Purpose: To investigate strength and functional symmetry during common tests in patients after anterior cruciate ligament reconstruction (ACLR), and its association with post-operative rehabilitation.
Methods: At a median 11.0 months post-surgery (range 10-14), 111 ACLR patients were assessed. A rehabilitation grading tool was employed to evaluate the duration and supervision of rehabilitation, as well as whether structured jumping, landing and agility exercises were undertaken. Patients completed the Noyes Activity Score (NSARS), maximal isokinetic knee extensor and flexor strength assessment, and a 4-hop test battery. Limb Symmetry Indices (LSIs) were calculated, presented for the entire group and also stratified by activity level. ANOVA evaluated differences between the operated and unaffected limbs across all tests. Correlations were undertaken to assess the relationship between post-operative rehabilitation and objective test LSIs.
Results: The unaffected limb was significantly better (p < 0.0001) than the operated limb for all tests. Only 52-61 patients (47-55%) demonstrated LSIs ≥ 90% for each of the hop tests. Only 34 (30.6%) and 61 (55.0%) patients were ≥ 90% LSI for peak quadriceps and hamstring strength, respectively. Specifically in patients actively participating in jumping, pivoting, cutting, twisting and/or turning sports, 21 patients (36.8%) still demonstrated an LSI < 90% for the single hop for distance, with 37 patients (65.0%) at < 90% for peak knee extension strength. Rehabilitation was significantly associated with the LSIs for all tests.
Conclusion: Rehabilitation was significantly correlated with limb symmetry, and lower limb symmetry was below recommended criterion for many community-level ACLR patients, including those already engaging in riskier activities. It is clear that many patients are not undertaking the rehabilitation required to address post-operative strength and functional deficits, and are being cleared to return to sport (or are returning on their own accord) without appropriate evaluation and further guidance.
Level of evidence: IV.
Keywords: Anterior cruciate ligament injury; Limb symmetry index; Lower limb strength; Rehabilitation; Single leg hop test.