Self-reported, unspecific knee pain is highly prevalent among adolescents. A large proportion of the unspecific knee pain can be attributed to Patellofemoral Pain Syndrome (PFPS). There are a number of treatment options for PFPS. Physical therapy has been advocated as one of the cornerstones in rehabilitation of patients with PFPS. Twenty-five years ago, McConnell proposed a multimodal approach that combined several treatment options. The regimen included retraining of the vastus medialis oblique muscle through functional weight bearing activities. This exercise is combined with patellar taping, patellar mobilization, and stretching to improve patellar tracking, reduce pain, and enhance vastus medialis oblique muscle activation. Short term results (<12 months) indicates that multimodal physiotherapy is more effective than placebo treatment.

While treatment for PFPS may be successful for the short-term, long-term results are less promising. A recent review covering the long term prognosis for patients diagnosed with PFPS, reported that only 1/3 of those diagnosed with PFPS and treated conservatively were pain free 12 months after diagnosis. Further ¼ stopped participating in sports because of knee pain.

Predictors of long term outcome (>52weeks) indicate that a long symptom duration, higher age and greater severity at baseline are associated to poorer outcome after treatment. These prognostic factors suggest that an early initiation of treatment might lead to a better long-term prognosis. The purpose of this study is to examine the short and long-term effectiveness of multi-modal physiotherapy compared to standard wait-and-see treatment applied at a very early state of disease among adolescents. The investigators hypothesized a significantly larger proportion of completely recovered patients at three-month follow-up in the interventions group compared to the control group.

Inclusion Criteria:

• Age 15-19 years
• Insidious onset of anterior knee or retropatellar pain of greater than six weeks' duration
• Provoked by at least two of prolonged sitting or kneeling, squatting, running, hopping, or stair walking
• Tenderness on palpation of the patella, or pain with step down or double leg squat
• Worst pain over the previous week of at least 30 mm on a 100 mm visual analogue scale.

Exclusion criteria:

• Concomitant injury or pain from the hip, lumbar spine, or other knee structures
• Previous knee surgery
• Patellofemoral instability
• Knee joint effusion
• Use of physiotherapy for treating knee pain within the previous year
• Use of weekly use anti-inflammatory drugs.