Marked asymmetry in vertical force (but not contact times) during running in ACL reconstructed athletes <9 months post-surgery despite meeting functional criteria for return to sport.

OBJECTIVES: Compare maximum plantar force (Fmax) during running in soccer players following anterior cruciate ligament reconstruction (ACLR) as they pass return to sport (RTS) criteria.

DESIGN: Case control study.

METHODS: Soccer players after ACLR (n=16) and matched healthy controls (n=16) ran on a treadmill at 12, 14 and 16km/h while plantar loading data was measured using an in-shoe pressure system (Pedar-X, Novel). Fmax and contact time of the injured and uninjured limbs in athletes <9months post-ACLR and those ≥9months ACLR were compared to healthy players (no ACLR).

RESULTS: Significant differences with large effect sizes in Fmax asymmetry were seen at all running speeds for the athletes <9months ACLR compared to those ≥9months, and the healthy subjects. Fmax difference peaked at 16km/h; 32±11%BW in <9months ACLR group compared to 6±5%BW in ≥9months group; ES=1.67, p<0.01. There was a non-significant trend for increasing asymmetry with increasing speed for subjects who were <9months after ACLR while the reverse was true for those ≥9 months and the healthy subjects.

CONCLUSIONS: Relatively large unloading of the ACLR limb (but not differences in contact times) are seen during running for athletes <9months post-ACLR despite having completed functional criteria required to permit RTS training. These asymmetries appear to slightly increase with increasing speed, and the reverse is true for healthy controls and those ≥9months after ACLR surgery.