Interventions
The local exercise therapy group will focus on strengthening knee and hip muscles three times a week for 6 weeks. Once a week, patients will train with the support of a physiotherapist. The physiotherapist gradually increases the intensity of the exercises improving muscle endurance. The exercises will be supplemented with mobilisations of the patellofemoral joint. Twice a week, patients train at home following a prescribed exercise program writing down their work-out in an exercise journal.
The spinal manual therapy group will be treated one a week for 6 weeks. Before the first intervention an experienced manual therapist performed a clinical examination of the lower back, SIJ, hip and knee. Anatomical maps showing innervation areas of spinal nerve roots will be used to explain the regional interdependence model in the treatment of anterior knee pain. Manual therapy treatment will include manipulations of the thoracolumbar (T12-L3) region or SIJ as well as hip joint. Manipulation will be conducted if a restriction of range of motion will be found in any of the regions. Patients will also be asked to do home exercises focusing on mobilizing the thoracolumbar region and to write down their performance in an exercise journal.
The allocation of the patients to their treatment group will be concealed from the researcher that assesses the outcome measures.
Outcome measures The following baseline characteristics will be self-reported: age (in years), weight (in kg), height (in cm), duration of symptoms (in months), weekly participation in sport (yes/no), previously receiving exercise therapy treatment for the knee (yes/no). Patellofemoral chondral lesions will be graded using the Kellgren and Lawrence system for classification of osteoarthritis (grade 0 = definite absence of X-ray changes of osteoarthritis, grade 1 = doubtful joint space narrowing and possible osteophytic lipping, grade 2 = definite osteophytes and possible joint space narrowing).
Knee pain, functionality and force will be measured using validated measurement instruments. Pain and functionality will be our primary outcomes. Maximum, minimum and current pain intensity will be indicated on a 0-100 mm VAS line. Functionality will be measured using the Dutch version of the anterior knee pain scale (AKPS). The AKPS questionnaire consists of 13 items assessing subjective symptoms and functional limitations totalling a maximum score of 100. Our secondary outcome, maximum voluntary peak force (MVPF) of the quadriceps, will be measured using a Biodex system 3 isokinetic dynamometer (Biodex Medical Systems, Inc., Shirley, NY, USA). This system has shown sufficient reliability and validity for position, torque and velocity measurements in clinical and research settings. Patients will be assessed before intervention (=baseline), at 6 weeks (=immediately after the last intervention) and at 12 weeks (=6 weeks after the last intervention).
