Isometric quadriceps strength metrics and patient-reported outcomes are commonly used in return to sport assessments in those with anterior cruciate ligament reconstruction (ACLR). Patients may be experiencing clinical knee-related symptoms aggravating enough to seek additional medical care following ACLR. In addition to seeking additional medical care, these patient-reported clinical knee-related symptoms may, also, be influencing function in individuals following ACLR. However, it is unknown if there is an association between these common quadriceps metrics and patient-reported clinical knee-related symptom state.
To determine if meeting isometric quadriceps strength and symmetry criteria is associated with acceptable clinical knee-related symptoms 5–7 months post-ACLR.
We classified individuals 5–7 months post-ACLR based on their isometric ACLR and uninvolved limb quadriceps strength and/or quadriceps strength symmetry. We, also, dichotomized participants based the Englund et al. criteria for unacceptable clinical knee-related symptoms.
Quadriceps strength variables were compared between groups using ANCOVAs and the relative risk of a participant in each quadriceps strength group reporting acceptable clinical knee-related symptoms were determined using binary logistic regression.
One hundred and seventy-three individuals participated in the current study. Isometric quadriceps strength and LSI were significantly different (p<0.001) between quadriceps strength groups. Those categorized as both strong and symmetrical had 1.28 (confidence interval (CI): 0.94, 1.74) and individuals categorized as symmetrical only had 1.29 (CI: 0.97, 1.73) greater relative risk of reporting acceptable clinical knee-related symptoms compared to the neither strong nor symmetrical group.
The majority (85.0%) of individuals recovering from ACLR fail to meet either the clinical quadriceps strength or symmetry criteria 5–7 months post-ACLR. Quadriceps strength and quadriceps strength symmetry are clinically important but may not be a primary determinant of clinical knee-related symptom state within the first 6-months post-ACLR.