Previous Anterior Cruciate Ligament Injury Compromises Bone and Muscle Strength in Collegiate Athletes

Abstract

A growing body of research has shown that recreationally active individuals have decreased bone and muscle strength following anterior cruciate ligament (ACL) injury and reconstruction; largely attributed to immobility following reconstructive surgery. However, little research has examined musculoskeletal adaption to ACL injury among collegiate athletes. PURPOSE: To examine limb-to-limb differences in muscle and bone strength parameters in collegiate athletes with a history of ACL injury and reconstruction. METHODS: Peripheral quantitative computed tomography (pQCT) and a series of muscle function tests were used to assess bone and muscle strength, respectively, among 12 Division III college athletes (5 males, 7 females; age=20.7 ± 0.5 years) with an ACL injury in the previous five years. Total and cortical bone volumetric density (ToD and CoD), and cortical bone mineral content (CoCnt), bone area (CoA), thickness (CoTh) and estimated bone strength (SSIp), along with muscle cross-sectional area (MCSA) were measured using pQCT at the proximal tibia (66%), patella midline, and distal femur (20%) sites. Muscle function assessment included single-leg hop and isometric manual muscle tests. A Lysholm Knee Scoring Scale was also administered. Both limbs were measured and a leg symmetry index (LSI) was calculated for all assessments. RESULTS: Tibia CoCnt (LSI=97.3%) was lower in the injured limb, along with patella ToD (LSI=89.7%; both p<0.05). At the femur, CoA (LSI= 94.4%) and CoTh (LSI= 94.4%) were lower in the injured limb (both p<0.05). MCSA was lower at the tibia (LSI=96.2%) and femur (LSI= 87.1%) of the injured limb, along with performance on the single leg (LSI= 78.2%) and cross hop (LSI=85.3%) patterns of the hop test (all p<0.05). No limb differences were found for manual muscle tests. CONCLUSIONS: Our results showed less robust bone density and geometry parameters, along with lower muscle strength outcomes in ACL-injured limbs among collegiate athletes up to five years following injury. These differences, however, were less pronounced than deficits previously reported among older, recreational athletes. Future research should investigate the effect of pre-injury health and fitness status in athletes compared to the general population. Supported by University of St. Thomas Young Scholar Grant.