Patella (Kneecap) Fractures

Patient information — Dr Christopher Spelman, Orthopaedic Surgeon

Overview

The patella (kneecap) is the bone at the front of the knee, embedded in the tendon that straightens the knee. It acts as a lever that makes the quadriceps muscle more efficient. A patella fracture usually results from a direct blow to the front of the knee (such as a fall or a dashboard injury), or occasionally from a sudden violent contraction of the quadriceps. The key question is whether you can still straighten the knee – that is, whether the extensor mechanism is intact.

Assessment

Examination checks whether you can straighten the knee and hold it straight (a straight-leg raise). X-rays show the fracture pattern and how far the fragments have separated. A fracture is considered displaced if the fragments are separated by more than a few millimetres or if there is a step in the joint surface.

Non-operative treatment

Undisplaced fractures where you can still straighten the knee (the extensor mechanism is intact and there is minimal separation and no significant step in the joint surface) can be treated without surgery, in a brace or cast in extension, with a graduated return of movement over several weeks.

Surgical treatment

Displaced fractures, or any fracture where you cannot straighten the knee, are treated surgically to restore the joint surface and repair the extensor mechanism. The fragments are held together, commonly with a “tension band” construct using wires or screws, so that you can regain movement. Very fragmented fractures, or a lower fragment that cannot be reconstructed, may require other techniques.

Recovery

After surgery the knee is protected in a brace, with a carefully graduated programme to regain bending while protecting the repair, followed by strengthening. Restoring full straightening and quadriceps strength is the goal.

Complications

Patella fractures unite reliably, but complications are relatively common because the hardware sits directly under the skin and the bone is loaded every time the knee bends:

●      Symptomatic hardware – prominent or irritating wires/screws are the commonest problem, and removal of the metalwork is one of the most frequent reasons for a second operation.

●      Anterior knee pain and stiffness.

●      Loss of fixation or separation of the fragments, occasionally needing revision.

●      Non-union (uncommon) and post-traumatic arthritis of the joint surface over the longer term.

●      The general risks of surgery – infection and blood clots.

Summary

A kneecap fracture is treated according to whether you can still straighten the knee. Undisplaced fractures with an intact extensor mechanism can be braced, while displaced fractures need surgery to restore movement and knee function. Hardware irritation is common and metalwork is often removed later. Dr Spelman will explain the pattern of your fracture and the recommended treatment.