Measurement Snapshot
ReferenceTraditional reference: 135 degrees
Common Adult RangeCommon adult active range: 130 to 140 degrees
Primary MusclesHamstrings, gastrocnemius, sartorius
Knee flexion ROM is commonly followed after ACL reconstruction, meniscus repair, total knee arthroplasty, and mobility-focused rehabilitation. Interpret change alongside swelling, pain, strength, and surgical precautions.
Standardized Setup
- Patient Position
- Place the patient supine and allow the hip to flex enough that knee bending is not blocked by thigh-abdomen contact too early.
- Stabilization
- Stabilize the femur and pelvis to prevent hip rotation, pelvic lift, or lower-limb abduction during the test.
- Landmarks
- Use the lateral femoral epicondyle as the axis, the greater trochanter as the proximal reference, and the lateral malleolus as the distal reference.
Step-by-Step Protocol
- Calibrate full knee extension as the starting angle when clinically appropriate.
- Flex the knee through the available sagittal-plane range.
- Keep the shin aligned and prevent the hip from rolling outward.
- Record the maximum angle and document supine, prone, active, or passive status.
Common Measurement Errors
- Allowing hip rotation to add apparent knee flexion.
- Changing the pelvis position between repeated measurements.
- Comparing active and passive values without labeling them separately.
Cobb Angle Pro Workflow
- Choose Knee Flexion and place the device along the lateral shin.
- Zero the baseline with the knee at the selected start position.
- Capture the endpoint and save the test position so future comparisons use the same setup.
References
- Petersson LE, Nilsson H. Reliability of knee joint range of motion measurements. Physiotherapy Res Int. 2002;7(2):87-95.
- Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. 5th ed. F.A. Davis Company; 2016.