A 15-year-old rugby player who sustained a right knee direct injury. Since the injury he had intermittent right knee swelling associated with any form of strenuous activity. Clinical examination revealed an effusion in the right knee. The left knee was far less symptomatic, with only occasional pain and crepitus.
Radiographs of the right knee (Fig. 1) demonstrated a large joint effusion and normal osseous structures. An MR study (Fig. 2 – right knee; Fig. 3 – left knee) revealed bilateral focal osteochondral defects in the medial patellar facets.
Osteochondral lesions / defects (OCD) are a common pathology of subchondral bone and overlying cartilage in children and adolescents. The most common joint to suffer from an OCD is the knee joint, involving the medial femoral condyle, with the patella being a rare location. The presence of bilateral and symmetrical patellar osteochondral defects is even rarer and in the English literature, only a few cases have been described [1, 2].
The aetiology of OCDs is not fully elucidated. According to common hypotheses, repetitive microtrauma, local ischaemia, disturbance of normal ossification of accessory centres during maturation and hereditary factors are considered contributory to pathophysiology of OCD.
It is a well-known fact that OCD predisposes a patient to an early degenerative change in the joint.
From imaging perspective radiography is the first modality is used to diagnose OCD and monitor healing process. However, MRI is the most accurate and sensitive tool which enables to diagnose OCD at early stages, grade OCD process and determine a lesions’ healing potential. A fluid-like signal at the interface of the OCD and the native bone is indicative of instability. However, at times it is difficult to confidently conclude whether an osteochondral defect is stable or not and in these cases arthroscopy has a major role not only in confirming the stability of an of OCD, but in treating the lesion.
Treatment of OCD varies widely depending on the age of patient and the stage of OCD from activity adjustment and reduced weight bearing (stable, less severe disease) to operative management (unstable defect). Surgical treatment is reserved for patients who do not improve with conservative treatment or with a suspected unstable lesion. Operative procedures include debridement, microfracture, osteochondral autografting and autologous chondrocyte implantation.
A better prognosis is associated with early age; for instance in juvenile group healing potential is up to 75% [3] whereas in the adolescent group is about 50% and in the adult group chances of healing are low even with advanced treatment. The important factors influencing prognosis include size and location of the lesion, duration of the symptoms, fragment stability and appearances of the overlying cartilage.
Take Home Messages:
• MRI is the most useful and sensitive technique in evaluating and staging OCD.
• Presence of fluid-like signal at the interface of OCD and native bone is indicative of instability.
• Bilateral patellar OCD is probably underestimated as often contralateral knee is asymptomatic.
Written informed patient consent for publication has been obtained.
Bilateral patellar osteochondral defects
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on the provided X-ray and MRI images, there is a notable local osteochondral defect behind the right patella, showing irregular subchondral bone and abnormal local signal. In some sequences, there are osteochondral fragments with irregular edges. On T2-weighted images, there is high signal change indicating joint effusion or “fluid-like signal” possibly distributed along the defect edge, suggesting a certain degree of instability.
In addition, when comparing to the left knee images, similar abnormal signals can be observed behind the patella, although smaller in range, indicating that both patellae have comparable osteochondral lesions but milder on the left side.
A small amount of joint effusion is present, consistent with clinical findings of joint swelling and effusion. No obvious tear or significant edema is observed in the local soft tissues, with the primary lesion focused at the osteochondral interface.
1. Patellar Osteochondritis Dissecans (OCD):
· Common in adolescents and athletes, commonly affecting the medial femoral condyle or the posterior surface of the patella;
· Repeated stress or trauma can lead to subchondral bone ischemia and necrosis, resulting in osteochondral detachment or loosening;
· Imaging may show subchondral bone disruption, irregular signals, and signs of fluid infiltration around the lesion.
2. Osteochondral Fracture:
· May occur after intense impact or acute injury, involving a local fracture of the patella or femur;
· Often accompanied by marked acute pain and a visible fracture line, usually presenting with severe clinical symptoms;
· MRI findings could include bone marrow edema and a fracture line; however, this case exhibits more chronic changes, making fracture less likely.
3. Cartilage Lesions (e.g., subchondral cyst or articular cartilage damage):
· Articular cartilage wear or localized cartilage defects can present with similar imaging findings;
· In adolescents, isolated cartilage lesions are often associated with trauma or weight-bearing activities;
· However, the T2 high signal at the periphery and the subchondral changes in this case are more suggestive of osteochondritis dissecans.
Considering the patient is a 15-year-old adolescent with a history of sports (rugby) and recurrent knee swelling, along with MRI findings of significant osteochondral defects and subchondral high signal changes behind both patellae, and fluid-like signals suggesting potential instability, the most likely diagnosis is bilateral patellar osteochondritis dissecans (OCD).
If doubt remains clinically or to assess the stability of the lesion and the extent of cartilage damage more accurately, arthroscopic evaluation and intervention could be considered.
1. Conservative Treatment:
· Primarily indicated for stable or mild lesions, achieved by minimizing high-impact stress on the knee (limiting running, jumping, deep squats), wearing knee braces, or using crutches to reduce load;
· Use anti-inflammatory and analgesic medications (e.g., NSAIDs) to relieve pain and swelling, and schedule regular imaging follow-ups to monitor healing.
2. Surgical Intervention:
· If the lesion appears unstable (MRI suggesting fluid infiltration along the osteochondral interface) or if conservative treatment fails, arthroscopic debridement, fixation, or graft repair may be considered;
· Large osteochondral defects may be treated with autologous osteochondral transplantation (Mosaicplasty) or autologous chondrocyte implantation (ACI).
3. Rehabilitation and Exercise Prescription:
(1) Acute Phase and Early Postoperative Phase:
· Focus on joint immobilization and protection, with passive or assisted active range-of-motion exercises to avoid excessive load;
· Engage in upper limb and core strength training to maintain overall fitness.
(2) Subacute Phase:
· Once there is no significant pain or swelling, begin non-weight-bearing or low-weight-bearing exercises (e.g., wall sits, small-range squats, balance training);
· Train 2-3 times per week, each session lasting 10-20 minutes, starting with low intensity and gradually increasing duration and depth.
(3) Strength and Functional Recovery Phase:
· Gradually increase resistance training, such as light-weight leg extensions, cycling, or swimming with low impact aerobic activity;
· Recommended 3-4 times per week, each session 20-30 minutes at moderate intensity, while regularly monitoring joint response.
(4) Advanced Training and Sport-Specific Drills:
· Following improvements in knee stability and muscle strength, gradually introduce running and rapid change-of-direction exercises, returning to contact sports only after evaluation by a physician or rehabilitation specialist;
· Emphasize progressing from jogging to sprinting, combined with flexibility training (stretching, joint mobility) and neuromuscular coordination exercises.
Adhere to the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, Volume), adjusting based on symptom control and functional status. If pain or swelling worsens, seek medical advice or modify the training plan.
Disclaimer: This report is based on the provided clinical history and imaging data and is for reference purposes only. It does not replace an in-person consultation or professional medical advice. Specific treatment decisions should be made by specialists or a medical team based on the individual clinical scenario.
Bilateral patellar osteochondral defects
