Something that I decided to look into because of my own personal observations.
There seems to be mounting evidence that player concussions are accompanied by significant increased risk to subsequently incurring musculo-skeletal injuries, especially lower extremity injuries. The medical literature has identified dynamic postural control deficits along with increased motor evoked potential latency (slow down of nerve responses) and decreased amplitude of nerve conduction) after concussion, suggesting that the brain may be unable to effectively coordinate movement.
A European study of 46 male elite football (soccer) teams in 10 European countries in the 2001/2002–2011/20122 seasons was published in the British Journal of Sports Medicine in July 2014. During the follow-up period, 66 players sustained concussions and 1599 players sustained other injuries. Compared with the risk following other injuries, concussion was associated with a progressively increased risk of a subsequent injury in the first year (0 to <3 months......1.56 times risk; 3 to <6 months.........2.78 times risk; 6–12 months, 4.07 times risk).
In Dec 2015, a study published in the Journal of Medical Scientific Sports Exercise, investigated collegiate athlete acute lower extremity musculoskeletal injury rates before and after concussion in athletes with concussion and their matched control. Nonconcussed college athletes were matched to individuals with concussion. Acute lower extremity musculoskeletal injury data were collected for 2 yr (±1 yr of the diagnosed concussion) using electronic medical records. Control participants' 2-yr window for exposure and musculoskeletal injury data were anchored to their match's concussion injury date. Pre- and postconcussion musculoskeletal injury rates were calculated for 90-, 180-, and 365-day periods for both study cohorts. Risk ratios were calculated to determine differences within and between groups for all periods. Within 1 yr after concussion, the group with concussion was 1.97 times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion and 1.64 times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than their matched nonconcussed cohort over the same period. Up to 180 d after concussion, the group with concussion was 2.02 times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion.
Next, a recent study published May 2017 in The Journal of Sports Medic`ine, collected injury data from 2006 to 2013 for men’s American football and for women’s basketball, soccer and lacrosse at a National Collegiate Athletic Association Division I university. Ninety cases of in-season concussion in 73 athletes (52 male, 21 female) with return to play at least 30 days prior to the end of the season were identified. A period of up to 90 days of in-season competition following return to play was reviewed for time-loss injury. The same period was studied in up to two control athletes who had no concussion within the prior year and were matched for sport, starting status and position. Lower extremity musculoskeletal injuries occurred at a higher rate in the concussed athletes (50 %) than in the non-concussed athletes (20 %). The odds of sustaining a musculoskeletal injury were 3.39 times higher in the concussed athletes.
All of these post concussion injury numbers are consistent with something neurological affecting the longer-term coordination of the concussed player leading to subsequent injuries.