- Research article
- Open Access
- Open Peer Review
Knee arthroscopy and exercise versus exercise only for chronic patellofemoral pain syndrome: a randomized controlled trial
© Kettunen et al; licensee BioMed Central Ltd. 2007
- Received: 27 April 2007
- Accepted: 13 December 2007
- Published: 13 December 2007
Arthroscopy is often used to treat patients with chronic patellofemoral pain syndrome (PFPS). As there is a lack of evidence, we conducted a randomized controlled trial to study the efficacy of arthroscopy in patients with chronic PFPS.
A total of 56 patients with chronic PFPS were randomized into two treatment groups: an arthroscopy group (N = 28), treated with knee arthroscopy and an 8-week home exercise program, and a control group (N = 28), treated with the 8-week home exercise program only. The arthroscopy included finding-specific surgical procedures according to current recommendations. The primary outcome was the Kujala score on patellofemoral pain and function at 9 months following randomization. Secondary outcomes were visual analog scales (VASs) to assess activity-related symptoms. We also estimated the direct healthcare costs.
Both groups showed marked improvement during the follow-up. The mean improvement in the Kujala score was 12.9 (95% confidence interval (CI) 8.2–17.6) in the arthroscopy group and 11.4 (95% CI 6.9–15.8) in the control group. However, there was no difference between the groups in mean improvement in the Kujala score (group difference 1.1 (95% CI -7.4 - 5.2)) or in any of the VAS scores. Total direct healthcare costs in the arthroscopy group were estimated to exceed on average those of the control group by €901 per patient (p < 0.001).
In this controlled trial involving patients with chronic PFPS, the outcome when arthroscopy was used in addition to a home exercise program was no better than when the home exercise program was used alone.
Current Controlled Trials ISRCTN 41800323
- Cartilage Lesion
- Anterior Knee Pain
- Knee Arthroscopy
- Direct Healthcare Cost
- Home Exercise Program
Patellofemoral pain syndrome (PFPS) is a common problem and has an impact on many aspects of daily life [1, 2]. The possibly multifactorial etiology of PFPS is partially unknown and a wide range of conservative and surgical procedures has been used to treat patients with the syndrome .
There is some evidence that exercise therapy reduces anterior knee pain in patients with PFPS . Although many physicians prefer conservative therapy modalities in the treatment of PFPS with unknown origin of pain, in chronic cases and after the failure of conservative treatment, arthroscopy is often carried out. However, although a few randomized controlled trials (RCTs) have compared the effects of various operative techniques [5, 6], no RCTs either analyzing the diagnostic value of arthroscopy or comparing surgical interventions with conservative therapy in the treatment of PFPS have been published. Surgical interventions in PFPS should be based on diagnostic findings suspected to underlie the pain syndrome . Arthroscopy is used to make a specific diagnosis and to perform finding-specific surgical procedures. To further clarify the additional value of diagnostic and operative arthroscopy, we conducted a randomized trial to assess the efficacy of arthroscopy in conjunction with a home exercise program (arthroscopy group) versus home exercise program only (control group) in patients with chronic PFPS.
Inclusion and exclusion criteria among patients with PFPS
The first stage (evaluation in the ORTON Orthopaedic Hospital or in the outpatient clinics of the public hospitals in the Helsinki area)
Age 18 – 40 years
Disabling general illness
Female or male
Reported knee ligamentous or meniscal injuries
Characteristic history of PFPS and symptoms lasting at least 6 months
Previous knee surgery
Patellofemoral pain during knee loading physical activity, such as jumping, running, squatting, or going up or down stairs
Physician diagnosed knee osteoarthritis
Patellofemoral pain when the knee was kept in flexion for a prolonged period, with relief on extension
A history of patellar dislocation; however, subjects with patellar subluxation are included in the study
Other knee problems than PFPS diagnosed clinically (such as jumper's knee)
Other knee problems than PFPS diagnosed radiographically (such as osteochondritis dissecans)
Physical therapy for PFPS within the previous 4 weeks
The second stage (orthopedic surgeon's clinical and radiological evaluation in ORTON)
As in stage one
Clear medio-lateral instability in manual instability measurement
Knee problems other than PFPS
Osteochondritis dissecans, loose bodies in the patellofemoral and tibiofemoral joints
Randomization process and treatment groups
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  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 : 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) , also known as the anterior knee pain score , 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 , patients have described it as easy to understand and as depicting the symptoms well , and the score has been used widely in evaluating patellofemoral disorders in scientific studies. According to Crossley et al  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 .
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 . 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.
Baseline characteristics of the randomized patients
Arthroscopy group (N = 28)
Control group (N = 28)
Female % (N)
BMI, kg m-2
Duration of symptoms, months
One patient in the arthroscopy group and three in the control group were lost to the follow-up (Figure 1). In the arthroscopy group 37% (10/27) and in the control group 20% (5/25) of the patients reported that they had used oral anti-inflammatory analgesics during the follow-up, either during the home training period or afterwards (p = 0.23).
Three patients in the control group insisted on having an arthroscopy after the exercise intervention and prior to the 9-month follow-up. The arthroscopy findings of these patients were normal knee, softening of the patellar cartilage and marginal medial meniscus rupture. These patients participated in the follow-up and were analyzed according to their original group assignment. The absolute changes in the Kujala score in these patients were 7, 13 and -4, while among the remaining patients in the control group the mean improvement was 12.7.
Results of intention-to-treat analysis of outcomes by group
Difference in mean change scores (95% CI)1,2
Kujala score, mean (SD)
1.1 (-7.4 to 5.2)
Pain when descending stairs, VAS mean (SD)
0.9 (-10.1 to 11.9)
Pain when ascending stairs, VAS mean (SD)
2.6 (-10.0 to 15.2)
Pain when standing up from a sitting position, VAS mean (SD)
4.1 (-7.0 to 15.2)
In the arthroscopy group 82% (22/27) and in the control group 76% (19/25) of the patients reported at least moderate improvement at the end of the follow-up period (p = 0.74). When the arthroscopy and control groups were combined, the mean change in the Kujala score among those patients who reported no improvement during the 9-month follow-up was 5.0 (SD 10.5) and among those with at least moderate improvement it was 14.1 (SD 10.8), p = 0.016.
Arthroscopy findings and outcome
Arthroscopy findings and treatment procedures among patients in the arthroscopy group
Number of arthroscopy findings in 28 knees
at baseline, mean (SD)
at 9-month follow-up, mean (SD)
mean change (95% CI)
Articular cartilage lesion; no other findings
14.8 (9.5 to 20.0)1
15.9 (8.7 to 23.0)
Inflamed/scarred plicae; no other findings
6.8 (-11.5 to 25.0)
Meniscal lesion; no other findings
Patellar subluxation; no other findings
Patellofemoral dysplasia; no other findings
Lateral capsular discision
Articular cartilage lesion and inflamed/scarred plicae
Shaving and plica partial resection
Articular cartilage lesion and meniscal lesion
Shaving and meniscal partial resection
17.0 (1.6 to 32.4)
Costs and use of healthcare services
Costs and use of healthcare services among patients with PFPS in the arthroscopy and control groups during the intervention and follow-up period
Number of visits, mean per patient
Direct healthcare costs (€), mean per patient
Type of utilization
Medical specialist care
Physiotherapy (session of 30 minutes maximum)
Total direct healthcare costs (€), mean per patient
Twenty-five (89%) patients from the arthroscopy group and 23 (82%) patients from the control group answered the 24-month follow-up questionnaire. The mean improvement according to the Kujala score was maintained at the 24-month follow-up in both the arthroscopy group and control group (mean scores 12.5 and 9.4, respectively). No difference in the mean change in the Kujala score between randomization and the 24-month follow-up was found (baseline-adjusted difference arthroscopy versus controls was 2.8; 95% CI -4.2 – 9.9, p = 0.42).
Our study shows that arthroscopy did not provide any overall additional advantage for chronic PFPS patients when provided in addition to the training program. Our economic analysis showed that the direct healthcare costs were higher in the arthroscopy group compared with the control group. Moreover, the higher numbers of days on sick leave among the patients in the arthroscopy group indicate that the indirect healthcare costs were also higher in the arthroscopy group.
Our arthroscopy procedure was based on recommendations on the etiology and arthroscopic treatment of PFPS . Despite a statistically insignificant trend towards a baseline difference between the groups in the Kujala score, it is likely that abnormalities in the patellofemoral joint were evenly distributed between our arthroscopy and control groups. Furthermore, when investigating the effects of treatment between the groups, we adjusted our results with the baseline values. Also, in the arthroscopy group, the patients with abnormalities who were operated on using recommended surgical procedures did not show greater improvement than the other patients.
Two patients were shown to have meniscal pathology in arthroscopy. However, both of these patients reported anterior knee pain symptoms at the baseline examination. It is known that some patients with meniscus problems report anterior knee pain symptoms, but we cannot be sure whether these symptoms were in fact due to meniscus pathology in our subjects. These patients were treated according our preliminary pre-determined guidelines, which followed generally accepted recommendations.
We do not know whether the number of abnormalities seen in our arthroscopy group is higher than might be found in a non-symptomatic population. Interestingly, the mean improvement was somewhat better among the patients whose arthroscopic findings were normal. The mechanism responsible for the effectiveness of the treatment among these patients is unknown. Patients with chronic pain expect aggressive treatment and a patient's expectations may influence the clinical outcome independently of the treatment itself . Arthroscopy itself may have a placebo effect . This possible placebo effect does not change the conclusions drawn from our study.
Only patients with symptoms of at least 6 months duration were included in our study and after the follow-up one-fifth of these patients reported no improvement compared with the baseline situation. Although PFPS is usually a non-progrediating condition, our result is in line with earlier findings that, despite adequate treatment, some patients with PFPS have long-term symptoms . Although different stage cartilage lesions seem to be quite common among patients with PFPS, the association between cartilage lesion and symptoms is usually considered to be weak [1, 16]. In our previous study on PFPS patients, only severe, possibly pre-arthrotic, cartilage injury predicted persistent long-term symptoms . In the present study only one patient had a stage IV cartilage lesion and his Kujala score improved by 8 points.
While our primary aim was to investigate the possible additional benefit of knee arthroscopy among patients with PFPS, an exercise program consisting of simple lower-limb stretching and strengthening exercises was used as a generally accepted treatment to improve the adherence to our arthroscopy versus no-arthroscopy study design. As our patients had experienced prolonged knee symptoms, it would have been difficult and perhaps unethical to use a no-treatment control group. Also, the number of withdrawals and dropouts would have been higher among patients without any treatment. Although three patients from the control group insisted on an arthroscopy during the follow-up, their outcome was no better than that reported by the other controls.
The fairly high mean weekly exercise frequency indicated good treatment compliance in both groups. A speculative, alternative interpretation of our results is that exercise was effective both with and without the addition of arthroscopy. It should be emphasized that the primary aim was not to investigate the effectiveness of exercise therapy in patients with PFPS. In fact, we found no association between frequency of weekly exercise and improvement (data not shown). Despite that, our results are in line with the earlier view that exercise therapy may be an effective treatment for PFPS .
Competitive athletes, who may have had pain syndrome related to extreme loading and perhaps not be willing to follow the present treatment protocols, were excluded from the study. Also, patients younger than 18 and those over 40 years of age were excluded. Our results are valid for young adults who do not participate in competitive sports. Our study shows that an unselected group of chronic PFPS patients received no benefit from arthroscopy in addition to exercise therapy. The study does not show whether there are any subgroups of PFPS patients who would benefit from arthroscopy. However, this is possible.
Although our primary end-point was at 9 months, as we wished to avoid many of the random factors, which can influence longer follow-ups, we also collected data at 24 months. Extending the follow-up did not change the result.
In conclusion, on the basis of our randomized study, which was planned using available knowledge on the diagnosis and methods of treating PFPS, arthroscopy cannot be recommended for patients with chronic PFPS.
We wish to thank the physicians, physical therapists and nurses at the ORTON Orthopaedic Hospital and at the hospitals of the Hospital District of Helsinki and Uusimaa for their contributions to the study. This research was supported by a grant from The Social Insurance Institution of Finland.
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