Patients recovering from ACL reconstruction often want to know what influences how strong their leg will feel afterwards. One possible factor is muscle fibre composition in the hamstring, especially when a hamstring tendon graft is used for surgery. A 2025 study co-authored by Dr Jobe Shatrov looked at whether this could predict strength recovery after ACL reconstruction.

The answer was no.

Why this question matters

ACL reconstruction is not just about reconstructing the ligament. A good outcome also depends on:

• restoring muscle strength

• regaining movement quality

• returning confidence in the limb

• progressing safely back to sport or activity

If surgeons or physiotherapists could identify biological factors that predicted recovery, it might help guide rehabilitation. This study tested whether hamstring muscle composition was one of those factors.

What the study set out to test

The researchers followed patients undergoing ACL reconstruction with a hamstring tendon autograft. They looked at the composition of the semitendinosus muscle and compared that with isokinetic strength recovery at six months.

The main question was whether the internal make-up of the hamstring could help predict how much strength the operated leg would recover compared with the non-operated side.

What the study found

The study found no statistical relationship between muscle composition and six-month strength recovery. In other words, muscle fibre type did not predict how strong patients would be at that point in rehabilitation.

This is useful because it suggests that routine assessment of muscle fibre composition does not add practical value in predicting recovery after this type of ACL surgery.

What this means for patients

For patients, this is reassuring. It means recovery does not appear to be predetermined by a hidden biological characteristic in the hamstring. Instead, the more important factors are likely to remain the practical ones:

• good rehabilitation

• consistency with exercises

• appropriate progression

• time and patience

This shifts the focus back to the things patients and clinicians can actually work on.

What it means in practice

This study supports a rehabilitation-first mindset. Rather than worrying about muscle fibre type, clinicians can continue to focus on:

• swelling control

• range of motion

• quadriceps and hamstring strength

• balance and movement control

• clear progression through milestones

It also helps simplify patient counselling, because muscle composition testing does not appear necessary for routine recovery planning.

Key takeaways

• Muscle fibre composition did not predict six-month strength recovery after ACL reconstruction with hamstring grafts.

• Recovery is more likely to depend on rehabilitation quality and progression.

• The findings support a practical, rehab-focused approach rather than biological profiling.

Read the full paper: https://www.sciencedirect.com/science/article/pii/S1877056824004092