Effects of anterior cruciate ligament reconstruction on patellofemoral joint stress and lower extremity biomechanics at 12 weeks post-surgery and at time of return to sport in adolescent females.

BACKGROUND: The purpose of this study was to examine kinematic and kinetic differences associated with patellofemoral pain after anterior cruciate ligament reconstruction between limbs at 12-week post-surgery and at time of return to sport. METHOD: Twenty-four adolescent females completed 5 consecutive single leg squats on each limb at 12-weeks post-surgery and again during their RTS assessment. Peak knee extension moment, peak hip adduction angle, and patellofemoral joint stress at 45 degrees of knee flexion were calculated. Separate two by two repeated measures ANOVA were performed. FINDINGS: There was a significant interaction (limb × time) for knee extension moment (p < 0.001). Surgical limb knee extension moment was significantly less than the non-surgical limb at return to sport (p < 0.001). At 12-weeks the surgical limb was significantly less than non-surgical limb (p < 0.001), additionally the surgical limb was significantly greater at time of return to sport than at 12 weeks (p < 0.001). There was a significant main effect of limb for hip adduction angle (p = 0.002). Surgical limb was significantly greater than non-surgical limb (Surgical = 9.84 (SE 1.53) degree, non-surgical = 4.79 (SE 1.01) degree). There was also a main effect of time and limb for patellofemoral joint stress. Return to sport was significantly greater than 12 weeks and the surgical limb was significantly less than non-surgical limb (Surgical = 4.93 (SE 0325) MPa, Nonsurgical = 5.29 (SE 0.30) MPa). INTERPRETATION: The surgical limb of participants following ACL-R demonstrated variables that have been associated with the development of patellofemoral pain.

Peripheral joint cooling increases spinal reflex excitability and serum norepinephrine.

To understand better how reflex excitability is altered with peripheral joint cooling, the authors set out to determine whether a cryotherapy treatment applied to the ankle would increase plasma norepinephrine and result in a heightened H:M ratio. Twenty-two adults were admitted to the hospital on two occasions. During one admission, subjects had ice applied to their ankle and in the other admission a bag of room temperature marbles was applied. Soleus Hmax, Mmax, H:M ratio, and plasma norepinephrine were recorded at baseline as well as immediately, 10, and 20 min post application, and 10 and 20 min post removal. Norepinephrine was greater immediately and 10 min post ice application (p < .05). Hmax, Mmax, and the H:M ratio were greater at 10 and 20 min post application and at 10 and 20 min post removal (p < .05). Elevated plasma norepinephrine suggests that peripheral cooling results in release of neurotransmitters from the central nervous system. Joint cooling has both peripheral and central effects.