An osteochondral fragment detached from the knee joint surface first causes pain associated with strain and later locking symptoms
The change can usually be seen on plain x-ray, best in so-called tunnel view. MRI provides valuable additional information on the stability of the osteochondral fragment.
In children who are still growing, it is possible to achieve ossification of most developing osteochondritis foci by conservative reduction of stress on the joint for 3-6 months. After the years of growth, symptomatic unstable or detached osteochondral fragments are fixed surgically.
The disease is most commonly diagnosed at growing age but rarely in children below the age of 10 years.
Definition and aetiology
Osteochondritis is a condition of subchondral bone where an osteochondral fragment slowly detaches from the weight-bearing joint surface.
The aetiology of the condition is unknown. Suggested causes include inflammation, ischaemia, repetitive microtrauma and defective ossification.
Symptoms and signs
Gradually increasing pain associated with strain
A feeling of the knee giving way, swelling
At later stages, as a consequence of the detached fragment, locking tendency develops.
With the patient's leg hanging down and the knee bent, internally rotate the leg. When you ask the patient to extend the knee, there will be pain at the medial condyle at 30° flexion. Rotating the leg externally will eliminate the pain (Wilson's test).
A detached fragment is usually readily visible on X-ray (Images 12) but the tunnel view is the most sensitive projection. As the condition is often bilateral, both knees must be radiographed.
MRI is often done as part of the diagnostic procedure. It will reveal a focus of osteochondritis at an early stage of the disease, already, and facilitate assessment of the stability of the focus, the quality of the surrounding bone and the condition of the cartilage surface.
In the knee, a focus of osteochondritis most often (> 75%) occurs in the outer edge of the medial femoral condyle.
Treatment
Treatment depends on the patient's bone age and the characteristics of the detached osteochondral fragment.
MRI is usually needed to choose the line of treatment in growing children with OCD, and these patients should be treated in specialized care.
In growing children, spontaneous ossification is probable; pausing hobbies causing stress on the joint, and follow-up are often sufficient for treatment. Sometimes weight-bearing may be restricted and the patient instructed to use crutches and an orthosis to support the knee. The duration of conservative treatment varies between 3 and 6 months.
Spontaneous healing is not very likely after epiphyseal closure, and symptomatic osteochondritis should be treated surgically.
In the operation, the detached focus and its base are revitalized, followed by fixation with resorbable pins or metal screws. Bone grafting is often also required to ensure ossification. The aim is to restore the congruence of the joint surface in order to avoid premature osteoarthritis.
After surgery, crutches should be used for 4-6 weeks and hobbies can be resumed in about 3-4 months.
References
Andriolo L, Candrian C, Papio T et al. Osteochondritis Dissecans of the Knee - Conservative Treatment Strategies: A Systematic Review. Cartilage 2019;10(3):267-277. [PubMed]
Andriolo L, Crawford DC, Reale D et al. Osteochondritis Dissecans of the Knee: Etiology and Pathogenetic Mechanisms. A Systematic Review. Cartilage 2020;11(3):273-290. [PubMed]
Chau MM, Klimstra MA, Wise KL et al. Osteochondritis Dissecans: Current Understanding of Epidemiology, Etiology, Management, and Outcomes. J Bone Joint Surg Am 2021;103(12):1132-1151. [PubMed]
Heyworth BE, Kocher MS. Osteochondritis Dissecans of the Knee. JBJS Rev 2015;3(7). [PubMed]