lucas Seehafer

Lucas is a third-year doctor of physical therapy graduate student and likes to write about sports in his free time. In addition to Zone Coverage, his writing can be found at A Wolf Among Wolves.

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