An analysis by researchers from La Trobe Sport and Exercise Medicine Research Centre has shown that, following anterior cruciate ligament (ACL) injury and reconstruction, there was no widespread or substantial weakness of the hip or lower-leg muscles in the injured group compared to an uninjured control group and to the uninjured contralateral limb.

The systematic review and meta-analysis included 28 studies, of which 16 examined hip abduction, 12 examined hip extension, and seven examined hip external rotation strength.

Data came from studies from 12 countries across Europe, North and South America, Asia, Oceania and the Middle East, with a total of 1103 ACL-injured and 1145 uninjured controls, and a mean age of 19 to 38 years in the ACL group.

The majority of the studies measured strength within 12 months of surgery, while three measured it more than 36 months post-surgery.

Strength was tested using either a hand-held dynamometer or with computerised isokinetic dynamometers to measure slow-speed concentric or eccentric strength.

The analysis found no evidence for a difference in strength for hip abduction, hip internal rotation, hip extension, hip flexion, plantarflexion or dorsiflexion between ACL-injured limbs and uninjured controls.

For hip adduction, the ACL-injured limb was 24 per cent stronger than for uninjured controls, and for hip external rotation, the ACL-injured limb strength was 12 per cent lower than in uninjured controls, though this result was only seen in two studies.

The researchers concluded that, through their meta-analysis, there was no evidence to support the notion that widespread hip or lower-leg- muscle weakness exists after ACL injury, when compared to uninjured control groups or to the uninjured contralateral limb.

However, they acknowledged that the certainty of evidence was low for all outcomes due to the small number of included studies.

The researchers stressed the importance of individual assessment of hip and lower-leg strength, given that it is still unclear whether no post-injury weakness will arise or if deficits resolve following rehabilitation.

Access the research paper here.