Quadriceps dysfunction (e.g., weakness or atrophy) is often implicated in the increased prevalence of posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR). However, the relationship between quadriceps dysfunction and PTOA development relies on limited insight. To this end, magnetic resonance T1rho relaxation times directly assess cartilage composition, yet the long-term relationship between cartilage composition and quadriceps dysfunction has not yet been explored within a single graft type. Our objectives were to assess cartilage composition using T1rho values 3 years post-ACLR via patellar tendon autograft and to examine associations between quadriceps strength or volume and cartilage composition. Twenty-four individuals with ACLR (male/female = 15/9, age = 22.8 ± 3.6 years, BMI = 23.2 ± 1.9, time since surgery = 3.3 ± 0.9 years) and 24 Controls (male/female = 14/10, age = 22.0 ± 3.1 years, BMI = 23.3 ± 2.6) participated. Linear mixed-effects models assessed T1rho values between ACLR, Contralateral, and Control Limbs. Linear regressions determined associations between quadriceps strength or volume with T1rho in significant regions identified by the linear mixed-effects models. T1rho values in the ACLR limb were 7%–12% longer in the medial and lateral patella, and trochlea compared to Contralateral and/or Control limbs (p = 0.009–0.049), with no associations with strength or volume (p > 0.05). Three years following ACLR via patellar tendon autograft, the patellofemoral joint exhibited compositional changes that were not associated with quadriceps strength or size. Future studies should explore if similar changes occur with other graft types and investigate the role of additional factors known to impact joint health (e.g., walking mechanics).