A Comparison of Two Different Treatment Approaches for Adolescents With Osgood Schlatter

The scale contains 7 questions answered through a 0-4 likert scale. The scale is normalized to a 0-100 score with 100 be, with zero representing extreme knee problems and 100 representing no knee problems.

The question pertaining to Patient Acceptable Symptom State (PASS) are designed in collaboration with patient representatives. The recall period will be one week, and the outlook period a 'few months' as in previous applications in musculoskeletal conditions with fluctuating symptoms:

"If you consider your knee pain during the past week, and how it affects your ability to do activities of daily living (for example participating in school, in sports, and socially), would you consider your current symptom state acceptable for the next few months?". The proportions of yes/no in each group will be captured

The scale contains 6 questions answered through a 0-4 likert scale. The scale is normalized to a 0-100 score with 100 be, with zero representing extreme knee problems and 100 representing no knee problems.

Weekly average of pain flares over a 4-week period leading up to the 5 months visit. Pain flares are defined as episodes of of 4 or more on the 0-10 numerical pain rating scale with 0 being no pain and 10 being worst pain imaginable.

Pain intensity as defined as the highest rating of pain on the 0-10 numerical pain rating scale with 0 being no pain and 10 being worst pain imaginable.

The level of participation in sports will be captured through weekly monitoring. Participants will be asked if they have been participating in sports in the preceding week, and for how many hours. A 4-week average leading up to the 5 month visit will be calculated

Minutes of Moderate to Vigorous Physical Activity (MVPA) will be captured using waterproof 3 axis 12 Hz accelerometers (SENS®, Copenhagen, Denmark) applied once to the participants thigh during the enrollment visit using an adhesive patch. A 4-week average leading up to the 5 month visit will be calculated

According to WHO recommendations a daily minimum of 60 min of MVPA is needed to stay healthy for 5-17 year olds.Thus being at either under or above this cutoff during a 4-week average leading up to the 5 month visit will be assessed, in addition to a continuous comparison between the two groups of minutes of MVPA during the same time period.

Participants will also be asked during clinical visits if they are satisfied with the current extent of their sports participation (Yes/No questions).

Involvement of the tendon is common in patients with Osgood Schlatter. Signs of tendinosis will be assess through ultrasound scanning by evaluating either the tendon as thickened or with hyperemia through color-doppler mode.

In Osgood-Schlatter patients, associated signs of bursitis have shown to be prognostic of a worse outcome. Signs of tendinosis will be assess through ultrasound scanning by evaluating either the infrapatellar bursa as thickened or with hyperemia through color-doppler mode.

In Osgood-Schlatter patients, gradings of severity have shown to be prognostic of a worse outcome. Severity will be graded according to the ad modum Flaviis 1-4 grading, or as 'normal'.

Adolescents will rate their pain from performing the Anterior Knee Pain Provocation test on the 0-10 numerical pain rating scale with 0 being no pain and 10 being worst pain imaginable.

Adolescents will rate pain experienced during a maximal isometric knee extension strength test on the 0-10 numerical pain rating scale with 0 being no pain and 10 being worst pain imaginable.

To evaluate local hyperalgesia specifically at the tibial tubercle, handheld algometry will be used to detect the pressure (kPa) needed to evoke pain (going from no pain to the slightest sensation of pain) on the tibial tubercle on both knees

To evaluate the capacity of the quadriceps femoris muscle inserting at the site of pain, handheld dynamometry will be used to measure maximal isometric force generation which will be normalized to bodyweight and lever-length (Nm/kg).

As a measure of sports-specific skill, a countermovement jump will be performed to record jump height (cm), using high-speed video analysis via a smartphone app (My Jump 2).

To assess patient-assessed improvement or worsening, study personnel will ask participants to rate their perceived level of change from their first visit on a 7-point likert scale ranging from 'Much worse' to 'Much better'.

Study personnel will ask participants to rate their problems with an important activity using the Patient-Specific Functional Scale. They are asked to name a single important activity of their own choosing. Participants then rate their functional limitation with activity on a 0 to 10 scale, where 0 corresponds to being unable to perform activity and 10 is being able to perform activity at same level as before knee pain.

To capture level of kinesiophobia, that is, the fear of pain due to movement or exercise, a type of fear-avoidance behavior, the patient-reported 17-item Tampa Scala of Kinesiophobia (TSK-17) will be used.

Self-rated health will be collected through the 0-100 VAS for general health.

The scale contains 8 questions answered through a 0-4 likert scale. The scale is normalized to a 0-100 score with 100 be, with zero representing extreme knee problems and 100 representing no knee problems.

Using the EQ-D5-Y scale, participants are asked on a 3-point likert scale ranging from 1 (I have no pain or discomfort), to 3 (I have extreme pain or discomfort).

Participants are asked if they perform either 1) at a higher level than before onset of knee pain, 2) at the same level as before onset of knee pain, or 3) at a lower level than before onset of knee pain

Participants are asked if they are either 1) more physically active than before onset of knee pain, 2) just as physically active as before onset of knee pain, or 3) are less physically active as before onset of knee pain

For the subgroup of participants not being active in sports at baseline, the week in which they return to sports participation will be recorded and compared between groups.

Hyperemia of the tibial tubercle will be assess through ultrasound scanning by evaluating hyperemia ad modum Öhberg 1-4 through color-doppler mode.

Known pain when palpating the tibial tubecle during clinical examination change from baseline

Adolescents will rate pain experienced during the CMJ test on the NPRS 0-10.

As a measure of power, a countermovement jump will be performed to record jump and power-production (watts), using high-speed video analysis via a smartphone app (My Jump 2).

Between-group change in knee flexion angle, assessed by smartphone-inclinometry during a modified Thomas Test will be compared.

Participants are asked if they believe the treatment recieved have been succesful or not (Yes/No question)

Using the EQ-D5-Y scale, participants are asked on a 3-point likert scale ranging from 1 (I have no problems performing my usual activities), to 3 (I am unable to perform my usual activities).

The scale contains 7 questions answered through a 0-4 likert scale. The scale is normalized to a 0-100 score with 100 be, with zero representing extreme knee problems and 100 representing no knee problems.

Potential harms and adverse events will be assesed through open-ended questioning during clinical visits in order to assess if further examination or treatment is warranted, and to classify events according to the severity on from Grade 1-5 Using the Common Terminology Criteria for Adverse Events (CTCAE) grading:

• Mild: Asymptomatic or minor symptoms; clinical or diagnostic observations only; no intervention needed
• Moderate: Minimal, local, or non-invasive intervention indicated
• Severe: Medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling
• Life-threatening consequences (i.e., immediate risk of death); urgent intervention indicated
• Death related to adverse event