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A patient, aged 16 years, presented to the office with approximately 6 years of episodic left knee pain. The pain started during football season but he couldn’t recall any injury. The pain was sharp in nature and the patient had difficulty ambulating after games.
The pain improved in the off season but continued to bother him on occasion over the years. The pain has progressed over the past several months and the patient reported it hurt with activities such as climbing stairs, jumping, and running. He had occasional swelling but denied any locking or giving way of the knee.
His primary care provider prescribed physical therapy, but it did not help.
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The patient’s left knee x-ray and magnetic resonance imaging (MRI) reveal osteochondritis dissecans with an in situ lesion of the medial femoral condyle.
Osteochondritis dissecans (OCD) is a defect in the articular cartilage and subchondral bone that can present in varying degrees of severity. Injury can range from softening of the articular cartilage to detachment of an osteocondral lesion creating a displaced fragment or loose body.
Typical presentation includes athletic males aged less than 18 years with unilateral involvement. Lesions are most often located in the posterior lateral medial femoral condyle. Pain is usually activity related and poorly localized.
Although there is no single known cause of OCD, the most widely accepted etiology is repetitive trauma. The pathology starts with softening of the articular cartilage, progressing to cartilage separation, then partial detachment of the lesion, and finally osteochondral detachment.
Most OCD lesions can be seen on x-ray but an MRI is routinely ordered to determine size of the lesion and if the fragment is detached. The Clanton and Delee classification system is used to describe OCD lesions and is divided into four progressive stages:
- Stage one is a depression of the osteochondral fracture
- Stage two is a fragment attached to an osteochondral bridge
- Stage three is a detached non-displaced fragment
- Stage four is a displaced fragment
Lesions assessed arthroscopically can be classified using the International Cartilage Repair Society (ICRS) scale of OCD lesions:
- Type 1 is a stable lesion with softened but intact articular cartilage
- Type 2 has partial articular cartilage discontinuity but stable when probed
- Type 3 has complete articular cartilage discontinuity but no detachment
- Type 4 is an empty defect with complete detachment or loose body.
Juvenile OCD, occurring in patients with open growth plates, has a better prognosis in terms of healing with non-operative treatment compared with lesions in adults. Stable lesions in children with open physes can be treated nonoperatively with a period of non-weight bearing and bracing.
The spectrum of non-operative treatment varies widely from non-weight bearing in a cylinder cast for 3 months to 6 weeks of walking with a crutch and immediate gentle range of motion. Healing rates approach 50% to 75% with conservative treatment.
Surgery is indicated if non-operative treatment fails in patients with stable lesions. Arthroscopy and transarticular drilling are commonly performed to create vascular channels to the affected bone and cartilage to promote healing. Fibrocartilaginous tissue is formed at the drill hole sites. Post-operative rehabilitation may include a period of 4 weeks non-weight bearing and a slow, progressive return to activity thereafter.
Unstable OCD lesions measuring greater than two cm require stabilization with some form of fixation. Arthroscopic techniques for internal fixation include compression screws, Kirscner-wire (K-wire) fixation, bone pegs, and bioabsorbable pins, and nails. The goal of fixation is to stabilize the lesion, promote healing, and halt the progression of arthritis. Lesions found to be loose during arthroscopy may be peeled back so that debridement can be performed prior to reduction and pinning.
Unstable osteochondral lesions that are completely detached from underlying bone and irreducible should be treated with osteochondral autologous transplantation (OAT). Microfracture (MF) is generally used for smaller detached chondral fragments.
OAT procedure has shown improved long term rates of return to sports over microfracture in patients with ICRS type 3 and 4 OCD lesions. Both OAT and MF have similar results at one year post operatively.
However, due to several proposed factors including poor cartilage repair and decrease strength of fibrocartilage reparative tissue with MF, long term results are less favorable with this technique.
Dagan Cloutier, MPAS, PA-C, practices in a multispeciality orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants (JOPA).
References
- Schroeder GD, Lynch ST, Patel RM, Williams JR, Weathorford BM, Sarwark JF. Orthopedic Knowledge Online Journal. 2013; 11(3).
- Karadsheh M. Osteochondritis dissecans. Ortho Bullets. Retrieved from: http://www.orthobullets.com/sports/3028/osteochondritis-dissecans.
All electronic resources were last accessed on June 5, 2015.
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