The goal of this clinical trial is to compare in distalising tibial tubercle osteotomy procedure group fast rehabilitation to traditional rehabilitation.

The main questions it aims to answer are:

• Will the novel accelerated rehabilitation protocol lead to faster recovery and improved functional outcome at 6, 12 and 24 weeks compared with the conservative rehabilitation protocol?
• Will the complication rate be similar in both groups?

Participants will be following fast rehabilitation or the traditional rehabilitation guidelines after distalising tibial tubercle osteotomy procedure according to the randomisation.

Researchers will compare fast rehabilitation group to the traditional rehabilitation group to see if recovery and functional outcome is improved in fast rehabilitation group and complication rate will be similar in both groups.

Patella alta is a clinical condition where the patella is positioned too proximal in relation to the femoral trochlea. Such an abnormality may cause patellar instability and predispose to recurrent patellofemoral dislocations and patellofemoral pain. There are no conclusive guidelines for determining a threshold for too high positioned patella, as several different methods have been described to measure patellar height. As a surgical solution, distalising tibial tubercle osteotomy has been described to correct excessive patellar height.

In the early phase of the distalising tibial tubercle osteotomy postoperative protocol, weightbearing and knee flexion are limited with a brace commonly for 4-8 weeks. The potential risks for adverse effects associated with the limitation rehabilitation protocol include a delay in regaining knee range of motion, stiffness and muscle weakness. As a result, recovery from surgery is delayed and may lead to additional procedures and long-term morbidity in knee function.

This is a prospective, randomised, controlled, single-blinded, single centre trial comparing a novel accelerated rehabilitation protocol with the traditional, motion restricting rehabilitation protocol. All skeletally mature patients aged 35 years and younger, referred to as the distalising tibial tubercle osteotomy procedure group, are eligible for inclusion in the study. Patients will be randomised to either the fast rehabilitation group or the traditional rehabilitation group. Patients with patellar instability will be additionally treated with medial patellofemoral ligament reconstruction.

The hypothesis of the trial is that the novel accelerated rehabilitation protocol will lead to faster recovery and improved functional outcome at 6, 12 and 24 weeks compared with the conservative rehabilitation protocol. A secondary hypothesis is that the complication rate will be similar in both groups.

The study will document short-term recovery and the planned follow-up will be 3 years. After the 1-year follow-up, the trial results will be disseminated in a major peer-reviewed orthopaedic publication.

Inclusion Criteria:

• Symptomatic patella alta with recurrent dislocation or subluxation. Long-lasting anterior knee pain not responding to rehabilitation.

Exclusion Criteria:

Radiographic:

• Open growth plates
• Iwano [8] grade III and IV changes in patellofemoral joint
• Caton-Deschamps <1.1 in MRI
• PTI >50% in MRI
• High grade trochlear dysplasia

General:

• Refuses to participate in the study
• Aged less than 15 or more than 35 years
• Severe neurological, pulmonal or cardiovascular comorbidities that are contraindications for surgery
• Lack of adequate co-operation
• Does not adequately understand written and spoken instructions in the local language

Those patients who decline to take part in the trial will be asked to join a follow-up cohort as a background population. The patients in this follow-up cohort will be treated "as normal" without allocation, but the follow-up questionnaires will be the same as those given to the randomly assigned population. The patients in the follow-up cohort will also be asked to provide informed written consent.

The copyright of the trial research data will be owned and created by the participating research parties. The data will be shared among all participating researchers who will receive access to the data after the trial is completed. Due to confidentiality and legal agreements, public data sharing will be restricted because we only have permission to hold the data in the specific research server, not to transfer data. Under certain circumstances, for example, when a new member joins the collaboration, we will grant access to the data.