Effects of Hip and Knee Exercises on Knee Pain in Young Adult Females With Long-standing Patellofemoral Pain
Condition: Patellofemoral Pain Syndrome
MeSH terms: Patellofemoral Pain Syndrome
Study type: Interventional

Summary: 
      Patellofemoral pain (PFP) is highly prevalent in both adolescent and adult populations and as
      much as 91% of those affected experience ongoing knee pain for up to 20 years after the
      initial diagnosis.

      Exercise-based treatment focusing on strengthening the muscles around the hip and knee is
      usually effective when treating patient with PFP. However, this approach has proven
      ineffective in a subgroup of females who have suffered from PFP for multiple years.

      This group was found to have a significantly lower tolerance for pressure stimuli compared to
      healthy controls. This indicating that central mechanisms within the nervous system rather
      than the problem being the knee itself.

      Exercising a non-painful muscle distant to a painful part of the body has previously been
      effective in deceasing pain in affected area. This mechanism has been investigated in
      patients with long-standing musculoskeletal pain as well as healthy populations.

      Related research has suggested that a possible link between patients perception of painful
      stimuli an the pain-reducing effect of exercise exists. As such, patients witch experienced a
      pain reducing effect of exercise was found to be able to tolerate more pain than before the
      intervention.

      The aim of this study is to assess if exercising a distant non-painful muscle around the hip
      has a larger acute pain-reducing effect on knee pain compared to knee specific exercises in
      female patients with long-standing PFP.
    

Detailed description: 
      Background: Patellofemoral pain (PFP) has a high prevalence in both adolescent and adult
      populations (7% and 15%) and as much as 91% of those affected experience ongoing knee pain
      for up to 20 years after the initial diagnosis. Exercise-based treatment focusing on
      strengthening the muscles around the hip and knee is usually effective when treating patient
      with PFP. However, this approach has proven ineffective in a subgroup of females with
      long-standing PFP. This group was found to have altered condition pain modulation indicating
      facilitated central mechanisms. A localized analgesic effect by exercising a distant
      non-painful muscle has been observed previously in patients with long-standing
      musculoskeletal pain. This is known as exercise induced hypoalgesia. In relation, an
      increased condition pain modulation was found to be a predictor for an increase in the effect
      of exercise induced hypoalgesia, indicating a link between the two mechanisms. The aim of
      this study is to assess if exercising a distant non-painful muscle around the hip has a
      larger acute analgesic effect on localized knee pain compared to knee specific exercises in
      female patients with long-standing PFP.

      Study design: This study is a randomized, controlled, participant and assessor blinded
      crossover study. The study will be conducted at the Research Unit of General Practice in
      Aalborg. Reporting of the study will follow the CONSORT guidelines for randomized trials of
      Non-pharmacologic Treatment.

      Method: Thirty women between the age of 20 and 25 with current knee pain which they have
      experienced ongoing or recurrent for a duration of 5 years will be randomized to either a
      knee or hip specific resistance exercise as their first intervention. After a washout period
      of 15 minutes, the participant will perform the other exercise. The participants will undergo
      a test-procedure before the first exercise, between the exercises and after the final
      exercise. The test-procedure consist of handheld pressure algometry and cuff pressure
      algometry assessing pain pressure threshold, pain detection threshold and pain tolerance
      threshold. Condition pain modulation and temporal summation of pain will be assessed by cuff
      algometry. In order to assess knee pain in relation to the exercises, the participants will
      be asked to rate their knee pain before and after each exercise set. The primary outcome will
      be pain pressure threshold assessed by handheld pressure algometry at the center of patella
      of the test limb.

      Recruitment: A random sample of participants from the APA2011 cohort who experience ongoing
      PFP in 2016 will be invited to participate in this study. The participants will be contacted
      by telephone and invited to participate in the study. Verbal information regarding the study
      will be provided over the phone and written material will be send by e-mail. In case the
      cohort provide an insufficient number of participants, patients from general practice will be
      sought out and invited to participate. This process will be done in collaboration with
      general practice clinics in the area. If the combination of the above-mentioned strategies
      does not provides the required number of participants, online social-medias like Facebook and
      Twitter will be used as a mean to obtain a sufficient number of participants.

      Allocation sequence: The participants will be randomized to do either sitting knee extension
      or sidelying hip abduction first. A computer generated allocation sequence will be conducted
      at www.random.org by an independent researcher. This individual will put slips of paper,
      which says either "Hip" or "Knee" into opaque sealed envelopes. The envelopes will be marked
      with sequential numbers. When the first participant have underwent the baseline testing he or
      she will be assigned the ID number 1 (ID1). After completing the baseline test this
      participant will proceed to the exercise room where the exercise instructor will be waiting.
      The exercise instructor will then select the envelope marked "ID1" and note if the
      participant was assigned to the hip or knee exercise as the first exercise.

      Familiarization session: Before each exercise, the load at which the participants can do
      exactly 12 repetitions will be established by using elastic band with different elastic
      abilities. This will also work as a familiarization session where the participants can get to
      know the exercises. For the familiarization session, a black elastic band will be used as
      default for the sitting knee extension exercise, whereas a yellow elastic band will be used
      in the sidelying hip abduction exercise. If the participants are capable of performing more
      or less than 10-12 repetitions with the default elastic band, the length or color will be
      changed to ensure the participants exercise at 12RM.

      Precautions: Participants will be asked to withstand from caffeine, alcohol, nicotine and
      physically exhausting activities for up to 24 hours before undertaking the study protocol as
      these have been shown to have a dampening effect on pain. Due to the nature of the study,
      participants are encouraged to withstand from taking any analgesics on the day for undergoing
      the study protocol.

      Data analysis: A preliminary analysis to see if order of exercise has an effect on the
      results will be conducted. To investigate if there is any statistically significant
      difference in PPT, pain detection threshold (PDT) and pain tolerance threshold (PTT) and VAS
      scores measured at the three time-points, a repeated measure analysis of variance (ANOVA)
      will be undertaken if data is found to be normally distributed. If data is not normally
      distributed the Kruskal-Wallis test will applied instead. This data will be presented with a
      mean, a standard deviation, an f-value and a p-value. For the PPT, PDT and PTT a mean
      difference of 50 kPa is considered to be clinically relevant.

      In addition, the association between knee pain intensity at baseline testing and EIH response
      for hip versus knee exercises will be investigated. By doing this test it will be possible to
      assess if those with greater knee pain intensity has a larger EIH response from hip exercises
      compared to knee exercises.

      To assess flare up in pain during exercise the mean change in numeric pain ratings from start
      to finish of each set within each exercise (hip or knee) will be calculated.

      To investigate if there is any correlation between handled PPT measured at the three sites
      (center of patella on the test limb, the belly of the m. tibialis anterior muscle og the test
      limb and the epicondyle of the contralateral elbow) a test for correlation will be conducted.

      In order to examine if the flare up in pain during exercise behave the same way as TSP, a
      test for correlation between these two variables will conducted.

      Sample size: A group of 10 healthy subjects volunteered to participate in a pilot study prior
      to recruitment of the current study. Data regarding handheld PPT measured at the center of
      patella was used to calculate the sample size required to power the study. The mean
      difference between handheld PPT after hip exercise and after knee exercise within the group
      was 44 kPa with a corresponding standard deviation of 80 kPa. These data was used in a
      two-sided power analysis for two paired means which was conducted in STATA. With a
      significant level of 0.05 and the power set to 0.8, a minimum of 28 participants would be
      required to power the study. However, 30 participants will be included in order to insure the
      study is adequately power in case of missing data due to system malfunction or if the effects
      size turns out to be lower than the anticipated 0.55.

      This randomized study is embedded within a larger cross-sectional study which is approved by
      the ethical committee under the same approval number (N-20160058). This can be accessed on
      clinicaltrials.gov under the title "Pain mechanisms in Young Adolescent Females With
      Longstanding Patellofemoral Pain" with Dr. Sinead Holden as the primary investigator.
    

Intervention name(s): Hip specific resistance exercise; Knee specific resistance exercise
Intervention type(s): Other; Other
Intervention description(s): Hip specific resistance exercise; Knee specific resistance exercise
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: After providing informed consent the participants will determine which is their most painful knee. This limb will be marked and it will serve as the test limb throughout the study protocol. At the first step of the protocol the participants will be baseline tested with handheld and cuff pressure algometer. Secondly, participants will be randomized to either a hip or a knee exercise. Thirdly, participants will undergo the testing-procedure for the second time. Fourthly, participants will perform exercise focusing on the other joint (hip or knee). Finally, participants will undergo the testing-procedure for the last time. In order to avoid any carryover effect from the testing procedure, there will be at least 15-minutes between each of the three test sessions.
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Patellofemoral pain; PFP; PFPS