Return to play and recurrence after calf muscle strain injuries in elite Australian football players

Key points

1. 01Severe aponeurotic disruption (AD) on MRI was linked to significantly longer return-to-play periods compared with no AD (31.3 vs 19.4 days)
2. 02A running-related mechanism of injury was the strongest independent predictor of delayed return to play across all calf strain injuries
3. 03MRI findings of the index injury did NOT predict recurrence risk
4. 04Older age increased risk of early recurrence (AHR 1.3, P=.001) and overall recurrence (AHR 1.1, P=.013)
5. 05A prior history of calf muscle strain injury increased overall recurrence risk nearly 7-fold (AHR 6.7, P=.002)

How it was conducted

Design

Case-control study using the AFL Soft Tissue Injury Registry (Level of evidence 3)

Participants

149 MRI-confirmed calf muscle strain injuries from elite Australian Football League players over 4 seasons (2014-2017)

Cases

114 index injuries and 35 recurrent injuries

MRI classification

Two blinded radiologists independently classified injury location, presence and severity of aponeurotic disruption, waviness, edema length, and scar tissue

Primary outcomes

Days to return to play and cumulative incidence of recurrence within 2 seasons

Analysis

Cox proportional hazards regression with adjusted hazard ratios; Kaplan-Meier survival curves

What they found

• Players with severe AD returned to play in 31.3 +/- 12.6 days vs 19.4 +/- 10.8 days for those with no AD (P=.003)
• CMSI with any AD took on average 8.4 days longer to return to play than those without AD (27.8 +/- 15.9 days vs 19.4 +/- 10.8 days; r=0.27; P=.007)
• Running-related mechanism of injury was associated with longer RTP for all CMSI (AHR 0.59; P=.019) and soleus injuries specifically (AHR 0.55; P=.01)
• Presence of AD was associated with longer RTP for soleus injuries (AHR 0.6; P=.025)
• Older age was associated with early recurrence (AHR 1.3; P=.001) and overall recurrence (AHR 1.1; P=.013)
• Prior ankle injury increased early recurrence risk (AHR 3.9; P=.032)
• Prior calf strain history increased overall recurrence risk (AHR 6.7; P=.002) and soleus-specific recurrence (AHR 5.6; P=.005)
• Index injury MRI findings were not associated with recurrence (early: HR 0.99, P=.41; overall: HR 1.01, P=.39)
• 63.2% of early recurrences involved the same muscle, gross position, and anatomical location as the index injury
• Median time to recurrence was 58 days for soleus injuries

Limitations

• Single sport cohort (AFL) limits generalizability to other sports and non-elite populations
• Club medical personnel could not be blinded to MRI findings when managing players, potentially influencing return-to-play decisions
• No comparison with uninjured players was possible as data on non-injured athletes were not collected
• Sample was insufficient for a separate multivariable analysis of gastrocnemius injuries due to small numbers

Why it matters

For patients

Athletes who have had a previous calf strain or are older are at significantly higher risk of re-injury, highlighting the importance of thorough rehabilitation before returning to sport.

For clinicians

MRI aponeurotic disruption and a running mechanism signal longer rehabilitation timelines, but recurrence risk should be assessed primarily through clinical history, not MRI findings of the index injury.

For readers

This is the largest study to date linking specific MRI and clinical factors to calf strain outcomes in elite football, providing a practical framework for prognosis that prioritizes clinical history over imaging for recurrence prediction.