An 18 year old patient presented with right knee pain. MRI exam was performed and the findings are presented.
An 18 years old patient with a recent history of injury at the medial aspect of the knee during athletics was referred to the Radiology Department by his GP. He also complained of occasional locking and limitation of movement. MRI was performed.
On T1 weighted image (fig 1) there was a hypointense lesion of approximately 1 cm in diameter at the lateral aspect of medial femoral condyle. On T2 and T2 fat suppressed weighted images (Fig 2) the lesion had a zonal morphology and was of low signal intensity with a surrounding rim of high signal intensity. PD sequences (fig 3) demonstrated an osteochondritis lesion of approximately 1 cm with fluid signal intensity between the fragment and the donor site. Additionally, subchondral edema was noted at the surrounding bone tissue (fig 4a,b).
In this case, MR imaging demonstrated an osteochondral defect on the lateral aspect of the medial femoral condyle and its partially detachment with fibrous tissue interposition. These features are characteristic of osteochondritis dissecans.
Osteochondritis dissecans (OCD) refers to the acquired fragmentation and possible separation of the articular cartilage and a segment of subchondral bone from the remaining articular surface. Etiology relates to a subchondral fatigue fracture usually as a result of shearing, rotatory or tangentially aligned impaction forces. This may relate to a single traumatic episode or multiple repetitive. Clinically the most common signs are intermittent locking, recurrent effusions, crepitus and persistent pain. The condition usually occurs in younger patients and more commonly in males.
A grading system is used ranging from subchondral contusion with intact articular cartilage (stage 1) to frank separation of an unstable osteochondral fragment (grade 4). The stage-like course of the development of OCD is as follows (fig 5):
Grade 1: Subchondral osseous lesion. The cartilage coverage is macroscopically intact.
Grade 2: Articular cartilage defect without loose body
Grade 3: Partially detached osteochondral fragment.
Grade 4: Loose body formation
In our case the osteochondral fragment was partially detached with fibrous tissue interposition and is classified as osteochondritis dissecans of stage 3.
Plain-film findings are usually negative in the initial stages and the overlying cartilage integrity cannot be assessed. In some patients a subchondral fracture may be seen and in chronic cases there may be subchondral sclerosis. Computed tomography (CT) may or may not demonstrate the subchondral fracture and sclerosis. CT arthrography may demonstrate the chondral defect filled with contrast. MRI is the non-invasive test of choice, as both chondral and subchondral lesions are seen. The associated subchondral fracture or oedema appears hypointense on T1WI and the chondral defect with or without the associated subchondral bone marrow oedema is best demonstrated on FS intermediate WI.
Treatment of osteochondritis dissecans is typically nonoperative for stable lesions and operative for unstable lesions. Unstable lesions can be treated arthroscopically by drilling, which affects bone repair, with subsequent healing. If the central bone fragments are of sufficient size they may be internally fixed with bone pegs or Herbert screws. Outcome depends on a number of factors, including the location and size of the lesion, patient age and treatment. A good clinical outcome is likely when the femoral growth plate is open, when the lesion is small and is stable on MRI. When a cartilage fracture or articular defect is found on MRI, the patient is likely to have a poor outcome.
Osteochondritis dissecans of the knee, stage 3
Based on the provided knee MRI images, the following main features are observed:
In summary, these findings are consistent with signs of a locally unstable osteochondral segment.
Based on the patient’s age, symptomatic presentation (knee pain), and MRI findings showing local osteochondral defects with subchondral bone changes, the following diagnoses or differentials are considered:
Considering the imaging characteristics and clinical information, OCD is the primary concern.
Combining the patient’s gender, age (18 years old, adolescent—common OCD demographic), clinical symptoms (knee pain), and MRI findings, the diagnosis can be confirmed as:
Osteochondritis Dissecans (OCD) of the lateral side of the medial femoral condyle in the right knee, in a partially detached stage (OCD Stage III).
The goals of rehabilitation are to relieve pain, promote osteochondral healing, and restore joint range of motion and function. A gradual, individualized approach following the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, and Volume) is recommended. The following is a brief example:
If the patient experiences significant pain, joint swelling, or worsening functional impairment during rehabilitation, reduce or pause the exercises and seek medical advice promptly.
This report is based solely on the available imaging and medical history, serving as a reference analysis. It does not replace an in-person consultation or professional medical advice. If there are any questions or changes in the patient’s condition, please seek timely evaluation at a qualified medical facility.
Osteochondritis dissecans of the knee, stage 3
