Knee arthroscopy and exercise versus exercise only for chronic patellofemoral pain syndrome: a randomized controlled trial

Orthopedic surgeons identified consecutive female or male PFPS patients who had been admitted to either the ORTON Orthopaedic Hospital, Helsinki, or one of the outpatient clinics of the public hospitals of the Hospital District of Helsinki and Uusimaa between May 2003 and February 2005. According to our study protocol 56 patients were needed to detect a clinically significant difference between the outcomes of the groups studied. All of the patients who fulfilled the first-stage selection criteria (Table 1) and gave their preliminary consent to participate in the study attended a structured clinical interview and examination held in the ORTON Orthopaedic Hospital and carried out by an experienced orthopedic surgeon (DS) who was not involved in the treatment of these patients. The patients also answered a structured questionnaire. If the patient did not fulfill the final (second stage) inclusion criteria (Table 1) they were excluded. On the basis of the orthopedic surgeon's examination and knee X-ray findings four patients did not fulfill the final inclusion criteria and were excluded from the study. Three of them had symptoms and signs of meniscal injury and one patient had a disabling general illness. Furthermore, one patient refused to participate before randomization. Among patients with bilateral knee symptoms, the knee with the more severe symptoms was included in the study. All of the 56 patients who fulfilled the final inclusion criteria signed an informed consent immediately after the clinical examination and before randomization.

The patients were randomized into two treatment groups: an arthroscopy group, which was treated with knee arthroscopy and 8-week home exercise program, and a control group, which was treated with the same 8-week home exercise program only (Figure 1). The randomization process was carried out using a computer-generated randomization list stratified by gender. Sealed, sequentially numbered envelopes containing information on the treatment group were prepared and given to the assisting nurse, who opened the envelopes in numerical order after recruitment so that concealment of allocation was successful in all cases.

The 8-week home exercise program (see Additional File 1) was started 3 weeks after randomization in all patients (2 weeks after arthroscopy in the arthroscopy group). At the first visit an experienced physiotherapist gave instruction individually on lower-limb muscle strengthening and stretching exercises to be performed daily during the first four weeks at home. The approximate duration of each session was 30 min. The second visit was during the third week from the beginning of the exercise period. For the resisted knee extension and flexion exercises in the second part of the program, all of the patients were given a rubber sling to be used around the ankle. Again, the patients were instructed to repeat the prescribed exercises daily. They were instructed to avoid symptom-producing activities during the intervention. The duration of each daily home exercise session was approximately 30 min.

All of the patients who were randomized into the arthroscopy group received arthroscopy; however, one of them refused to continue treatment thereafter. Arthroscopy was performed one week after randomization by one of the two experienced knee orthopedic surgeons (AH, JS). All of the knee compartments were examined systematically and pathological findings were recorded. The stage of cartilage lesions in the patellofemoral joint was recorded on a standard form according to the Outerbridge [7] classification. During arthroscopy the following procedures were performed, if justified on the basis of the arthroscopic findings and according to our pre-determined guidelines, which followed generally accepted recommendations [2]: resection of inflamed/scarred medial plicae, abrasion of chondral lesions and shaving of excessive and inflamed synovium. Minor corrections of the patellofemoral articulation were performed, such as lateral capsular discision in the case of clear lateral patellar subluxation in the beginning of knee flexion. Moreover, possible meniscal tears were treated. These patients remained in the study group and they participated in the standardized training protocol. One patient, however, was unable to start the exercise program at 2 weeks following the arthroscopy because of pain, and the start of her training was adjusted individually.

Outcome measures were collected using self-administered questionnaires. This data collection was organized by the study coordinator (JAK). As the coordinator did not have any presuppositions as to which of the groups would show better results and because he was not a treatment provider, the data collector was not, for practical reasons, blinded to the treatment groups. The measurements were completed before randomization, immediately after the end of home training period and 9 months after randomization. At each time point the patients filled in the questionnaire alone in a quiet room. The patient-completed questionnaire was then checked by the study coordinator and missing items, if any, were answered. The 24-month evaluation was conducted using a postal questionnaire. The primary outcome measure was the Kujala score (see Additional File 2) [8], also known as the anterior knee pain score [9], which is a 13-item questionnaire including different items on pain related to functioning and activities. The categories within each item are weighted and item scores summed to provide an overall index scored from 0 to 100 where the maximum score of 100 represents no disability. Other investigators have shown that the questionnaire is a reliable, valid and responsive outcome measure for PFPS [9], patients have described it as easy to understand and as depicting the symptoms well [10], and the score has been used widely in evaluating patellofemoral disorders in scientific studies. According to Crossley et al [9] a clinically significant improvement is deemed to have occurred when the patient's score shows an increase of around 8–10 points.

As secondary outcome measures we used three 10-cm visual analog scales (VASs) to assess activity-related pain. Participants assessed the maximum pain they had felt during the previous 2 days when ascending stairs, descending stairs and standing up from a sitting position. Also, a global rating of change between baseline and follow-up (overall assessment) was evaluated with an additional six-point scale: 1, asymptomatic knee, to 6, marked worsening. The scale was later dichotomized and analyzed as follows: (1) marked worsening, moderate worsening or no change from baseline versus (2) moderate improvement, marked improvement or asymptomatic knee.

The patients kept a diary during the therapy intervention. The patients calculated the weekly frequency with which they had followed the exercise protocol. The diary also included questions on pain and discomfort (VAS), possible complications and use of drugs as well as other healthcare services and treatments not related to the study protocol. The patients were advised to avoid other therapies during the exercise period.

Direct healthcare costs included the baseline orthopedic surgeon's visit, the costs of the interventions and additional visits to healthcare providers during the intervention and follow-up period [11].

The statistical analysis was done with Statistical Package for the Social Sciences 15.0 (Norusis/SPSS, Inc., Chicago, IL). The sample size was calculated to detect a mean difference of 10 points in the Kujala score between the treatment groups, using a standard deviation of 13 determined on the basis of our pilot material [12]. To obtain a less than 5% probability of a type-I error and a power of 80%, 27 participants were required in each group. We randomized 56 patients, allocating 28 to each study group.

The primary analysis was intention-to-treat and the primary follow-up time was 9 months from randomization. Comparisons between the groups were performed with analysis of covariance using the baseline scores as a covariate. The secondary follow-up time was 24 months from randomization. In addition, we carried out 'a worst-case scenario' analysis of the data. In this analysis, we assumed that the Kujala score would have been the same as the baseline score (no change), if follow-up data were not available.

The ethical committee of the Hospital District of Helsinki and Uusimaa and the review board of the ORTON Orthopaedic Hospital approved the study protocol.

The arthroscopy findings and surgical procedures in the arthroscopy group are shown in Table 4. The Kujala score improved between randomization and follow-up in the arthroscopy group in those whose arthroscopy findings were normal (N = 5) by 17.0 points and in those with at least one abnormality documented at arthroscopy (N = 22) by 12.0 points (Table 4). The Kujala score improved by 12.8 points among the 17 patients who had at least one abnormality and who had surgical procedures owing to their abnormalities, and by 9 points among those who had abnormalities, but did not have any surgical procedure (N = 5).

Table 5 shows the mean direct healthcare costs and use of healthcare services per patient for PFPS during the intervention and the follow-up period. The mean difference per patient in total direct healthcare costs between the groups was €901 (95% CI 714 – 1095, p < 0.001). The mean number of sick leave days was 8.7 in the arthroscopy group and 1.4 in the control group (p < 0.001).