PURPOSE: To evaluate the short (3 months or less) and longer term effects of exercise therapy on reducing pain intensity and improving function and/or recovery in patients suffering from patellofemoral pain syndrome through a systematic literature review. METHODS We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialized Register (December 2009), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2009-4), MEDLINE, EMBASE, and other databases to December 2009. The primary comparison was between any exercise program mainly aiming at (quadriceps) muscle strengthening versus no intervention/usual care, an exercise program versus other type of intervention or an exercise program versus any other type of exercise intervention. Primary outcomes were pain, knee function and recovery. Data collection and analysis were done by two pairs of two authors who independently selected trials based on pre-defined inclusion criteria, extracted data and assessed the risk of bias. When appropriate data were pooled using the random-effect model. Mean differences (continuous data) and risk ratios (dichotomous data) with 95% confidence intervals were calculated. RESULTS: 23 trials were included in the review involving 1503 participants with age ranging from 14 to 40 years. At short term (-1.52, 95%CI -2.29;-0.76) and long term (-1.30, 95%CI -2.15; -0.46) exercise therapy shows to be effective on pain reduction compared to no intervention. At short term exercise therapy is effective on improving knee function (5.69, 95%CI 0.70; 10.67). At long term these effects are not significant. The effects of exercise therapy are not clearly reflected on the outcome measures for recovery. At short term exercise therapy is more effective on pain reduction than other conservative strategies such as brace, tape or insoles (-9.26; 95%CI -17.47, -1.05). No significant differences in effect were found when comparing exercise strategies for quadriceps muscle strengthening with other exercise strategies such as closed vs. open kinetic chain, hip abductor or abdominal muscle exercise. CONCLUSION: Data from this review show that exercise therapy is effective on reducing pain at short and long term and improving function at short term compared to no treatment/usual care for patients with patellofemoral pain syndrome.