Patellofemoral Joint Forces and Stress During Forward Step-up, Lateral Step-up, and Forward Step-down Exercises
Chinkulprasert C, Vachalathiti R, Powers CM. J Orthop Sports Phys Ther. 2011 Apr;41(4):241-8.
When developing exercises programs for patients, clinicians need to select exercises that will best benefit the return of mobility, strength, and function. Throughout the selection process for lower extremity programs, a clinician should use open and closed kinetic chain exercises to help regain strength. Stepping exercises are frequently used for lower extremity programs; especially in rehabilitation protocols associated with ligament reconstruction. However, when we select stepping exercises we should carefully choose exercises that minimize patellofemoral loading and monitor proper technique and exercise tolerance; specifically at the patellofemoral joint. This study looked at patellofemoral joint reaction force and patellofemoral joint stress (force per unit of contact area) with 3 commonly used exercises: 1) forward step up, 2) lateral step up, and 3) forward step down (FSD). Twenty healthy subjects (10 male and 10 female) aged 18 to 35 years were used in the study. The step height was standardized to encourage 45 degrees of flexion. Three dimensional lower extremity kinematics and EMG signals were collected as the participants performed 3 trials of 5 repetitions for each exercise. Patellofemoral loading was determined through biomechanical modeling. Overall the patellofemoral joint reaction force and stress were greater during the FSD than the two other exercises. During all three exercises, patellofemoral joint reaction forces and stresses were greater during the eccentric phase than the concentric phase. 
This study is interesting because it indicates that there is increased patellofemoral joint loading with FSD over the forward and lateral step-up exercises. The increased knee flexion angle with the FSD exercise was the main contributor to the increased patellofemoral joint reaction forces. This data should be taken into consideration when selecting exercises especially since patellofemoral joint stress is hypothesized to be a contributor to patellofemoral symptoms. While it is easy to subjectively monitor the pain tolerance to step up/down exercises, this study gives interesting information that should be utilized for patients that are pain free with these tasks. It is important to keep in mind that this study only included healthy-young adults and it is unclear how much this data applies to patients with knee pain. As clinicians we should ask questions like: Should step-down exercises be avoided with knee post-op patients that have quad tone/strength deficits and may be predisposed to developing patellofemoral pain during the post operative process? Should the age of the patient and/or the degree of degenerative changes to the patellofemoral joint be considered? This is a topic that I have debated with colleagues over the years. This study supports the need for consideration of short and long-term benefits/consequences of performing the stepping exercises. The authors also found that the patellofemoral loading was greater during the eccentric phase than the concentric phases of each exercise. This can assist the clinician in terms of progressing a stepping program when pain is an issue. The data supports focusing on the concentric phase initially and then gradually progressing to the eccentric phase when strength improves and pain is controlled. It would be interesting to hear how clinicians utilize this exercise with their patient populations and if the data of this study is consistent with the level of difficulty and pain tolerance of the 3 exercises in this study.
Written by: Thomas Martin
Reviewed by: Jeffrey Driban