Intratendinous hamstring injuries: sequential MRIs as a tool to reduce the risk of reinjury in elite sport

Key points

1. 01All three players had grade 2c or 3c hamstring injuries (British Athletics Muscle Injury Classification) with intramuscular tendon involvement confirmed on MRI
2. 02Clinical signs and symptoms improved faster than tendon healing on MRI, meaning relying on clinical markers alone risked premature progression to high-load activity
3. 03Serial MRI showed a consistent pattern: initial hyperintense (bright) tendon signal, followed by progressive darkening and reduction in thickness as the tendon healed
4. 04End-stage rehabilitation (high-speed running, accelerations, match drills) was withheld until MRI showed a hypointense (dark), continuous tendon signal similar to the uninjured side
5. 05All three athletes returned to full training and play without reinjury; return-to-play times ranged from approximately 6 to 12 weeks

How it was conducted

Design

Case series of 3 elite Premier League footballers with intratendinous hamstring injuries

Participants

Three male professional footballers (ages 18, 26, and 27) with acute BAMIC grade 2c or 3c hamstring injuries

Injury locations

Proximal long head of biceps femoris (cases 1 and 3); distal long head and short head of biceps femoris at T-junction (case 2)

Intervention

Initial MRI within 24 hours, followed by serial MRI scans every 7-14 days or every 2-4 weeks depending on injury severity; rehabilitation progression gated partly on MRI tendon signal appearance

Primary outcome

MRI appearance of tendon healing over time and successful return to play without reinjury

What they found

• Case 1: initial MRI (24 h) showed oedema 13x3 mm axially and 17.5 cm craniocaudally with tendon split; normal hypointense tendon signal returned at 70 days; return to play at 84 days with no recurrence
• Case 2: initial MRI showed disruption of >50% of the T-junction tendon and a 6 cm longitudinal split; tendon appeared near-normal at 70 days; full training resumed at 84 days with no recurrence
• Case 3: initial MRI showed a longitudinal intratendinous split in posterior fibres; tendon appeared continuous with near-normal hypointense signal at 32 days; return to full training at 6 weeks (~42 days) with no recurrence
• In case 3, clinical and on-field performance markers at day 17 would traditionally have triggered end-stage rehabilitation, but MRI still showed a gap in the tendon, leading the team to delay progression
• Tendon remodelling involving increased type I collagen synthesis and restoration of normal longitudinal alignment does not begin until at least 6 weeks after injury and can take many months to mature

Limitations

• Only 3 cases reported; no control group, so it is impossible to attribute the absence of reinjury specifically to the MRI-guided protocol
• All athletes were elite Premier League footballers with access to frequent MRI; findings may not generalise to lower-resource settings
• No quantitative MRI metrics were used; tendon healing was assessed visually by radiologists, which may introduce subjectivity
• RTP decisions incorporated multiple clinical and performance factors alongside MRI, making it impossible to isolate the contribution of serial MRI alone

Why it matters

For patients

Athletes with a significant hamstring tendon injury can expect a longer recovery than a simple muscle strain, and clinical symptoms alone may underestimate how much healing remains, so imaging-guided rehabilitation may reduce the risk of going back too soon.

For clinicians

Sequential MRI to confirm normalisation of tendon signal before advancing to high-speed, high-load drills is a feasible strategy in resource-rich environments and may provide an objective safety gate that clinical examination cannot offer.

For readers

This case series provides proof-of-concept that intratendinous hamstring healing follows a visible, consistent MRI trajectory, supporting larger prospective studies to validate MRI-gated return-to-play criteria.