Can inability to fully extend the knee lead to functional loss?

Inability to Fully Extend the Knee and Functional Loss

Yes, inability to fully extend the knee (extension deficit) leads to significant functional loss in daily activities, mobility, and quality of life.

Impact on Function and Mobility

• A preoperative extension deficit (lack of full extension) is a major risk factor for persistent extension deficit after surgical interventions like anterior cruciate ligament reconstruction 1
• Extension deficit in the knee affects normal gait mechanics, causing increased energy expenditure, slower walking velocity, and abnormal loading patterns that can overload the contralateral limb 2
• Patients with extension deficits demonstrate significant reductions (up to 50%) in peak knee flexion moments during activities like stair climbing, indicating compensatory movement patterns 3
• The inability to fully extend the knee results in greater force of quadriceps contracture, leading to increased energy demands during ambulation 2

Specific Functional Limitations

• Extension deficits impair basic mobility functions including:

  • Walking speed and distance 4
  • Stair climbing and descending ability 3
  • Rising from a seated position 5
  • Balance and stability during standing and movement 5

• Knee osteoarthritis patients with limited extension spend significantly more time sedentary (61% of waking hours), with frequent prolonged sedentary bouts exceeding 30 minutes 4

Clinical Recognition and Exceptions

• The BMJ clinical practice guideline specifically identifies patients who are "objectively unable to fully extend their knee" as a distinct clinical subgroup that may require different management approaches compared to typical degenerative knee disease 1

• This condition represents one of the few exceptions where surgical intervention might be considered beneficial, as noted in the BMJ guideline which states: "the recommendation applies to all or almost all patients with degenerative knee disease. Further, the evidence applies to patients with any severity of mechanical symptoms, with the only possible exception being those who are objectively unable to fully extend their knee (that is, a true locked knee)" 1

Management Considerations

• Physical therapy focusing on regaining extension should be prioritized before considering surgical options 6
• For cases requiring surgery, techniques to address flexion contractures include adequate bone resection, ligament releases, removal of posterior osteophytes, and posterior capsular releases 2
• Post-operative management to maintain extension is critical and may include specialized physical therapy, modified continuous passive motion, contralateral heel lift, and splinting 2

Long-term Consequences

• Residual flexion contractures after knee surgeries have been associated with poorer functional scores and outcomes 2
• Although some flexion contractures may resolve with time after surgery, a substantial percentage will become permanent if not properly addressed 2
• Persistent extension deficits contribute to abnormal biomechanics that can accelerate joint degeneration and functional decline 2, 3

Prevention and Early Intervention

• Early identification and treatment of extension deficits is crucial, as they tend to worsen over time if left untreated 1, 2
• Prehabilitation (pre-operative rehabilitation) may help improve extension and overall outcomes in patients requiring surgical intervention 1
• Strengthening exercises for quadriceps and hamstrings are essential components of rehabilitation programs for patients with extension deficits 7