Influence of external load during back squats on knee joint arthrokinematics analyzed by vibroarthrography

The specific influence of heavy external loads during back squats on patellofemoral joint arthrokinematics remains unclear. Therefore, this study aimed to evaluate these effects in vivo using vibroarthrography across a wide range of loads (0-70 kg).

An eight-load, randomized-order, within-subject design was used. Thirty-eight male team sport athletes (age: 22.0 ± 1.1 years, body mass: 82.8 ± 10.1 kg) performed back squats under eight external load conditions (0-70 kg) with 1-min rests between tests. The arthrokinematic quality of the patellofemoral joint was assessed using an accelerometer sensor placed 1 cm above the apex of the patella.

The results revealed that the vibroarthrographic signal increased in an almost linear manner with an increasing knee load during the squat. This increase was statistically significant for loads equal to or greater than 40 kg (P < 0.001) for the signal variability parameters (VMS and R4) and for loads equal to or greater than 20 kg (P ≤ 0.007) for the frequency parameters (P1 and P2). Analyzing the median values, the VMS parameter increased by 150 %, R4 by 23 %, P1 by 135 %, and P2 by 140 % at the maximum load of 70 kg compared with the squat without a load.

The vibroarthrographic signal level steadily increases with increasing knee load during squats, seemingly associated with higher contact stress and kinetic friction of articular surfaces. This linear phenomenon is visible across the entire range of applied loads. Consequently, athletes and coaches should consider that progressively increasing loads may contribute to joint wear over time.