Aim of the research project:

The entire research project aims to investigate human peripheral joints (knee, foot & ankle, elbow, wrist & hand) by dynamic 4D radiographic imaging acquisition during real-time motion.

Aim of the specific study on Patellofemoral pain syndrome (PFPS) patients:

This study aims to investigate kinematics and motion changes pre and post physiotherapy intervention in patients with patellofemoral pain syndrome (PFPS) and compare them with a healthy control group.

Aim of the specific study on patients undergoing ACL reconstruction:

This study aims to investigate kinematics and motion changes pre and post-surgical intervention in patients with ACL injury that require surgical reconstruction and compare them with a healthy control group.

Study on PFPS patients:

Non-randomized Control Clinical Trial. The patient that satisfies inclusion and exclusion criteria is informed about the nature study at the orthopaedic outpatient clinic. If necessary, the study coordinator provides additional information to the patient. Informed consent will be obtained prior to inclusion in the study. The patient will be asked to undergo a dynamic scan of the knees prior to and after the physiotherapy treatment. The physiotherapy treatment is not specifically controlled but best evidence-based guidelines are provided to the patient's physiotherapist in order to have an intervention as homogeneous as possible. Guidelines suggest a tailored and progressive exercise program to improve muscle strength and control, joint mobility, and patient understanding of the problem and how to manage it. Additional interventions like tape or manual treatment can also be implemented but should not be exclusive. During imaging acquisition, the patients lay on the CT's bed with the lower limb inside the gantry. They are asked to perform a repetitive movement of the knee into different planes of motion (i.e. flexion-extension). Before the start of the dynamic CT scan protocol, a physical examination is performed by a physiotherapist. It consists of muscle strength (dynamometer) and joint ROM assessment. VAS scale and Kujala and KOOS questionnaires will be also administrated to the patients. Healthy volunteers will be provided with a brief explanation of the study the moment they make contact to be involved. Further information and informed consent will be obtained on the day of the scan. Identical procedure for the CT scan and physical assessment used with the patient will be used for the healthy subjects.

Study on patients with ACL injury:

Non-randomized Control Clinical Trial. The patient that satisfies inclusion and exclusion criteria is informed about the nature study at the orthopaedic outpatient clinic. If necessary, the study coordinator provides additional information to the patient. Informed consent will be obtained prior to inclusion in the study. The patient will be asked to undergo a dynamic scan of the knees prior to and approximately 6 weeks after ACL surgical reconstruction. Type of surgical intervention is on surgeon discretion following Best-Evidence practice guidelines.

During imaging acquisition, the patients lay on the CT's bed with the lower limb inside the gantry. They are asked to perform a repetitive movement of the knee into different planes of motion (i.e. flexion-extension). Before the start of the dynamic CT scan protocol, a physical examination is performed by a physiotherapist. It consists of muscle strength (dynamometer) and joint ROM assessment. VAS scale and Lysholm and IKDC questionnaires will be also administrated to the patients. Healthy volunteers will be provided with a brief explanation of the study the moment they make contact to be involved. Further information and informed consent will be obtained on the day of the scan. Identical procedure for the CT scan and physical assessment used with the patient will be used for the healthy subjects.

Study patient with PFPS:

Inclusion Criteria:

patellar/anterior knee pain, provoked by functional activities such as Squatting, Ascending/Descending stairs, Prolonged sitting, Kneeling, Jumping and/or running.

Exclusion Criteria:

• Metallic implants in the proximity of the knee.
• Affections of the Central Nervous System, including Cerebellar dysfunction, Stroke, ALS and MS, affect the strength, motor control and/or coordination of human joints and produce "abnormal" movement patterns;
• Affections of the Peripheral Nervous System of the lower limb, including Lumbar radiculopathy, Peripheral nerve entrapment and Neuropathy, affect the proprioception and muscle force.
• Pregnant women.
• Inflammatory Conditions
• Hyperlaxity
• Patella Dislocation
• knee injection less than 3 months

Study patient with ACL injury:

Inclusion Criteria:

ACL that requires surgical reconstruction. Imaging findings of ACL injury (MRI)

Exclusion Criteria:

• Metallic implants in the proximity of the knee.
• Affections of the Central Nervous System, including Cerebellar dysfunction, Stroke, ALS and MS, affect the strength, motor control and/or coordination of human joints and produce "abnormal" movement patterns;
• Affections of the Peripheral Nervous System of the lower limb, including Lumbar radiculopathy, Peripheral nerve entrapment and Neuropathy, affect the proprioception and muscle force.
• Pregnant women.
• Inflammatory Conditions