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Trochlear dysplasia and trochleoplasty

61 citationsUpdated Sep 2026

Overview

Trochleoplasty surgically corrects the pathological features of trochlear dysplasia by creating more normal anatomy, allowing the trochlea to be restored to a normal or nearly normal state [2]. This procedure is indicated as a first-line treatment for objective patellar instability associated with high-grade dysplasia, or for recurrence in high-grade dysplasia previously managed by other surgery [24]. It is also indicated in the setting of severe trochlear dysplasia, where sulcus-deepening trochleoplasty provides a reliable solution to recurrent patellar instability [50]. Trochlear dysplasia is a major risk factor for the failure of operative stabilization, suggesting that tailored therapy including MPFL reconstruction and trochleoplasty should be considered [9]. In selected adolescent patients with severe or high-grade trochlear dysplasia, the procedure can be safely performed up to two years before the projected end of growth, with no growth disturbance occurring after surgery for recurrent patellar dislocation in those with open growth plates [6, 10].

Clinical outcomes are generally favorable, with patients experiencing significant postoperative improvement and achieving equivalent outcomes whether trochleoplasty is performed as an index procedure or as a revision following a prior failed patellar stabilizing procedure [12]. Satisfying subjective long-term outcomes can be expected, and no patient developed grade 3 or 4 osteoarthritis, supporting the procedure as a reliable surgical option for high-grade dysplasia [4, 5]. Favorable patient-reported outcomes are achieved at final follow-up in patients treated for patellofemoral instability with severe trochlear dysplasia [23]. However, trochleoplasty is a technically demanding technique requiring careful patient selection, detailed knowledge, and surgical skills to avoid severe complications [35]. Complication rates are similar to other patellar-stabilizing procedures [13], although significantly more patients who underwent trochleoplasty showed a decline in trochlear chondral status at short-term to midterm follow-up [11].

While trochleoplasty provides good clinical outcomes and an acceptable complication profile in both short and long-term follow-up [7], it should not be performed as a secondary or revision procedure but rather as a primary procedure with clear indications [15]. Although failure rates were highest after isolated trochleoplasty and complication rates were highest after tibial tubercle osteotomy, these procedures are not interchangeable as each addresses a specific pathology [16]. In patients with severe trochlear dysplasia, a combination surgery including trochleoplasty resulted in the greatest improvement [3]. Further research is needed to refine indications and compare long-term outcomes to other patellar stabilizing surgeries in patients with severe trochlear dysplasia [1].

Anatomy & Pathophysiology

Bony Anatomy

The trochlear groove separates the femoral condyles anteriorly and constitutes the patellofemoral articulation [55]. The lateral trochlear facet resists lateral subluxation of the patella [69]. A transverse ridge known as the sulcus terminalis extends from the oblique facets of the femoral trochlea, presenting a depth that is greater on the lateral condyle than on the medial condyle [69]. The patella, the largest sesamoid bone in the body, averages 2.5 cm in thickness [55]. Its articular surface is the thickest in the body, measuring approximately 5 mm in the midportion and 2 mm on the sides [55]. A vertical, central ridge divides the patellar articular surface into a broader lateral facet and a medial facet, with a smaller, more medial facet termed the odd facet [55].

Soft Tissue Stabilizers

The medial patellofemoral ligament (MPFL) serves as the most important static medial patellar stabilizer, contributing more than 50% to stability [119]. It runs from the patella near the junction of the middle and superior thirds to the medial femoral epicondyle [58]. The meshing of the MPFL with the vastus medialis obliquus dynamizes the ligament during initial flexion [119]. Extraarticular static stability is principally provided by the joint capsule and collateral ligaments [58]. The anteromedial and anterolateral portions of the knee capsule are reinforced by the medial and lateral patellar retinacular expansions [58].

Pathophysiology of Instability

Patellar instability is a multifactorial condition where the dynamic interplay of osseous and soft-tissue abnormalities creates an imbalance of forces about the extensor mechanism, allowing the patella to dislocate laterally [136]. Trochlear dysplasia is related to malalignment of the extensor mechanism and can result in patellar dislocation [141]. The shape alteration of the trochlear groove is the main risk factor for patellar instability, present in up to 96% of patients with recurrent patellar dislocations [41]. In patients who have undergone previous patellar stabilization procedures, trochlear dysplasia is the most impactful risk factor contributing to recurrent patellar instability [136]. The position of the trochlear groove relative to the tibial tubercle is abnormal in knees with patellofemoral instability, indicating malalignment of the extensor mechanism [141]. Conversely, a laterally positioned concave trochlear groove prevents patellar dislocation [141].

In a cohort of patients undergoing MPFL reconstruction, 14% had no trochlear dysplasia, 51% had Dejour type A dysplasia, and 35% had types B to D dysplasia [22]. Surgical management designed to realign the extensor mechanism and balance soft tissues may fail to address patellar instability driven by severe trochlear dysplasia if the dysplasia is not corrected [136]. Performing MPFL reconstruction or tibial tubercle osteotomy without addressing severe trochlear dysplasia can cause an overload on the patellofemoral compartment, resulting in increased pain, range of motion restriction, and osteoarthritis progression [41]. Deepening trochleoplasty is indicated for patients with high-grade trochlea dysplasia [21].

Classification

Oswestry-Bristol Classification: The Oswestry-Bristol Classification (OBC) is used to assess the severity of trochlear dysplasia [30]. Within this framework, types B and D are characterized by the presence of a supratrochlear spur, while types A and C are characterized by the absence of a supratrochlear spur [52].

Cranial Trochlear Orientation: A new system for characterizing trochlear morphology divides axial trochlear shape into two types based on the most cranial trochlear orientation [33]. A positive CTO indicates that the trochlea serves as a medial barrier, whereas a negative CTO indicates that the trochlea serves as a lateral barrier [33].

Other Considerations: The entry point-trochlear groove angle is a measurement technique that describes the lateralization of the proximal trochlear entry point in patients with patellar instability [27]. This measurement technique requires further refinement and validation before it can be widely used at the clinical level [27]. In an international multicenter study of medial patellofemoral ligament reconstruction, 14% of patients had no trochlear dysplasia, 51% had Dejour type A dysplasia, and 35% had types B to D dysplasia [22]. In a cohort of 171 patients undergoing medial patellofemoral ligament reconstruction, 5 patients (2.9%) were excluded due to high-grade trochlear dysplasia [31]. In a study of skeletally immature patients with patellar dislocation, the surgical group had a baseline proportion of 18.8% normal type A trochlea and 81.2% high-grade trochlear dysplasia, while the nonsurgical group had 34.2% normal type A and 65.8% high-grade dysplasia [131]. At final follow-up in skeletally immature patients, the proportion of normal type A trochlea was significantly higher in the surgical group (68.7%) than in the nonsurgical group (46.4%) [131].

Clinical Presentation

Trochlear dysplasia is a major risk factor for the failure of operative stabilization for patellar instability [9]. It also serves as a preoperative risk factor for failure when medial patellofemoral ligament (MPFL) reconstruction is combined with tibial tubercle osteotomy and lateral retinacular release [29]. In the context of Insall's proximal realignment, trochlear dysplasia was a significant risk factor for the development of patellofemoral osteoarthritis, whereas recurrent patellar instability was not [48]. The Oswestry-Bristol Classification can be used to assess the severity of trochlear dysplasia [30].

In a multicenter study of isolated MPFL reconstruction, 14% of patients had no trochlear dysplasia, 51% had Dejour type A dysplasia, and 35% had types B to D dysplasia [22]. Acceptable outcomes were observed for isolated MPFL reconstruction regardless of the degree of trochlear dysplasia in an international multicenter study [22]. Similarly, the presence of severe trochlear dysplasia did not compromise functional results in patients undergoing isolated MPFL reconstruction for recurrent patellar dislocations with increased femoral anteversion and an absent or mild J-sign [19].

Patients with more severe trochlear pathology required more time to return to sports following tibial tubercle anteromedialization with MPFL reconstruction [25]. Female gender was a risk factor for worse postoperative outcomes in patients undergoing MPFL reconstruction combined with tibial tubercle osteotomy and lateral retinacular release [29].

In a cohort of patients undergoing grooveplasty or trochleoplasty, 79% were female and the mean age at the initial instability event was 11.8 years [26]. The mean age at the time of the procedure was 21.3 years [26]. Additionally, 65% of these patients had more than 10 lifetime instability events [26]. Four trochleoplasty patients in a comparative cohort had documented hypermobility compared with no patients in the grooveplasty cohort [26].

Excessive or insufficient patellar loading leads to trochlear dysplasia in an experimental rat model [46].

Investigations

Imaging and Classification

Plain radiography: Patellofemoral radiographic views assess patellofemoral alignment, patellar and trochlear morphology, osteochondral injury, and patellofemoral arthritis [73]. A new measurement technique involving the entry point-trochlear groove angle may describe trochlear dysplasia in a new way, but further refinement and validation are required before it can be widely used at the clinical level [27].

CT: Three-dimensional CT with remodeling is used for preoperative planning for reconstruction associated with dysplasia [81]. CT changes after trochleoplasty demonstrate that the procedure can correct the pathological features of trochlear dysplasia by surgically creating more normal anatomy [2].

MRI: Five-year MRI follow-up shows that trochlea dysplasia can be corrected to normal or nearly normal trochlea [4]. Postoperative MRI after trochleoplasty revealed no chondrolysis or subchondral necrosis, but deterioration of cartilage on the lateral trochlear facet was identified [52].

Other Considerations: According to a new system based on the most cranial trochlear orientation, axial trochlear shape may be divided into two types: a positive CTO and a negative CTO, with the trochlea serving, respectively, as a medial and lateral barrier [33]. Deepening trochleoplasty and medial patellofemoral ligament reconstruction normalize patellotrochlear congruence in severe trochlear dysplasia [53]. Improvements in trochlear shape and patient-reported outcomes after arthroscopic deepening trochleoplasty and medial patellofemoral ligament reconstruction corresponded to those obtained by open trochleoplasty [18].

Associated Pathology and Risk Factors

Trochlear dysplasia is a major risk factor for failure of operative stabilization for patellar instability in children with open growth plates [9]. It was a significant risk factor for osteoarthritis development after Insall's proximal realignment, whereas recurrent patellar instability was not [48]. Patients with high-grade trochlear dysplasia show significantly increased sagittal tibial tubercle trochlear-groove distance compared with patients without trochlear dysplasia [134]. The trochlear groove is almost 9mm more anterior to the tibial tuberosity in patients with symptomatic instability, and this distance correlates with measurements of trochlear dysplasia [137]. Excessive or insufficient patellar loading leads to trochlear dysplasia [46].

Postoperative Imaging and Tissue Viability

The tissue in the trochlear groove remained viable after trochleoplasty, with cartilage retaining a distinctive hyaline architecture [54].

Treatment

Non-Operative

The provided evidence does not detail specific conservative management protocols such as weight loss, physical therapy, or pharmacological interventions. Surgical management is indicated for patients in the second and third decades of life practising contact sports, and for those presenting with types C and D trochlea dysplasia and patella alta [51].

Operative

Indications: Trochleoplasty is indicated for patients with severe or high-grade trochlear dysplasia in the context of patellofemoral instability [23, 42, 98]. It is specifically recommended for patients with severe trochlear dysplasia and recurrent patellar dislocation or instability, particularly when benign neglect would lead to unfavourable results [17, 39, 47]. The procedure is also indicated for painful instability with a major dysplastic trochlea or in revision cases when other procedures have failed [108]. For patients with high-grade trochlear dysplasia and lateral patellofemoral instability, trochleoplasty is an acceptable treatment [7]. When performed as a solitary treatment for recurrent patellofemoral dislocations in patients with trochlear dysplasia, good clinical outcomes are achieved if severe torsional and axial malalignment is excluded [32].

Surgical Approach / Technique: Several techniques are described for trochleoplasty. Bereiter trochleoplasty is a surgical technique used for high-grade trochlea dysplasia [42]. Deepening trochleoplasty is carried out in patients with high-grade trochlea dysplasia [21]. Recession wedge trochleoplasty is a simple and safe procedure that provides patellofemoral stability and pain relief [108]. Trochleoplasty performed using a flexible osteochondral flap is an effective treatment for recurrent patellar instability in patients with severe trochlea dysplasia, yielding good medium-term results [47]. Thin flap trochleoplasty combined with medial patellofemoral ligament reconstruction serves as a treatment strategy for recurrent patellofemoral instability with high-grade trochlear dysplasia [39]. Arthroscopic deepening trochleoplasty combined with medial patellofemoral ligament reconstruction yields improvements corresponding to those obtained by open trochleoplasty [18]. Grooveplasty is a surgical procedure for the treatment of trochlear dysplasia in the setting of patellar instability [26].

Combined Procedures and Adjuncts: A combination surgery including trochleoplasty resulted in the greatest improvement in cases of severe trochlear dysplasia [3]. Trochleoplasty with concomitant medial patellofemoral ligament reconstruction is an effective and safe treatment option for patellofemoral instability in the setting of high-grade trochlear dysplasia [98]. Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia [8]. Even patients with high-grade trochlear dysplasia showed satisfactory results with this derotational distal femur osteotomy and medial patellofemoral ligament reconstruction combination, and additional surgery is not necessary for those patients [8].

Outcomes and Complications: Bereiter trochleoplasty for high-grade trochlea dysplasia reports a very low redislocation rate of 1.1% and good clinical outcomes at two-year follow-up [42]. Recession wedge trochleoplasty is effective to provide patellofemoral stability and pain relief in cases of painful instability with a major dysplastic trochlea or in revision cases when other procedures have failed [108]. Trochleoplasty is a viable option for patellar instability in patients with severe trochlear dysplasia [50]. A systematic review showed significant postoperative improvements both in patients undergoing trochleoplasty procedures and in patients undergoing nontrochleoplasty procedures for the treatment of patellar instability caused by severe trochlear dysplasia [142]. Grooveplasty patients had less recurrent instability, and similar patient-reported outcomes and reoperation rates compared to trochleoplasty [34]. Good patient satisfaction with a low complication rate is observed after trochleoplasty in patellofemoral instability [35].

Other Considerations: For selected adolescent patients with high-grade trochlear dysplasia, trochleoplasty can be safely performed up to 2 years before the projected end of growth [10]. Trochleoplasty as a solitary treatment for recurrent patellofemoral dislocations in adolescents with trochlear dysplasia resulted in good clinical outcomes [32]. The procedure provides favorable patient-reported outcomes in patients with patellofemoral instability and severe trochlear dysplasia at a minimum 2-year follow-up [23]. Trochlear dysplasia is a major risk factor for failure of operative stabilization, suggesting that tailored therapy including MPFL reconstruction and trochleoplasty should be considered in children with open growth plates [9]. Further research is needed to refine indications and compare long-term outcomes to other patellar stabilizing surgeries in adolescent patients with severe trochlear dysplasia [1].

Complications

Cartilage and Arthritis: Trochleoplasty is associated with high rates of patellofemoral arthritis [45] and worsens the natural course of patellofemoral arthritis in the long term [45]. In a retrospective cohort study of sulcus-deepening trochleoplasty, no patient developed grade 3 or 4 osteoarthritis [5]. However, significantly more patients who underwent trochleoplasty showed a decline in trochlear chondral status at short-term to midterm follow-up compared to controls [11].

Instability and Failure: Isolated trochleoplasty had the highest failure rates among patellar stabilizing procedures in a systematic review [16]. Trochlear dysplasia was identified as a preoperative risk factor for failure in patients undergoing MPFL reconstruction combined with tibial tubercle osteotomy and lateral retinacular release [29]. Grooveplasty patients had less recurrent instability compared to trochleoplasty patients [34].

General Complication Rates: Trochleoplasty provides an acceptable complication profile in both short and long-term follow-up [7]. Isolated tibial tubercle osteotomy (TTO) had the highest complication rates among patellar stabilizing procedures in a systematic review [16].

Adolescent-Specific Complications: No growth disturbance was observed after trochleoplasty for recurrent patellar dislocation in adolescents with open growth plates [6].

Recovery

Light activity (weeks): The provided evidence does not specify a typical week range for light activity, desk work, driving, or light ADLs.

Full activity (months): The provided evidence does not specify a month range for full activity, manual work, or sport.

Complete recovery / outcome plateau (months): The provided evidence does not specify a month range for complete recovery or outcome plateau.

Rehabilitation protocol: The provided evidence does not detail specific PT phasing, immobilisation duration, weight-bearing/ROM progression, or sling/brace removal timing.

Functional milestones: Favorable patient-reported outcomes (PROs) were achieved at final follow-up in patients who underwent trochleoplasty for patellofemoral instability with severe trochlear dysplasia [23]. Improvements corresponded to those obtained by open trochleoplasty [18]. Deepening trochleoplasty with a thick flap improves clinical and functional outcomes for patients with symptomatic patellar instability with severe trochlear dysplasia [43]. Sulcus deepening trochleoplasty corrects patellofemoral stability even in patients with severe dysplasia, and the long-term functional outcome is better in this group [109].

Other Considerations: Cartilage and Joint Health: Tissue in the trochlear groove remained viable after trochleoplasty, with cartilage retaining a distinctive hyaline architecture [54]. No patient developed grade 3 or 4 osteoarthritis (OA), supporting trochleoplasty as a reliable surgical option for patients with high-grade trochlear dysplasia [5]. The development of patellofemoral osteoarthritis at 12-year follow-up did not exceed the findings from other trochleoplasty case series [147].

Clinical Outcomes and Stability: European centers have published the majority of data on this procedure, which is shown to be acceptable for patients with high-grade trochlear dysplasia and lateral patellar instability (LPI) [7]. Even patients with high-grade trochlear dysplasia showed satisfactory results, and additional surgery is not necessary for those patients [8]. The presence of severe trochlear dysplasia did not compromise functional results [19].

Complications and Risks: The study provides clinicians with the best currently available evidence on the rate of complications after trochleoplasty procedures to help inform patient decisions [13]. Trochlear dysplasia is a major risk factor for failure of operative stabilization, suggesting that tailored therapy including medial patellofemoral ligament (MPFL) reconstruction and trochleoplasty should be considered [9]. Age and trochlear dysplasia were preoperative failure risk factors [29]. Female gender was a risk factor for worse postoperative outcomes [29].

Return to Activity: Patients with more severe trochlear pathology required more time to return to sports [25].

Key Evidence

  • [L4] Further research is needed to refine indications and compare long-term outcomes to other patellar stabilizing surgeries in patients with severe trochlear dysplasia. [1] (10.1177/2325967126s00135)
  • [L4] Trochleoplasty can correct the pathological features of trochlear dysplasia by surgically creating more normal anatomy. [2] (10.1007/s00167-006-0140-8)
  • [L4] In particular, a combination surgery including trochleoplasty resulted in the greatest improvement in case of severe trochlear dysplasia. [3] (10.1016/j.otsr.2018.01.003)
  • [L4] Trochlea dysplasia can be corrected to normal or nearly normal trochlea, and satisfying subjective long-term outcomes can be expected. [4] (10.1016/j.jisako.2023.03.314)
  • [L3] No patient developed grade 3 or 4 OA, supporting trochleoplasty as a reliable surgical option for patients with high-grade trochlear dysplasia. [5] (10.1177/23259671251405283)
  • [L4] Therefore, in selected adolescent patients with severe trochlear dysplasia trochleoplasty can be safely performed up to two years before the projected end of growth. [6] (10.1177/2325967119s00221)
  • [L1] European centers have published the majority of data on this procedure, which is shown to be acceptable for patients with high-grade trochlear dysplasia and LPI. [7] (10.1007/s00167-018-5311-x)
  • [L3] Even patients with high-grade trochlear dysplasia showed satisfactory results, and additional surgery is not necessary for those patients. [8] (10.1007/s00167-023-07476-y)
  • [L3] Trochlear dysplasia is a major risk factor for failure of operative stabilization, suggesting that tailored therapy including MPFL reconstruction and trochleaplasty should be considered. [9] (10.1007/s00167-011-1599-5)
  • [L4] Therefore, for selected adolescent patients with high-grade trochlear dysplasia, trochleoplasty can be safely performed up to 2 years before the projected end of growth. [10] (10.1177/0363546518794671)
  • [L3] Yet, significantly more patients who underwent trochleoplasty showed a decline in trochlear chondral status at short-term to midterm follow-up. [11] (10.1177/23259671251326052)
  • [L3] Patients with severe trochlear dysplasia will experience significant improvement postoperatively and will have equivalent outcomes if a trochleoplasty is performed as an index procedure or as a revision procedure following a prior failed patellar stabilizing procedure. [12] (10.1177/2325967117s00388)
  • [L1] The study provides clinicians with the best currently available evidence on the rate of complications after trochleoplasty procedures to help inform patient decisions. [13] (10.1007/s00167-017-4766-5)
  • [L5] Trochleoplasty should not be performed as a secondary or revision procedure but rather as a primary procedure with clear indications. [15] (10.1016/j.arthro.2020.05.050)
  • [L1] Although failure rates were highest after isolated trochleoplasty and complication rates were highest after TTO, these procedures are not interchangeable as each addresses a specific pathology. [16] (10.1016/j.arthro.2024.05.019)
  • [L4] Recent bibliography presents very encouraging results from the application of trochleoplasty with other procedures in a selected population with severe trochlear dysplasia and recurrent patellar dislocation, in whom benign neglect would lead to unfavourable results. [17] (10.1007/s00167-014-3013-6)
  • [L4] The improvements corresponded to those obtained by open trochleoplasty. [18] (10.1177/23259671231171378)
  • [L3] Crucially, the presence of severe trochlear dysplasia did not compromise functional results. [19] (10.1177/03635465261437776)
  • [L2] [21] (10.1186/s13018-021-02513-3)
  • [L3] [22] (10.1016/j.jisako.2025.101028)
  • [L3] Furthermore, at final follow-up favorable PROs were achieved in patients who underwent trochleoplasty for the treatment of their patellofemoral instability with severe trochlear dysplasia. [23] (10.1177/23259671251321499)
  • [L5] Trochleoplasty is indicated in first line for objective patellar instability associated with high-grade dysplasia or for recurrence in high-grade dysplasia previously managed by other surgery. [24] (10.1016/j.otsr.2021.103160)
  • [L3] Patients with more severe trochlear pathology required more time to return to sports. [25] (10.1002/ksa.12051)
  • [L3] [26] (10.1016/j.asmr.2022.11.020)
  • [L5] Although this new measurement technique is promising and may describe trochlear dysplasia in a new way, further refinement and validation are required before it can be widely used at the clinical level. [27] (10.1016/j.arthro.2024.06.005)
  • [L4] Female gender was a risk factor for worse postoperative outcomes, while age and trochlear dysplasia were preoperative failure risk factors. [29] (10.1186/s12891-021-04508-x)
  • [L4] The OBC can be used to assess the severity of trochlear dysplasia. [30] (10.1302/0301-620x.102b1.bjj-2019-0366.r3)
  • [L3] [31] (10.1016/j.arthro.2023.07.006)
  • [L4] Trochleoplasty as a solitary treatment for recurrent patellofemoral dislocations in patients with trochlear dysplasia resulted in good clinical outcomes if severe torsional and axial malalignment was excluded. [32] (10.1177/0363546516652894)
  • [L3] According to this new system, the axial trochlear shape may be divided into two types: a positive CTO and a negative CTO, with the trochlea serving, respectively, as a medial and lateral barrier. [33] (10.1002/ksa.12314)
  • [L3] Grooveplasty patients had less recurrent instability, and similar patient reported outcomes and reoperation rates compared to trochleoplasty. [34] (10.1016/j.arthro.2023.08.056)
  • [L5] Trochleoplasty is a technically demanding technique requiring careful patient selection, detailed knowledge, and surgical skills to avoid severe complications. [35] (10.1007/s00167-022-06954-z)
  • [L4] [39] (10.1177/03635465251314882)
  • [L5] [41] (10.1016/j.eats.2023.04.030)
  • [L4] The study reports a very low redislocation rate of 1.1% and good clinical outcomes at two-year follow-up after Bereiter trochleoplasty for high grade trochlea dysplasia. [42] (10.1002/ksa.12663)
  • [L4] Deepening trochleoplasty with a thick flap improves clinical and functional outcomes for patients with symptomatic patellar instability with severe trochlear dysplasia. [43] (10.1177/0363546515597679)
  • [L4] Trochleoplasty worsens the natural course of patellofemoral arthritis in the long term. [45] (10.1002/ars2.70021)
  • [L5] Excessive or insufficient loading leads to trochlear dysplasia. [46] (10.1186/s13018-023-03500-6)
  • [L3] Trochleoplasty performed using a flexible osteochondral flap is an effective treatment for recurrent patellar instability in patients with severe trochlea dysplasia and gives good results in the medium term. [47] (10.1302/0301-620x.99b3.37884)
  • [L4] Trochlear dysplasia was a significant risk factor for osteoarthritis development, whereas recurrent patellar instability was not. [48] (10.1007/s00167-013-2485-0)
  • [L4] When indicated in the setting of severe trochlear dysplasia, sulcus-deepening trochleoplasty can provide a reliable and successful surgical solution to recurrent patellar instability. [50] (10.1177/2325967117s00389)
  • [L4] Surgical management should be performed in patients in the second and third decades of life practising contact sports and in those patients who present types C and D trochlea dysplasia and patella alta. [51] (10.1007/s00167-022-07273-z)
  • [L3] [52] (10.1007/s00167-011-1410-7)
  • [L3] Modifying the dysplastic trochlea involves approximating the trochlear morphology to the shape of the patella rather than inducing a patella and trochlea mismatch. [53] (10.1302/0301-620x.101b3.bjj-2018-0795.r2)
  • [L4] The tissue in the trochlear groove remained viable after trochleoplasty, with cartilage retaining a distinctive hyaline architecture. [54] (10.1007/s00167-006-0148-0)
  • [L4] Trochleoplasty with concomitant medial patellofemoral ligament reconstruction is an effective and safe treatment option for patellofemoral instability in the setting of high-grade trochlear dysplasia. [98] (10.1002/ksa.70043)
  • [L4] Recession wedge trochleoplasty is a simple and safe procedure that seems effective to provide patellofemoral stability and pain relief in cases of painful instability with a major dysplastic trochlea or in revision cases when other procedures have failed. [108] (10.1016/j.otsr.2011.07.013)
  • [L4] Sulcus deepening trochleoplasty corrects patellofemoral stability even in patients with severe dysplasia and the long-term functional outcome is better in this group. [109] (10.1016/j.otsr.2015.01.017)
  • [L5] The medial patellofemoral ligament is the most important static medial patellar stabilizer, contributing more than 50% to stability, and its meshing with the vastus medialis obliquus dynamizes the ligament during initial flexion. [119] (10.1007/s00167-005-0631-z)
  • [L3] [131] (10.1177/03635465241301775)
  • [L3] Patients with high-grade trochlear dysplasia show not only abnormal values in common patellofemoral instability risk factors but also a significantly increased sagittal tibial tubercle trochlear-groove distance compared with patients without trochlear dysplasia. [134] (10.1016/j.arthro.2024.05.023)
  • [L4] [136] (10.1016/j.jisako.2025.100387)
  • [L3] The trochlear groove is almost 9mm more anterior to the tibial tuberosity in patients with symptomatic instability, and this distance correlates with measurements of trochlear dysplasia. [137] (10.1177/2325967117s00383)
  • [L2] [141] (10.1097/01.blo.0000203478.27044.9a)
  • [L1] This systematic review showed significant postoperative improvements both in patients undergoing the trochleoplasty procedures and in patients undergoing the nontrochleoplasty procedures for the treatment of patellar instability caused by STD. [142] (10.1016/j.arthro.2014.01.011)
  • [L4] In contrast to general belief, the development of patellofemoral osteoarthritis at 12-year follow-up did not exceed the findings from other trochleoplasty case series. [147] (10.1007/s00167-017-4602-y)

See Also

References

[1] Gettin' in the Groove: Characterizing the Trochleoplasty Learning Curve in Adolescent Patients with Patellofemoral Instability. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/2325967126s00135

[2] CT changes after trochleoplasty for symptomatic trochlear dysplasia. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0140-8

[3] Patellofemoral reconstruction for patellar instability with patella alta in middle-aged patients: Clinical outcomes. Orthopaedics & Traumatology: Surgery & Research. 2018. DOI: 10.1016/j.otsr.2018.01.003

[4] Trochlear Morphology and Cartilage Viability After Mini-Open Lateral Approach Trochleaplasty for Patellar Dislocation – 5 Year MRI Follow-Up Study. Journal of ISAKOS. 2023. DOI: 10.1016/j.jisako.2023.03.314

[5] Long-Term Clinical Impact of Radiographic Patellofemoral Osteoarthritis After Sulcus-Deepening Trochleoplasty: A Retrospective Cohort Study. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/23259671251405283

[6] No growth disturbance after trochleoplasty for recurrent patellar dislocation in adolescents with open growth plates. Orthopaedic Journal of Sports Medicine. 2019. DOI: 10.1177/2325967119s00221

[7] Trochleoplasty provides good clinical outcomes and an acceptable complication profile in both short and long-term follow-up. Knee Surgery, Sports Traumatology, Arthroscopy. 2018. DOI: 10.1007/s00167-018-5311-x

[8] Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia. Knee Surgery, Sports Traumatology, Arthroscopy. 2023. DOI: 10.1007/s00167-023-07476-y

[9] Analysis of failed surgery for patellar instability in children with open growth plates. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1599-5

[10] No Growth Disturbance After Trochleoplasty for Recurrent Patellar Dislocation in Adolescents With Open Growth Plates. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518794671

[11] Influence of Sulcus-Deepening Trochleoplasty on Patellofemoral Cartilage Integrity in Patients With Severe Trochlear Dysplasia at Short-term to Midterm Follow-up: A Case-Control Study. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251326052

[12] Equivalent Outcomes for Patients Following Trochleoplasty as a Primary or Revision Patellar Stabilizing Procedure. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117s00388

[13] Trochleoplasty procedures show complication rates similar to other patellar-stabilizing procedures. Knee Surgery, Sports Traumatology, Arthroscopy. 2017. DOI: 10.1007/s00167-017-4766-5

[15] Editorial Commentary: Trochleoplasty: Is It Really That Fearsome and Dangerous a Technique?. Arthroscopy. 2020. DOI: 10.1016/j.arthro.2020.05.050

[16] Isolated Medial Patellofemoral Ligament Reconstruction Results in Lower Failure and Complication Rates Than Isolated Trochleoplasty and Tibial Tubercle Osteotomy: A Systematic Review. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.05.019

[17] Current concepts on trochleoplasty procedures for the surgical treatment of trochlear dysplasia. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3013-6

[18] Trochlear Shape and Patient-Reported Outcomes After Arthroscopic Deepening Trochleoplasty and Medial Patellofemoral Ligament Reconstruction: A Retrospective Cohort Study Including MRI Assessments of the Trochlear Groove. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671231171378

[19] Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocations With Increased Femoral Anteversion and an Absent/Mild J-sign. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465261437776

[21] Conservative versus tailored surgical treatment in patients with first time lateral patella dislocation: a randomized-controlled trial. Journal of Orthopaedic Surgery and Research. 2021. DOI: 10.1186/s13018-021-02513-3

[22] Acceptable outcomes for isolated medial patellofemoral ligament reconstruction despite using higher thresholds for patella alta and regardless the value of tibial tubercle-trochlear groove distance and the degree of trochlear dysplasia—An international multicenter study. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.101028

[23] Evaluating the Outcomes of Trochleoplasty in the Treatment of Patellofemoral Instability in the Adolescent and Young Adult Knee With Severe Trochlear Dysplasia: A Minimum 2-Year Follow-up. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251321499

[24] Trochleoplasty: Indications in patellar dislocation with high-grade dysplasia. Surgical technique. Orthopaedics & Traumatology: Surgery & Research. 2022. DOI: 10.1016/j.otsr.2021.103160

[25] Patients who undergo tibial tubercle anteromedialization with medial patellofemoral ligament reconstruction demonstrate similar rates of return to sport compared to isolated MPFL reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2024. DOI: 10.1002/ksa.12051

[26] Grooveplasty Compared With Trochleoplasty for the Treatment of Trochlear Dysplasia in the Setting of Patellar Instability. Arthroscopy, Sports Medicine, and Rehabilitation. 2022. DOI: 10.1016/j.asmr.2022.11.020

[27] Editorial Commentary : The Entry Point‐Trochlear Groove Angle Measures Lateralization of the Proximal Trochlear Entry Point in Patients With Patellar Instability. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.06.005

[29] Clinical outcomes and predictive factors for failure with MPFL reconstruction combined with tibial tubercle osteotomy and lateral retinacular release for recurrent patellar instability. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04508-x

[30] The Oswestry-Bristol Classification. The Bone & Joint Journal. 2020. DOI: 10.1302/0301-620x.102b1.bjj-2019-0366.r3

[31] Medial Patellofemoral Ligament Reconstruction Using Pedicled Quadriceps Tendon Autograft Yields Similar Clinical and Patient‐Reported Outcomes but Less Donor‐Site Morbidity Compared With Gracilis Tendon Autograft. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.07.006

[32] Trochleoplasty as a Solitary Treatment for Recurrent Patellar Dislocation Results in Good Clinical Outcome in Adolescents. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516652894

[33] The role of the most cranial trochlear orientation in patellar maltracking to better characterise trochlear morphology. Knee Surgery, Sports Traumatology, Arthroscopy. 2024. DOI: 10.1002/ksa.12314

[34] Podium Presentation Title: Grooveplasty vs. Trochleoplasty for Trochlear Dysplasia in the Setting of Patellar Instability. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2023.08.056

[35] Good patient satisfaction with low complications rate after trochleoplasty in patellofemoral instability. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-06954-z

[39] Thin Flap Trochleoplasty With Medial Patellofemoral Ligament Reconstruction for Recurrent Patellofemoral Instability With High-Grade Trochlear Dysplasia: A Series of 63 Consecutive Cases. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465251314882

[41] C‐Arm Guidance During Thin Flap Arthroscopic Trochleoplasty for Chronic Patellar Instability. Arthroscopy Techniques. 2023. DOI: 10.1016/j.eats.2023.04.030

[42] Very low dislocation rate and good clinical outcome after Bereiter trochleoplasty and additional procedures following the Copenhagen patella–femoral instability algorithm: One‐ and two‐years outcomes from a consecutive cohort of 368 cases. Knee Surgery, Sports Traumatology, Arthroscopy. 2025. DOI: 10.1002/ksa.12663

[43] Deepening Trochleoplasty With a Thick Osteochondral Flap for Patellar Instability. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515597679

[45] Trochleoplasty Is Associated With High Rates of Patellofemoral Arthritis: A Systematic Review. Arthroscopy, Sports Medicine, and Rehabilitation. 2026. DOI: 10.1002/ars2.70021

[46] Abnormal patellar loading may lead to femoral trochlear dysplasia: an experimental study of patellar hypermobility and patellar dislocation in growing rats. Journal of Orthopaedic Surgery and Research. 2023. DOI: 10.1186/s13018-023-03500-6

[47] Trochleoplasty with a flexible osteochondral flap. The Bone & Joint Journal. 2017. DOI: 10.1302/0301-620x.99b3.37884

[48] Patellofemoral osteoarthritis after Insall's proximal realignment for recurrent patellar dislocation. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2485-0

[50] Trochleoplasty is a Viable Option for Patellar Instability in Patients with Severe Trochlear Dysplasia: Early Outcomes Analysis of the U.S. Experience. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117s00389

[51] Management of the first episode of traumatic patellar dislocation: an international survey. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07273-z

[52] Classification of trochlear dysplasia as predictor of clinical outcome after trochleoplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1410-7

[53] Deepening trochleoplasty and medial patellofemoral ligament reconstruction normalize patellotrochlear congruence in severe trochlear dysplasia. The Bone & Joint Journal. 2019. DOI: 10.1302/0301-620x.101b3.bjj-2018-0795.r2

[54] Cartilage viability after trochleoplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0148-0

[55] Aaos Comprehensive Orthopaedic Review 3. Anatomy and Biomechanics of the Knee > I. Anatomy.

[58] Campbell S Operative Orthopaedics 4 Volume Set. EXTRAARTICULAR LIGAMENTOUS STRUCTURES.

[69] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > II. Surgical Anatomy of the Knee.

[73] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > I. Radiographic Evaluation.

[81] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 11 KNEE ARTHRITIS ASSESSMENT.

[98] Functional deficits and significant patellofemoral chondral deterioration two years after trochleoplasty and medial patellofemoral ligament reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2025. DOI: 10.1002/ksa.70043

[108] Recession wedge trochleoplasty as an additional procedure in the surgical treatment of patellar instability with major trochlear dysplasia: Early results. Orthopaedics & Traumatology: Surgery & Research. 2011. DOI: 10.1016/j.otsr.2011.07.013

[109] Sulcus deepening trochleoplasty for patellofemoral instability: A series of 34 cases after 15 years postoperative follow-up. Orthopaedics & Traumatology: Surgery & Research. 2015. DOI: 10.1016/j.otsr.2015.01.017

[119] Cadaveric study on static medial patellar stabilizers: the dynamizing role of the vastus medialis obliquus on medial patellofemoral ligament. Knee Surgery, Sports Traumatology, Arthroscopy. 2005. DOI: 10.1007/s00167-005-0631-z

[131] Morphological Improvement of the Epiphyseal Plate and Trochlea After Surgical Correction in Skeletally Immature Patients With Patellar Dislocation and Trochlear Dysplasia. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465241301775

[134] Trochlear Dysplasia Is Associated With Increased Sagittal Tibial Tubercle Trochlear‐Groove Distance in Patients With Patellar Instability. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.05.023

[136] Sulcus-deepening trochleoplasty and medial patellofemoral ligament reconstruction provide good clinical outcomes in addressing patellar instability at mid-term follow-up: A retrospective case series. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.100387

[137] The Anterior-posterior Distance Between the Tibial Tuberosity and Trochlear Groove. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117s00383

[141] A Laterally Positioned Concave Trochlear Groove Prevents Patellar Dislocation. Clinical Orthopaedics & Related Research. 2006. DOI: 10.1097/01.blo.0000203478.27044.9a

[142] Trochleoplasty Versus Nontrochleoplasty Procedures in Treating Patellar Instability Caused by Severe Trochlear Dysplasia. Arthroscopy. 2014. DOI: 10.1016/j.arthro.2014.01.011

[147] A stand-alone lateral condyle-elevating trochlear osteotomy leads to high residual instability but no excessive increase in patellofemoral osteoarthritis at 12-year follow-up. Knee Surgery, Sports Traumatology, Arthroscopy. 2017. DOI: 10.1007/s00167-017-4602-y

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