Patellofemoral contact forces after ACL reconstruction: A longitudinal study.

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• Osteoarthritis (OA) is a frequent complication following anterior cruciate ligament reconstruction (ACLR).
• Patellofemoral OA is as common as tibiofemoral OA post-ACLR, yet its development mechanisms remain under-explored.
• Biomechanical alterations are hypothesized to drive post-traumatic knee OA, but patellofemoral joint loading data post-ACLR is conflicting and limited.

Purpose of the Study:

• To investigate patellofemoral contact forces throughout the gait cycle at 3, 6, and 24 months after ACLR.
• To compare patellofemoral loading between the involved and uninvolved limbs over time.
• To explore potential biomechanical mechanisms contributing to patellofemoral OA post-ACLR.

Main Methods:

• Utilized a validated, subject-specific, EMG-driven neuromusculoskeletal model to calculate muscle forces.
• Determined patellofemoral contact forces during level walking across the entire stance phase.
• Employed statistical parametric mapping to compare forces between limbs and time points.

Main Results:

• The involved limb exhibited significant patellofemoral underloading at 3 and 6 months post-ACLR compared to the uninvolved limb.
• This underloading resolved by 24 months post-ACLR.
• Both limbs showed increased loading from 3 to 6 months, with the uninvolved limb's load decreasing by 24 months.

Conclusions:

• Early post-ACLR, the involved limb experiences reduced patellofemoral joint loading during walking.
• This early underloading may be a critical factor in the development of patellofemoral osteoarthritis after ACLR.
• Longitudinal assessment reveals dynamic changes in joint loading patterns post-ACLR.