Articular Cartilage Arthrokinematics and Compositional Measurements With qMRI 1 to 2 Years After ACL Reconstruction With Meniscal Surgery

BACKGROUND: Posttraumatic osteoarthritis (PTOA) often follows anterior cruciate ligament reconstruction (ACLR), especially when combined with meniscal surgery (ACLR+M). The mechanisms underlying development of PTOA remain unclear, including the early mechanical and compositional changes after surgery that potentially lead to irreversible cartilage degeneration. PURPOSE: To investigate the early effects of ACLR+M on joint arthrokinematics using dual-fluoroscopy with model-based tracking and cartilage composition using quantitative magnetic resonance imaging (qMRI). STUDY DESIGN: Controlled laboratory study. METHODS: Twelve participants who underwent ACLR+M were assessed 1 to 2 years after surgery. Dual-fluoroscopy with model-based tracking was used to quantify 6 degrees of freedom joint movements during walking and jogging. Arthrokinematics were assessed at 6% and 3% of the gait cycle for walk and jog, respectively, using magnetic resonance-based cartilage models. qMRI measured T1ρ relaxation times in the weightbearing tibial and femoral cartilage of both medial and lateral compartments. RESULTS: Reconstructed knees showed increased anterior and lateral tibial translation during walking and jogging, larger abduction rotation during jogging, and a posterior shift of the tibiofemoral contact points on the tibia during walking relative to contralateral knees. The cartilage contact overlap area was increased in the medial compartment during walking in the reconstructed knee compared with the contralateral knee. Higher T1ρ relaxation times were observed in both medial and lateral femoral cartilages of the reconstructed knee compared with the contralateral knee. No correlation was found between reconstructed side-to-normal side differences in arthrokinematics and T1ρ relaxation times. CONCLUSION: These findings indicate early side-to-side differences in arthrokinematics and cartilage composition 1 to 2 years after ACLR with meniscal surgery, but patients with bigger side-to-side differences in arthrokinematics did not demonstrate bigger side-to-side differences in cartilage composition. CLINICAL RELEVANCE: Understanding mechanical and compositional differences after surgery, as well as the relationship between mechanics and composition, provides insight into their roles in PTOA initiation. This study underscores how ACLR with meniscal surgery affects tibiofemoral joint arthrokinematics and cartilage composition via qMRI. Results may provide insights into the early stages of PTOA and could inform postoperative strategies and/or targets for rehabilitation.