Tibial Tubercle Avulsion 

Updated: May 27, 2020
Author: Janos P Ertl, MD; Chief Editor: Thomas M DeBerardino, MD 


Practice Essentials

A tibial tubercle avulsion fracture is usually an injury to the knee occurring in adolescence, during the transitional phase of physeal closure just prior to completion of growth.[1, 2]  This fracture most often is an isolated injury related to pushoff or landing while jumping as the quadriceps eccentrically contracts to support the individual's weight.

The fracture tracks through the proximal tibial epiphysis and may extend into the anterior portion of the knee joint. The proximal tibial physis closes from posterior to anterior, and the fracture pattern is dependent on the amount of physeal closure present at the time of injury. Some authors consider this injury to be a variant of a Salter-Harris III fracture pattern. Open reduction with internal fixation (ORIF) is recommended, in that reduction is difficult to maintain against the pull of the quadriceps muscle.

An extended classification system was developed that includes types I, II, III, IV, and V. Types I, II, and III were described by Watson-Jones; these may be further divided into A, B, and C subtypes, with A indicating displacement, B indicating comminution, and C (added by Frankl) indicating associated patellar ligament avulsions. For classification of more extensive injury, type IV was introduced by Ryu and type V by Mckoy.[3]

For all fracture types, ice therapy, splint immobilization, and elevation should be initiated to avoid significant swelling. Type I fractures generally can be treated with cast immobilization; often, percutaneous or open reduction can be performed to maintain motion within the knee. Types IB, II, and III tibial tubercle fractures require ORIF. In type III injuries, exploration of the knee joint is necessary to address intra-articular comminution and possible meniscal pathology.

The difficulty with this fracture is in maintaining a satisfactory reduction against the proximal pull of the quadriceps muscle. The patient usually is very close to the end of growth, and fixation of the fragment should not affect remaining growth. In the rare instance in which this fracture occurs in a younger individual, suturing of the periosteum and retinaculum and temporary smooth Kirschner wire (K-wire) fixation may be performed.


The proximal tibia physis progressively closes from posterior to anterior. The tibial tubercle is vulnerable to injury during the transitional phase of closure.

The tibial tubercle physis is in continuity with the tibial plateau. The physis progressively fuses from posterior to anterior, making it most vulnerable to avulsion in adolescents aged 13-16 years.


The mechanism of injury usually is an indirect force caused by sudden contraction of the quadriceps muscle. During sudden acceleration and deceleration forces, the quadriceps mechanism forcefully contracts against the patellar tendon insertion. When the force is greater than the strength of the tibial tubercle physis, a fracture is created, leading to avulsion of the tibial tubercle. Additional predisposing factors include patella baja, tight hamstrings, preexisting Osgood-Schlatter disease, and disorders involving physeal abnormalities.[4]


Tibial tubercle avulsion fractures are commonly seen in athletic males (frequently basketball players) aged 14-16 years.[5] These fractures account for fewer than 1% of physeal fractures. Their incidence in children, though still low, appears to be increasing, possibly because of greater participation in high-level athletics.[6]  Bilateral tibial tubercle avulsion fractures may occur but are quite rare.[7]


With appropriate surgical treatment and postoperative therapy, a complete recovery without residual symptoms is expected. A return to sports may be expected once the strength of the affected lower extremity reaches 90% of that of the unaffected extremity (usually 4-6 months after injury).

In a systematic review of the English-language literature on pediatric tibial tubercle fractures from 1970 to 2013, Pretell-Mazzini et al examined treatment outcomes (functional and radiologic) and complications.[8]  Clinical outcomes were evaluated on the basis of qualitative assessment, return to preinjury activity, and range of motion (ROM) in the knee. Fracture healing, associated injuries, compartment syndrome, and complications were assessed as well.

In this study, 98% of surgical cases were treated with ORIF.[8] ​ Fracture consolidation was accomplished in 99.4% of cases, and 98% of patients, regardless of fracture type, were able to return to preinjury activity and regain knee ROM. The overall complication rate was 28.3%, with the most frequent complication being removal of an implant because of bursitis (55.8%), followed by tenderness/prominence (17.9%) and refracture (6.3%). The incidence of compartment syndrome was 3.57%. The authors noted the need for longer follow-up to determine long-term outcomes.



Physical Examination

The physical examination reveals swelling and tenderness over the anterior tibia. A palpable bone fragment and hemarthrosis may be present. With severe displacement, a high-riding patella and loss of active knee extension are present. In the presence of extensive bleeding due to displacement, tension in compartments of the lower extremity may be appreciated.


Watson-Jones classified these fractures into three types on the basis of size and amount of displacement,[9]  as follows (see the image below):

  • In type I injures, a small fragment is minimally displaced proximally
  • In type II injuries, the secondary center of ossification has coalesced with the proximal tibial epiphysis, with the fracture occurring at this junction; an intact superior contact is maintained between the avulsed portion of the tibial tubercle and the remaining portion of the tibial epiphysis, the articular surface remains intact
  • In type III injuries, the fracture extends through the articular surface; comminution and meniscal disruption may be present
Diagrammatic view of tibial tubercle avulsion clas Diagrammatic view of tibial tubercle avulsion classification types I, II, and III.

Ogden further subdivided the Watson-Jones classifications into A and B categories to account for the degree of displacement (A) and comminution (B).[10, 11]  In current usage, types I, II, and III can be divided into A, B, and C subtypes, with A indicating displacement, B indicating comminution, and C indicating associated patellar ligament avulsions.

To address more extensive injures, the original classification was expanded to include two more main types, as follows (see the image below)[3] :

  • Type IV injury is a fracture that involves the complete tibial epiphysis
  • Type V injury is an avulsion fracture that has complete epiphyseal involvement with interarticular involvement, or a combination of types IIIA and IV
Extended classification system for tibial tubercle Extended classification system for tibial tubercle avulsion injury.


Imaging Studies

Standard radiographs, including anteroposterior (AP), lateral, oblique, and 15º cephalad views of the knee, are recommended. (See the images below.) Tibial tubercle avulsion injuries usually are isolated, and any additional injuries require further evaluation as indicated for that injury.

Anteroposterior view of a type II tibial tubercle Anteroposterior view of a type II tibial tubercle avulsion. The injury could be missed if a lateral view is not obtained.
Type III tibial tubercle avulsion. Note intra-arti Type III tibial tubercle avulsion. Note intra-articular fracture extension and anterior elevation.


Approach Considerations

Type I fractures are minimally displaced. Even though such fractures may not be displaced, it is difficult to maintain this reduction against the pull of the quadriceps muscle. Type I fractures generally can be treated with cast immobilization. However, close observation in the first 2 weeks is necessary. Often, percutaneous or open reduction can be performed to maintain motion within the knee.

Type II lesions maintain an intact superior contact between the avulsed portion of the tibial tubercle and the remaining portion of the tibial epiphysis. The articular surface of the knee is not disrupted. In type III injuries, the fracture extends through the articular surface of the knee with occasional meniscal disruption.

Type II and III injuries require stabilization of the extensor mechanism through an open technique to replace the fragment and to remove any interposed periosteum. Displaced types II and III avulsion fractures require operative fixation because of loss of the extensor mechanism length, tension, and continuity.[12, 13, 14]  In type III injuries, exploration of the knee joint is necessary to address intra-articular comminution and possible meniscal pathology that may necessitate meniscal  repair.

Surgical Therapy

For all fracture types, ice therapy, splint immobilization, and elevation should be initiated to avoid significant swelling.[15, 16, 17, 18]

Types IB, II, and III tibial tubercle fractures require open reduction with internal fixation (ORIF). An anterior approach to the knee is followed over the proximal tibia. Fixation is best accomplished with one or two screws through the tibial tubercle into the proximal tibia. C-arm control is recommended to avoid overpenetration of the posterior tibial cortex.

Growth arrest is uncommon, in that this fracture usually occurs at the end of physeal closure. Should significant growth remain, smooth Kirschner wires (K-wires) may be used temporarily to allow continued growth and avoid the possibility of recurvatum (hyperextension). In younger patients, the periosteum and retinaculum may be sutured. The screws should be placed at a right angle to the avulsed fragment, proximally and posteriorly, not inclined distally, to avoid a tendency to pull out.

In type III fractures, comminution and meniscal disruption may be present. An anterior medial arthrotomy is recommended for visualization and exploration. Anatomic reduction should be the goal. Temporary fixation with K-wires may be applied and radiographically evaluated before definitive fixation. Meniscal tears should be repaired, and tibial plateau articular continuity should be reestablished. (See the image below.)

Intraoperative view after open reduction and inter Intraoperative view after open reduction and internal fixation of a type III tibial tubercle avulsion.

An advanced approach to evaluation and treatment is arthroscopic-assisted reduction and internal fixation. The tibial plateau can be visualized, fragments repositioned, and meniscal pathology addressed. Cross-training in both arthroscopic techniques and fracture treatment is necessary.

Should a compartment syndrome be identified, preparation is made for release of all the affected compartments. Because of the large vascular bone surface involved, this may be found in type III patterns.

A study of 12 children with acute tibial tubercle avulsion was undertaken by Pesl and Havranek to determine optimal treatment for various types of the injury.[12] They found that in patients with displaced extra-articular injury (types IB and IIA), ORIF was required. Closed reduction and internal fixation was found to be sufficient in intra-articular fractures (types IIIA and IIIB), except for one case.

Abalo et al found that closed reduction and cast immobilization were acceptable therapy for minimally displaced tibial tubercle fractures and that ORIF was favored for displaced fractures.[13]

Zrig et al treated nondisplaced tibial tubercle fractures conservatively, with immobilization for 6 weeks, and displaced fractures with internal fixation with plaster for 6 weeks and noted satisfactory results in all cases, consisting of functional recovery, resumption of sports activities to previous levels, and an absence of recurvatum.[14]

A small study by Checa Betegón et al (N = 10) suggested that some pediatric tibial tubercle avulsion fractures generally regarded as requiring surgery may be manageable by nonsurgical means.[19]  Of the 11 acute avulsions (one type I, three type II, four type III, and three IV), five were treated conservatively (including all three type IV), and only six were treated surgically. Results were satisfactory in all cases, with a 100% percentage of sport reincorporation in less than 25 weeks. The only reported complication, intolerance of material, did not require additional surgery.

A study comparing the outcomes of unicortical and bicortical fixation in pediatric tibial tubercle avulsion fractures found no significant differences, with all patients showing full healing and return to activities with very low complication rates.[20]  These results suggested that unicortical fixation suffices for these fractures.

Procedural details

Surgical preparation should include a preoperative planning for the following:

  • Anterior surgical approach
  • Removal of interposed soft tissue (periosteum)
  • Evaluation for intra-articular extension, comminution, or meniscal tear, usually type III injuries
  • Reduction of fragment with bone reduction forceps
  • Evaluation of reduction under fluoroscopic control
  • Placement of one or two interfragmentary compression screws; possible washers, cannulated or noncannulated
  • Evaluation of fixation with fluoroscopy
  • Repair of periosteum
  • Evaluation of fixation stability
  • Wound closure
  • Placement of range-of-motion (ROM) brace

In all open reductions, check for interposed periosteum, remove from the fracture site, and maintain the periosteal attachment for later repair. In type III fractures, a medial peripatellar arthrotomy may be necessary to evaluate the articular surface for comminution, as well as for possible meniscal tear.

Postoperative Care

If the fixation is believed to be stable, ROM therapy is initiated. Consultation with a physical therapist (PT) is requested for crutch-assisted touchdown weightbearing (TDWB) ambulation. Heel sliding under PT assistance or continuous passive motion (CPM) is initiated.

CPM is started from 0º to 45° at 2 cycles/min. It is then increased incrementally over a 1- to 2-week period or as the patient tolerates. TDWB is continued for a minimum of 5-6 weeks, at which time progressive full weightbearing may be resumed. Lower-extremity strengthening and hamstring stretching exercises also are started at this time.


Complications of treatment of tibial tubercle avulsion fracture include genu recurvatum (hyperextension) due to premature physeal closure of the anterior physis. However, this complication is rare because the fracture usually occurs in the transitional physis, near the end of closure and growth.

Residual knee stiffness may occur secondary to prolonged immobilization and arthrofibrosis.

Patella alta may occur if the reduction is not anatomic or if fixation is not stable enough, leading to proximal migration of the tubercle fragment.[21, 22]

An episode of a type III injury in an athlete that led to compartment syndrome is described: The patient was playing basketball and sustained an acute type III injury. The patient was seen in an emergency department, placed on crutches, and told to follow up at his home of record. No immobilization was given. The patient was placed on a commercial airplane with his leg maintained in a dependent position. Upon arrival, the patient exhibited a full-blown compartment syndrome, necessitating a four-compartment fasciotomy. Arthroscopy and internal fixation of the fracture were performed.

Long-Term Monitoring

The patient is discharged from the hospital when pain is manageable on an outpatient basis. Follow-up evaluations are performed at 10-14 days, 4 weeks, 2 months, 3 months, and 6 months, with anteroposterior (AP) and lateral radiographs obtained until the fracture has healed. Additional visits may be required, depending on patient progress. The brace is removed after 5-6 weeks. Physical therapy is continued on an outpatient basis as outlined above.