Sports Medicine Research: In the Lab & In the Field: Guest Post: Patellofemoral Loading During 3 Common Exercises (Sports Med Res)


Friday, April 15, 2011

Guest Post: Patellofemoral Loading During 3 Common Exercises

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


Tommy Nowakowski said...

Great post Thomas, I really like the front step up and lateral step up exercise in most of my lower extremity rehabilitations especially in those with patellofemoral issues. I use them in later stages after beginning to establish (or re-establish) hip control. I'm not a big fan of step downs in too many cases. I do use a step down variation similar to what would amount to a closed chain short arc quad for patellar tendonitis cases. I think a traditional step down exercise carries too much risk to reward in performing the exercise because of the load stressing the patellofemoral joint as stated in the post. To me it is very difficult to have an athlete/patient perform that exercise without the individual allowing their knee to translate anteriorly in comparison to the foot which I feel causes that undue stress to the patella. With that said I do use the front step down as an evaluation tool in cases of patellofemoral complaints to assess hip control. Although it is not completely functional in nature, in my own head, I believe it gives me an indication of how the affected extremity is controlled when landing solely on that leg during running without making that kid continue to run...just my two cents!

Tom Martin said...

Thanks for the comments Tommy.

This is a very interesting topic. This study was of significance to me because it gave data in regards to patellofemoral loading with exercises used frequently with LE injury/dysfunction.

The step down exercise is represented in studies and protocols. But I have a hard time training an athlete/patient in a position that we try to avoid (knee over foot position). The risk-reward comment you made is how I look at the situation.

Realizing that descending stairs is something done with all ADLs, I try to have patients/athletes control the eccentric phase of the LSU and FSU exercises. Hoping for carryover with stepping down.

Sometimes I wonder if I am respecting the patellofemoral joint too much (by avoiding this exercise even when pain is not an issue)but it is of my opinion that once this joint is an issue it is very difficult to get back to baseline.

Again, thanks for the comments.

Tommy Nowakowski said...

Tom...I very much agree with you. What are the LSU and FSU exercises you speak of???

Tom Martin said...

Sorry Tommy

The Forward step up and Lateral step up.

I really try to have them control the eccentric phase of the exercise, instead of just dropping from the step.
Work the eccentric but keep with better positioning in terms of knee over foot.

Sorry for the abbreviations.

Mark Ramsey said...

We use 3", 6" and 9" step downs frequently for assessment and ther ex purposes as part of a progression of course. It's very revealing to a patient when they see how good they are on a 9" step up yet struggle on a 3" step down. We respect pain and they must be able to perform it with good form and painfree before we incorporate into their program.

Tom Martin said...

Thanks for the comments Mark

You obviously have a safe protocol for using the step down exercise. Going from a low grade to a high grade step and assessing quality and pain will benefit the patient in terms of minimizing patellofemoral pain.

I do think it is a valuable tool in the assessment process. From a pain and biomechanical standpoint,a clinician can get some valuable information.

When I look at using the step down exercise it comes down to the increased knee flexion angle and patellofemoral loading.
Looking more at patellofemoral joint reaction force and stress than patient tolerance/pain is how I judge using this as an exercise.

Again, thanks for the comments on how you utilize the step down.

Mark Ramsey said...

How would we know where the cutoff for an exercise is based on PF joint reaction force?
And why would that be a better indicator than pain and form?

Jeffrey B. Driban, PhD, ATC, CSCS said...

Mark & Tom:

This is an interesting discussion and I couldn't resist briefly jumping in. I think the recent post describing the single-leg squat test is useful when we discuss the diagnostic potential for these step up/downs. It would be helpful if studies determined which test (e.g., single-leg squat, step down from different heights) is the most effective. It will also be interesting if the authors of that study follow-up on the idea that inexperienced clinicians don't do those evaluations as well as experienced clinicians. Then the question also becomes: how can we improve our training/teaching to help inexperienced clinicians become more proficient in these evaluations.

From a therapeutic exercise point of view I would suggest that we should not look at the current study for a cut off in PF joint loading but rather use this data to qualitatively rank the exercises. For example, which exercise leads to the most loading and which exercise to the least loading. I would prefer to start my exercise progression with the exercise with the lowest PF loading and then gradually increase the exercises as tolerated. Each patient at each visit will likely have a different cutoff for PF joint forces that they will tolerate. At the end of the day, pain and form are important determinants for progressing through the exercises with different PF loads (this is similar to Tom's first sentence in his previous comment). As for Tom's last comment: If I have two functional exercises that elicit equivalent muscular activation and the person is symptom free with both exercises I would pick the exercise with the lower PF loads. My little addition is that proper form is really key here. An exercise with low PF loading can easily have higher loading when performed incorrectly.

That's my very long two cents. I hope it helps.

Tom Martin said...

Thanks Jeff and Mark

Your last comment is a great one and has posed many discussions with colleagues over the years.
Many agree totally with your stance and utilize the same rationale. And I respect the thought process when using that exercise.
I agree with the ranking of exercises when looking at patellofemoreal loading. I am a big supporter that concept throughout exercise progression. (Building a good base than gradually increasing the challenge to get a good outcome)

I guess the question comes down to what Mark said, where is the cutoff??
When looking at the cutoff in terms of this concept I look at everything from the patient evaluation/goals to the exercises chosen to accomplish the task. When selecting the exercises is where I like to let the Reasearch/my personal experience/patient evaluation come together. With this particular exercise I avoid certain positions, like the knee over foot position that occurs with the step down. When looking at step training for the LE, the eccentric phase of the step up (forward and lateral) is the max patellofemoral load I like to place on a knee.
That being said, I think every clinician will have their own cut off based on their experience with certain exercises.
In the end, when attention is paid to pain/technique/patient needs/research we are accomplishing our goal of providing quality care and the outcomes will determine further use.
Mark, I know this probably doesn't answer your question completely but I hope this clears it up.

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