Notes · Orthopaedics · 31 October 2026

Avulsion fracture of tibial tuberosity

Definition

• An avulsion fracture of the tibial tuberosity is a separation of a fragment of bone from the anterior proximal tibia where the patellar tendon inserts.
• The fracture occurs when the tensile force generated by the quadriceps‑patellar mechanism exceeds the strength of the growth plate (physis) or the ossified bone in adolescents.

Epidemiology

• Rare injury, accounting for <1 % of all physeal fractures.
• Predominantly affects males (≈ 90 %) aged 12–16 years, coinciding with the adolescent growth spurt.
• Higher incidence in athletes involved in jumping sports (basketball, volleyball, gymnastics).
• Bilateral involvement is uncommon (< 5 % of cases).

Aetiology (Risk Factors)

• Acute high‑impact loading: sudden forceful knee extension during a jump or sprint.
• Chronic repetitive micro‑trauma: overuse of the quadriceps‑patellar unit in growing adolescents weakens the apophyseal cartilage.
• Pre‑existing conditions: Osgood‑Schlatter disease (chronic tibial tubercle apophysitis) predisposes to fracture.
• Nutritional deficiencies: low calcium/vitamin D may impair bone mineralisation.
• Sex hormones: testosterone‑driven rapid growth leads to a relatively weaker physeal plate.

Pathophysiology

1. Physeal anatomy: The tibial tuberosity develops from a secondary ossification centre that fuses to the proximal tibial epiphysis around 14–16 years.
2. Force transmission: During knee extension, the quadriceps contracts, pulling the patellar tendon attached to the tuberosity.
3. Failure point: In adolescents, the physeal cartilage is the weakest link; when the tensile load exceeds its tensile strength, the cartilage ruptures and a bone fragment is pulled away (avulsion).
4. Fracture pattern:
   • Type I (Ogden classification): small fragment, minimal displacement.
   • Type II: larger fragment, displacement ≤ 2 cm, intact posterior cortex.
   • Type III: comminuted fragment, displacement > 2 cm, posterior cortex disrupted.
5. Associated injuries: Rarely, the fracture can extend into the proximal tibial metaphysis or cause a concurrent meniscal tear due to sudden knee flexion.

Clinical Features

• History: Sudden sharp pain over the anterior knee during a jump or sprint; inability to continue activity; audible “pop” may be reported.
• Inspection: Swelling and bruising over the tibial tuberosity; possible palpable gap at the site of avulsion.
• Palpation: Tenderness over the tibial tuberosity; the fragment may be palpable as a mobile bony lump.
• Range of Motion (ROM): Painful knee extension; active knee extension is weak or absent; passive flexion may be preserved.
• Functional test: Inability to perform a straight‑leg raise (SLR) indicates disruption of the extensor mechanism.
• Neurovascular status: Typically intact; assess distal pulses and sensation to rule out compartment syndrome.

Investigations

Management (Current Guideline – 2024 AO/OTA & AAP Recommendations)

General Principles

• Prompt reduction of the extensor mechanism to prevent chronic quadriceps weakness.
• Early mobilisation of the knee after stable fixation to avoid joint stiffness.

Non‑operative (Conservative) Treatment

• Indicated for type I fractures with ≤ 2 mm displacement and intact posterior cortex.
• Immobilisation: Long leg cast or hinged knee brace locked in 0–15° flexion for 4 weeks.
• Weight‑bearing: Non‑weight‑bearing (NWB) for the first 2 weeks, then partial weight‑bearing (PWB) as tolerated.
• Physiotherapy: Initiate passive ROM after 2 weeks; active quadriceps strengthening after cast removal.

Operative Treatment

• Indicated for type II (displacement > 2 mm) and type III fractures, or when the fragment is intra‑articular.
• Surgical approach: Anterior longitudinal incision over the tibial tuberosity.
• Fixation methods:
  • Screw fixation (cannulated cancellous screws) – preferred for larger fragments.
  • Kirschner wire (K‑wire) fixation – used for small fragments or in younger children.
  • Suture anchor technique – adjunct when the fragment is too small for hardware.
• Post‑operative protocol:
  • Immediate immobilisation in a knee brace locked in extension for 2 weeks.
  • NWB for 2 weeks, then PWB with brace unlocked to 30° flexion for another 2 weeks.
  • Full weight‑bearing and brace removal at 6 weeks if radiographs show union.
  • Progressive ROM and strengthening from week 6 onward.

Rehabilitation Highlights (2024)

• Phase 1 (0–2 weeks): Pain control, edema reduction, isometric quadriceps activation.
• Phase 2 (2–6 weeks): Controlled passive flexion up to 90°, active assisted ROM, gentle patellar mobilisations.
• Phase 3 (6–12 weeks): Full active ROM, closed‑chain strengthening, proprioceptive training.
• Return to sport: Typically 4–6 months after fracture union, after passing functional hop tests and quadriceps strength ≥ 90 % of the contralateral side.

Complications

• Non‑union or delayed union: More common with inadequate fixation or premature weight‑bearing.
• Malunion: Leads to tibial tuberosity prominence, altered patellar tracking, and extensor lag.
• Compartment syndrome: Rare but life‑threatening; monitor for increasing pain, tense calf, and neurovascular changes.
• Growth disturbance: Physeal injury may cause premature closure, resulting in tibial length discrepancy or angular deformity.
• Patellar tendon rupture: May occur if the fragment is missed and the tendon remains under tension.
• Hardware irritation: Prominent screws or K‑wires may require removal after fracture healing.

High‑Yield Exam Points

• Age & gender: Typical adolescent male (12‑16 years).
• Mechanism: Sudden forceful knee extension during jumping.
• Key clinical sign: Inability to perform a straight‑leg raise (extensor mechanism disruption).
• Radiographic classification: Ogden type I (non‑displaced), type II (displaced ≤ 2 cm), type III (comminuted > 2 cm).
• Management algorithm: Non‑operative for type I; operative fixation for type II/III or > 2 mm displacement.
• Post‑operative immobilisation: Brace locked in extension for 2 weeks, then gradual flexion.
• Complication to watch: Compartment syndrome – check for pain out of proportion and tense anterior compartment.
• Rehabilitation goal: Full ROM and ≥ 90 % quadriceps strength before return to sport.

Practice questions

1. A 14‑year‑old male basketball player presents with acute anterior knee pain after a jump. Radiograph shows a 3 mm displaced fragment of the tibial tuberosity with an intact posterior cortex. The best initial management is:
Answer: B — closed reduction and casting for 4 weeks (type II fracture with minimal displacement managed conservatively).

2. Which of the following is the most common complication specific to tibial tuberosity avulsion fractures in adolescents?
A. Deep vein thrombosis
B. Growth plate arrest
C. Patellar dislocation
D. Osteoarthritis
Answer: B — growth plate arrest can occur due to physeal injury.

3. According to the 2024 AO/OTA guidelines, the preferred fixation method for a displaced tibial tuberosity fragment larger than 1 cm is:
A. Kirschner wire fixation
B. Cannulated cancellous screw fixation
C. External fixation
D. Plate fixation
Answer: B — cannulated cancellous screw fixation provides stable compression for larger fragments.

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