Osteochondral Fracture in First Episode of Patellar Dislocation: Case Report and Literature Review

Abstract

Objectives

To present a case of osteochondral fracture in a first episode of patellar dislocation.

Materials and Methods

Female patient, 15 years old, with no prior medical history, who experienced a valgus mechanism of the left knee, resulting in pain and functional impairment. Physical examination revealed swelling of the left knee and anterior pain, with painful weight-bearing and limited flexion to 50-60°. Radiographs of the knee showed an intra-articular fragment. Further assessment with computed axial tomography (CT) of the knee revealed an osteochondral fracture of the left patella with a free intra-articular body. The patient was managed surgically via medial arthrotomy, which allowed visualization of the free intra-articular body and an osteochondral fracture of the medial facet of the patella. Osteosynthesis was performed using three mini cortical screws (1.3 mm, Compact Hand, Synthes®) in a triangular configuration, achieving anatomic reduction.

Results

The patient experienced an uneventful postoperative course, maintaining weight-bearing status until physiotherapy began at 6 weeks, initiating with partial support and progressing gradually. At 6 months, she was asymptomatic and had progressively regained her physical activities.

Conclusion

Osteochondral fractures in the context of a first patellar dislocation require prompt recognition and management, as they involve the integrity of the articular surface and have a high potential for degenerative changes.

Keywords

osteochondral fractures - patellar dislocation - articular cartilage injuries

Introduction

Osteochondral fractures in the setting of acute patellar dislocation have an incidence of between 39% and 71%. They occur more frequently in the younger population. These injuries can be overlooked, which can cause pain and long-term complications.[1] [2]

Clinical findings in these lesions include pain, swelling, and joint blockage. The study, which includes radiographs in anteroposterior (AP), lateral, and axial projections of the knee at 30°, is part of the initial study in the diagnostic process, which can yield a negative result in up to 36% of cases.[2] In the case described, CT had fundamental value in making the proper diagnosis and planning the surgical treatment. Magnetic resonance imaging (MRI) allows us to visualize osteochondral fragments, edema, and joint effusion that radiography may omit; in addition, it may show injuries to other intra- or extra-articular structures, which are important for defining treatment.[1]

Surgical treatment consists of fixation of the fragments, especially if they are large and belong to loading zones, the goal should be anatomic reduction and stable fusion, to allow early rehabilitation of the knee. The surgical technique is based on the fixation of osteochondral fragments in the joint, with different types of osteosynthesis and the medial patellofemoral ligament reconstruction (MPFLR).[1]

Case Report

A 15-year-old female patient, with no past medical history, suffered a forced valgus injury of the left knee, evolving with pain and functional impairment. On physical examination, painful standing, joint effusion, and pain in the anterior aspect of the left knee were observed, with limitation of flexion to 50–60°. Stability and meniscal tests could not be assessed. A knee X-ray was performed, showing an intra-articular fragment. A CT scan of the knee revealed an osteochondral fracture of the left patella with an intra-articular loose body larger than 1 cm². The case was managed surgically by means of a medial parapatellar approach, arthrotomy with drainage of hematic content, identification of the intra-articular loose body, and the osteochondral fracture on the medial articular facet. After regularization of both components, reduction and osteosynthesis were performed with three 1.3 mm mini-fragment cortical screws (Compact Hand, Synthes®) in a triangular arrangement ([Fig. 1]), achieving anatomic reduction. MPFLR was performed with semitendinosus using a loop to the abductor tendon, obtaining a good radiological and functional outcome ([Fig. 2]). The patient had no other signs of patellar instability requiring treatment. She has an uncomplicated postoperative course; no immobilization was used, and ambulation with crutches was allowed on discharge of the operated limb. Kinesis rehabilitation begins at 6 weeks post-surgery, starting with partial support. At 8 weeks, she was walking without assistance, and, at 6 months, she was asymptomatic, gradually recovering from her physical activities. Kujala Patellofemoral Pain Scale 100 points at 6 months.

Fig. 1 Intraoperative photograph showing the posterior surface of the left patella with the osteochondral fragment fixed with three cortical screws.

Fig. 2 (A) Axial radiograph of the patella and (B) lateral radiograph of the left knee obtained as postoperative controls, demonstrating adequate reduction and fixation of the osteochondral fragment.

Discussion

Osteochondral fractures (OCF) are those that affect the articular cartilage partially or totally, with extension to the subchondral bone. They are more common in injuries in children, adolescents, and young adults, as at these ages the layer of calcified cartilage is not yet mature, facilitating injury between the articular cartilage and subchondral bone. Knee OCFs is the most common and can occur on the lateral aspect of the femoral condyle, the inferior aspect of the medial ridge of the patella, and the inferior medial facet of the patella.[3]

OCFs usually occur in the context of a patellar dislocation (PD), because of low-energy trauma or sports injuries in adolescents, then a valgus mechanism with axial loading and rotation with the knee extended, consistent with the presented case.[4]

OCF is due to the impact between the lateral femoral condyle and the medial facet of the patella. This impact generates damage to the joint cartilage, synovial membrane, subchondral bone, and infra patellar fat, contributing to the development of osteoarthritis. Its location in these cases will be medial and associated with injuries of the medial patellar femoral ligament (MPFL) or medial retinaculum.[4]

A recent systematic review published by Lei Zheng et al. found a higher risk of OCF after a first episode of PD in men who have reached bone maturity, with a trochlea without anatomic alterations and complete lesions of the MPFL.[5]

Moreover, in patients with previous episodes of PD, up to 76% incidence of OCF is reported, resulting in the loss of joint congruence with early patellofemoral osteoarthritis and maintaining the cycle of recurrent instability. The mechanism of production of these OCF is often produced by shear forces between the patella and femur, resulting from the initial dislocation or its reduction, commonly affecting the medial facet of the patella, consistent with the presented case.[4]

OCFs without prior dislocation are uncommon and usually affect the medial center facet of the patella. Due to the absence of dislocation, a high index of suspicion is needed and should be raised when pain, shedding, and/or joint lockout persist.[1]

Regarding its clinical presentation, it is uncommon for the patient to come with a dislocated patella to the emergency room; usually, on mobilization, it shrinks. On physical examination, there may be hemarthrosis, whose main cause in adolescents is PD. We can also find joint blockage, which is both parts of the diagnosis in our case.[1] [2]

The initial study with knee radiographs in AP, lateral, and axial patellar views at 30° can provide important diagnostic information; we may visualize the PD if present, signs of hemarthrosis, or an intra-articular loose body ([Fig. 3]), as well as establish a differential diagnosis. In the case described, CT was fundamental to confirm the diagnosis and to plan the surgical treatment ([Fig. 4]).

Fig. 3 (A) Axial radiograph of the patella and (B) lateral radiograph of the left knee showing an intra-articular fragment.

Fig. 4 (A) Axial and (B) sagittal CT cans of the left knee showing a patellar fracture on the medial articular facet with the presence of an intra-articular fragment.

The study with MRI that allows us to see osteochondral fragments, edema, joint swelling, and injury of the MPFL that X-ray can omit, helps us to differentiate OCL from OCF. In addition, it can show lesions in other intra- or extra-articular structures, important for defining treatment, as well as anatomic parameters related to patellar instability.[2] [4] In the case of children, who do not know whether they have suffered a dislocation and whose injury makes physical examination difficult, it is useful to diagnose acute PD.[4]

PD as a first episode, without severe OCL or signs of recurrent patellar instability and with proper alignment on imaging studies, is usually treated conservatively; the occurrence of OCL has been considered in selected cases as a justification for surgery after an acute PD.[6]

Regarding treatment, the goal in the primary phase is to reduce and stabilize the OCF, restore articular cartilage, and stabilize the patella to prevent chronic instability. Management will depend on the size of the fragment, the location of the injury (whether it is a weight-bearing area or not), and its extent, as well as patient characteristics.[3]

There is unanimity in the literature regarding the recommendation for conservative treatment in fragments smaller than 1 cm², located on the external edge of the patellofemoral surface, with few symptoms, since it has been shown that chondral lesions with a diameter greater than 10 mm accelerate cartilage degeneration.[1] [2] [3] [4] This includes rest, anti-inflammatory drugs, and immobilization.[3]

Mikko Uimonen et al published a case series of 73 patients, where 46% were treated conservatively with small OCF (< 1 cm2) located on the outer edge of the patellofemoral surface. Of this group 30% required late surgery, most of which was MPFLR or treatment for recurrent patellar instability.[6]

Fragments larger than 1 cm² in the central area of the articular surface are treated surgically, seeking to fix the osteochondral fragments in the joint. The fixation methods described vary; metallic implants such as Kirschner wires, cannulated screws, and headless screws, among others, are described. Bioabsorbable implants such as smartnails, polyetheretherketone implants, poly-L-lactic acid, and tissue adhesives are also described, which can also be used in this type of injury.[3] [4] [5] [6] [7]

When it is not possible to fix them, the free body can be removed, especially when it is located on the external edge of the patellofemoral surface.[3]

There are a few long-term comparative studies of different types of fixations. Metallic screws provide better compression and stability, but they can cause abrasive wear of the articular surface, may require removal, and make imaging, such as MRI, difficult to interpret. Bioabsorbable implants do not present these disadvantages, but they are associated with less compression, and cyst formation has been reported because of their rapid absorption. Furthermore, the possibility of an allergic reaction must be considered.[7]

A retrospective study published by Jaroslaw Felus et al. in adolescent patients with OCF secondary to PD analyzed 42 OCFs. All but three were treated with absorbable trans-osseous sutures, presenting a 100% cure rate confirmed by MRI with favorable mid-term outcomes. The use of absorbable trans-osseous sutures provides sufficient compression and stability to allow early range-of-motion exercises.[7]

MPFLR, along with OCF fixation, has become a trend in the last decade to prevent recurrent patellar instability. Studies show that failure to address instability increases the likelihood of failure and the need for additional surgeries. Therefore, it is recommended that primary causes of instability, such as dysplasia or malalignment, also be treated with patellar stabilization or alignment procedures to improve overall outcomes.[1] This reconstruction is performed using different techniques, primarily autografts (semitendinosus, gracilis, or quadriceps), allografts, or synthetic grafts, with a focus on anatomical techniques that respect the biomechanics of the joint. Currently, there is no evidence regarding the best type of graft or femoral and patellar fixation device, with similar results reported with each technique.[8]

We recommend treating the primary causes of patellar instability if present to avoid suboptimal results in any OCF management technique.

Conclusion

Patellar OCFs after a first episode of dislocation should be suspected when pain, effusion, and/or joint blockage persist even after the dislocation has been reduced. Diagnostic workup should include a CT scan, as the bone fragment is often not visible on X-rays. The workup can be completed with an MRI to evaluate associated injuries. Treatment is key, as OCFs are injuries that affect the integrity of the joint surface and have a high degenerative potential.[3]

Conflict of Interest

None declared.

• Referencias

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• 3 Cordunianu MA, Antoniac I, Niculescu M. et al. Treatment of knee osteochondral fractures. Healthcare (Basel) 2022; 10 (06) 1061
• 4 Tuca M, Pineda T, Nuñez M, Zilleruelo N, Olmedo C, Figueroa D. Patrones de lesión en resonancia magnética de un primer episodio de luxación patelar en niños y adolescentes. Revista Chilena de Ortopedia y Traumatología 2022
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• 8 Monaco E, Criseo N, Annibaldi A. et al. Medial patellofemoral ligament reconstruction using gracilis tendon graft and “all suture” knotless anchors for patellar fixation. Arthrosc Tech 2023; 12 (12) e2329-e2334

Publication History

Received: 20 May 2025

Accepted: 02 September 2025

Article published online:
22 December 2025