Abstract
An osteochondral lesion in the knee joint is caused by a focal traumatic osteochondral defect, osteochondritis dissecans, an isolated degenerative lesion, or diffuse degenerative disease. An osteochondral lesion with a cleft-like appearance accompanying medial meniscus injury is rare without trauma. We report the case of a 13-year-old boy who complained of right knee pain and swelling, with radiographic findings of an osteochondral defect. Arthroscopic inspection showed an osteochondral lesion in the medial condyle of the femur and tibial plateau accompanying a partial medial meniscus discoid tear. Partial meniscectomy was performed, and a microfracture procedure was carried out on the osteochondral defect. The patient was asymptomatic at 2 years' follow-up. This technique is a relatively easy, completely arthroscopic procedure that spares the bone and cartilage and has yielded a good clinical outcome in a skeletally immature patient who had an osteochondral lesion with a cleft-like appearance.
Articular cartilage is vulnerable to traumatic injury and subsequent degeneration, which appears as a focal traumatic osteochondral defect, an osteochondritis dissecans lesion, or an early isolated degenerative lesion. We present the case of a patient with an osteochondral lesion with a cleft-like appearance accompanying a partial discoid medial meniscus tear. Our surgical technique facilitated anatomic restoration of the osteochondral lesion with a cleft-like appearance in an immature patient.
Case
A 13-year-old boy had complained of right knee pain and swelling 2 years previously. His clinical history was negative for previous trauma. Pain was not accompanied by locking and catching symptoms, but it had gradually increased with participation in sports activities.
A physical examination showed swelling, mild effusion, and medial joint line tenderness in the right knee. The range of motion was between 0° and 140°. Findings of the Watson-Jones and McMurray tests for the medial meniscus were positive. The results of the Lachman test, anterior and posterior drawer tests, and varus and valgus stress tests were normal. The patient had no patellofemoral symptoms.
A plain radiograph showed the presence of a bone defect in the femoral medial condyle (Fig 1). Magnetic resonance imaging (MRI) showed a partial discoid medial meniscus tear, an osteochondral lesion (measuring 10 mm × 28 mm) in the femoral medial condyle, and a chondral lesion in the tibial medial plateau on a T2-weighted gradient-echo image (Fig 2). There was no bone bruise in the femoral medial condyle or the tibial medial plateau.
Fig 1.
An anteroposterior radiograph showed a bone defect in the femoral medial condyle (arrow).
Fig 2.
Preoperative MRI (right knee, T2-weighted gradient-echo image, coronal view) showed a partial discoid medial meniscus tear, an osteochondral lesion (measuring 10 mm × 28 mm) in the femoral medial condyle, and a chondral lesion in the tibial medial plateau.
Surgical Technique
A standard arthroscopic examination was performed through a routine anterolateral portal (Video 1). Arthroscopy showed a tear in the posterior third of the partial discoid medial meniscus, an osteochondral lesion in the femoral medial condyle, and a chondral lesion in the tibial medial plateau (Fig 3). The osteochondral defect of the femoral medial condyle and the chondral defect of the tibial medial plateau were found at the border of the torn partial discoid medial meniscus. The osteochondral lesion appeared cleft-like. The torn partial discoid medial meniscus was reshaped with a punch (Duckling Upbiter; Smith & Nephew, Andover, MA) and a radiofrequency device (ArthroCare, Sunnyvale, CA) inserted through the anterolateral portal. The meniscal rim was left untouched. In addition, a microfracture procedure was performed to correct the osteochondral lesions. Perforations of the subchondral bone at a depth of 3 to 4 mm and with 3- to 4-mm spacing were made with an awl (arthroscopic device awl 30°; Isomedical Systems, Tokyo, Japan) inserted through the anteromedial portal (Table 1).
Fig 3.
Arthroscopic views from anterolateral portal. (A) Tear at middle and posterior thirds of incomplete discoid medial meniscus. (B) Osteochondral defect in femoral medial condyle and chondral defect in tibial medial plateau.
Table 1.
Tips and Pearls of Procedure
| Torn partial discoid medial meniscus: reshape gradually to leave the meniscal rim |
| Microfracture procedure: awl inserted through the anteromedial portal |
| Indication: an immature patient who has an osteochondral lesion with a cleft-like appearance |
Postoperatively, the patient was kept non–weight bearing for 6 weeks, but immediate range of motion was allowed. Activity was limited until 3 months. The knee pain disappeared after surgery, and the patient was able to resume daily and sports activities, but kneeling remained impossible for 2 years after surgery. The Lysholm knee score was 95. A radiograph showed the disappearance of the bone defect and flattening of the femoral medial condyle (Fig 4). MRI showed that the osteochondral lesion had been filled, but the restored medial meniscus displayed increased degenerative changes and abrasion (Fig 5).
Fig 4.
A postoperative anteroposterior radiograph showed disappearance of the bone defect and flattening in the femoral medial condyle (arrow).
Fig 5.
Postoperative MRI (right knee, T2-weighted spin-echo image, coronal view) showed that the osteochondral lesion had been filled, but the restored medial meniscus displayed increased degenerative changes and abrasion.
Discussion
An osteochondral lesion in the knee joint is caused by a focal traumatic osteochondral defect, osteochondritis dissecans, an isolated degenerative lesion, or diffuse degenerative disease.1-3 The conditions that should be differentiated from the condition that affected our patient are a focal traumatic osteochondral defect and osteochondritis dissecans. Osteochondritis dissecans lesions are defined by a structure in which an intact unit of cartilage and subchondral bone detaches from its surrounding matrix. In our patient, there was no loose or free bone. An osteochondral lesion with a cleft-like appearance accompanying medial meniscus injury is rare without trauma. Our patient had never undergone knee surgery. An osteochondral defect in the femoral medial condyle and a chondral defect in the tibial medial plateau were found at the border of the torn partial discoid medial meniscus at the posterior sections. In terms of the mechanism of the osteochondral lesion in this case, it is suspected that the tear of the posterior third of the partial discoid medial meniscus was caused by a defect in the conformity of the tibiofemoral joint. The osteochondral injury to the femoral medial condyle was caused by damaged meniscal margins, and this injury damaged the tibial cartilage.
Discoid medial meniscus, a rare congenital anomaly, was first reported by Cave and Staples,4 and fewer than 70 cases have been reported in the literature.5-7 Various clinical symptoms of discoid meniscus have been reported: Discoid lateral meniscus tends to manifest as hypermobility during childhood without tearing, whereas discoid medial meniscus is asymptomatic in childhood until shown by a tear.8,9 The ultrastructure of discoid menisci differs from that of normal menisci10; this difference in collagen fiber organization and the stress redistribution induced by increased meniscal thickness are factors of vulnerability.11
In terms of treatment, partial meniscectomy was performed. The meniscal rim was left untouched. We avoided total meniscectomy. Postoperative MRI showed that the restored medial meniscus exhibited increased degenerative changes and abrasion. Partial meniscectomy does not restore the function of a normal meniscus. This may be because of the histologic structure of the partial discoid meniscus.10,12 There are several operative methods to treat osteochondral lesions, including the microfracture procedure, mosaicplasty, and autologous cartilage graft. This osteochondral lesion affected a relatively long and narrow area, and the patient was immature. The microfracture procedure was performed. The osteochondral lesion was repaired to some extent. The advantage of this technique is that it is a relatively easy, completely arthroscopic procedure that spares the bone and cartilage. The candidate is an immature patient who has an osteochondral lesion with a cleft-like appearance. The disadvantage is that the repair material is fibrocartilage rather than hyaline cartilage. Partial meniscectomy and the microfracture procedure might not be able to retard the evolution toward medial femorotibial osteoarthritis.13,14 In this case the short-term results were favorable; however, favorable long-term results will require adjustments in the patient's daily and sports activities.15
Footnotes
The authors report that they have no conflicts of interest in the authorship and publication of this article.
Supplementary Data
Right knee arthroscopy. The patient had an osteochondral lesion with a cleft-like appearance accompanying a partial discoid medial meniscus tear. Partial meniscectomy and a microfracture procedure were performed.
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Associated Data
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Supplementary Materials
Right knee arthroscopy. The patient had an osteochondral lesion with a cleft-like appearance accompanying a partial discoid medial meniscus tear. Partial meniscectomy and a microfracture procedure were performed.