Patella Alta: Causes, Pathophysiology, Diagnosis, and Management

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 Patella Alta: Causes, Pathophysiology, Diagnosis, and Management

Case Reference: 62-year-old male, presenting with acute left knee pain following a fall with the knee flexed, unable to walk, diagnosed with Patella Alta (Figures 1–3).

Introduction

Patella alta, literally meaning high-riding patella, is an orthopedic condition characterized by an abnormally superior position of the patella concerning the femoral trochlea. This condition often results from traumatic injury to the patellar tendon, congenital anomalies, or chronic biomechanical stress. Although patella alta can be asymptomatic in some individuals, it may predispose patients to anterior knee pain, instability, and patellofemoral joint disorders.

The presented case exemplifies the classic acute presentation of patella alta following a traumatic patellar tendon rupture. Early recognition is crucial because delayed treatment can lead to chronic functional impairment.

Cause and Etiology

The most common etiology of patella alta in adults is patellar tendon rupture, often secondary to:

  • Direct trauma: e.g., fall on a flexed knee (as in the present case).

  • Indirect trauma: sudden, forceful contraction of the quadriceps muscle against resistance.

  • Degenerative changes: tendinopathy, microtears from repetitive stress.

  • Systemic diseases: rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus, and chronic kidney disease.

  • Steroid injections: long-term corticosteroid exposure may weaken tendon integrity.

In pediatric populations, congenital forms exist and may be associated with connective tissue disorders such as Ehlers–Danlos syndrome.

Pathophysiology

The patellar tendon connects the inferior pole of the patella to the tibial tuberosity. Rupture of this tendon allows the quadriceps to retract the patella proximally, resulting in an abnormally high position. This disrupts the extensor mechanism, preventing active knee extension. The biomechanical consequences include:

  • Increased patellofemoral contact forces during flexion.

  • Altered tracking of the patella.

  • Potential for early-onset patellofemoral osteoarthritis.

Epidemiology

  • Incidence: Rare; patellar tendon ruptures account for <1% of all tendon injuries.

  • Age: Typically affects active adults aged 30–50; traumatic cases in elderly patients are often linked to degenerative tendon changes.

  • Sex: More common in males due to higher exposure to high-impact sports and physical labor.

  • Risk factors: Pre-existing tendinopathy, chronic diseases affecting collagen metabolism, and previous knee surgery.

Clinical Presentation

  • Acute pain: Sudden, severe anterior knee pain following injury.

  • Functional loss: Inability to extend the knee or bear weight.

  • Physical examination:

    • Swelling and effusion (Figure 1).

    • Palpable gap below the patella.

    • Superiorly displaced patella (patella alta).

    • Positive “Lag” sign: inability to perform straight leg raise.

Imaging Features

  1. Plain Radiography

    • Lateral view: Demonstrates high-riding patella (Figure 2).

    • Insall–Salvati ratio: A ratio of>1.2 suggests patella alta.

    • Absence of fracture.

  2. Magnetic Resonance Imaging (MRI)

    • T2-weighted images: Show discontinuity of patellar tendon fibers, surrounding edema, and possible hemorrhage (Figure 3).

    • MRI also helps differentiate partial vs complete tears and identify associated injuries.

Treatment

Acute Management

  • Complete ruptures: Surgical repair is the gold standard.

    • Tendon reattachment to the patella or tibial tuberosity using suture anchors or transosseous tunnels.

  • Partial ruptures: May be treated conservatively with immobilization followed by rehabilitation.

Rehabilitation

  • Immobilization for 4–6 weeks in extension.

  • Gradual passive and active range-of-motion exercises.

  • Progressive strengthening of quadriceps and hamstrings.

Surgical Prognosis

  • Early surgery (<2 weeks) yields better outcomes.

  • Delayed repairs may require tendon graft augmentation.

Prognosis

Most patients regain functional mobility, though mild range-of-motion limitations can persist, as in the presented case. Prognostic factors include:

  • Age

  • Extent of rupture

  • Timeliness of surgical repair

  • Adherence to rehabilitation protocols

Case Summary

A 62-year-old man presented with acute inability to walk after a fall with the knee flexed. Clinical examination revealed swelling and a high-riding patella (Figure 1). Lateral knee X-ray confirmed patella alta (Figure 2), and T2-weighted MRI demonstrated patellar tendon discontinuity (Figure 3). The patient underwent surgical repair and completed physiotherapy. At 6 months, he had minimal residual limitation in flexion/extension but was able to ambulate independently.

Figures

Figure 1: Clinical photograph showing swelling and superior displacement of the left patella.

Figure 2: Lateral knee radiograph illustrating high-riding patella (Insall–Salvati ratio >1.2).

Figure 3: T2-weighted MRI of the left knee revealing patellar tendon discontinuity (asterisk).

Quiz

Q1. Which imaging modality is most sensitive for detecting patellar tendon rupture?

Q2. What is the Insall–Salvati ratio threshold for diagnosing patella alta?

Q3. Which surgical principle is critical for optimal recovery in complete patellar tendon rupture?

Answer & Explanation

1. Answer: MRI. Explanation: MRI provides detailed visualization of soft tissue structures, allowing for the confirmation of tendon discontinuity and the assessment of associated injuries.

2. Answer: >1.2,  Explanation: The ratio compares patellar tendon length to patella length; values above 1.2 indicate an abnormally high patella.

3.  Answer: Early repair within 2 weeks of injury. Explanation: Early intervention reduces tendon retraction, scar formation, and postoperative stiffness, improving functional outcomes.

References

[1] A. Kannus and P. Järvinen, "Tendon injuries of the knee," Clin. Orthop. Relat. Res., vol. 236, pp. 110–119, 1988.
[2] M. Insall and E. Salvati, "Patella position in the normal knee joint," Radiology, vol. 101, no. 1, pp. 101–104, 1971.
[3] S. Siwek and D. Rao, "Ruptures of the extensor mechanism of the knee joint," J. Bone Joint Surg. Am., vol. 63, no. 6, pp. 932–937, 1981.
[4] C. Matava, "Patellar tendon ruptures," J. Am. Acad. Orthop. Surg., vol. 4, no. 6, pp. 287–296, 1996.
[5] J. Clayton and D. Court-Brown, "The epidemiology of musculoskeletal tendinous and ligamentous injuries," Injury, vol. 39, no. 12, pp. 1338–1344, 2008.
[6] J. Grelsamer and R. Meadows, "The modified Insall–Salvati ratio for assessment of patellar height," Clin. Orthop. Relat. Res., vol. 282, pp. 170–176, 1992.
[7] R. Ilan et al., "Acute patellar tendon rupture: A clinical and imaging review," AJR Am. J. Roentgenol., vol. 189, no. 3, pp. 721–729, 2007.

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