Proprioception testing

Proprioception is the sense of your body's position, movement, and force without having to look. It arises from the combined information sent by the muscle spindles within muscles, Golgi tendon organs in tendons, and receptors around joints. It is why you can touch your nose with your eyes closed or walk down stairs in a dark room.

But this sense is not a single ability. Muscle spindles signaling changes in length, Golgi tendon organs signaling the amount of force, and detecting the onset of very slow movement rely on different signals. Testing is therefore divided into three types, depending on what is being assessed.

This is the most widely used method. Here is how it works.

1. The person sits or lies down with their eyes covered or closed. 2. The examiner moves the joint to a specific angle and holds it there for a few seconds. The person memorizes that angle. 3. The joint is returned to its starting position. 4. The person tries to reproduce the same angle, and the difference between the target angle and the reproduced angle is measured.

There are two methods: active reproduction, in which the person moves the joint themselves to find the angle again, and passive reproduction, in which the examiner moves it slowly and the person asks them to stop when it feels like “this is the spot.” Active reproduction tends to produce smaller errors because the muscles are actively working, while passive reproduction is described as reflecting the role of joint receptors more closely.

Angles are measured using a goniometer, inclinometer, electronic angle sensor, or strength-testing equipment. A smaller error means the person senses that angle more accurately.

There is one point to keep in mind. Reproduction error reflects both the ability to sense the angle and the motor performance needed to move back to it. It is therefore more accurate to interpret the result as a combined sensory and movement ability.

This test involves remembering and reproducing the amount of force, rather than an angle.

1. While watching a screen, the person produces a target force once (for example, 30% of maximum strength), taking note of how that force feels. 2. With the screen turned off and their eyes closed, the person tries to produce the same amount of force again. 3. The difference between the target force and the force actually produced is measured.

Information about the amount of force is described as relying mainly on the Golgi tendon organs, which sense tension in tendons, and information from the brain's motor commands. Someone who accurately matches a position may be less accurate at matching force, or vice versa, so there is value in testing the two separately.

With the person completely relaxed, a device begins moving the joint very slowly (often at 1 degree per second or less). The person presses a button as soon as they feel that “it seems to be moving.” The angle through which the joint has moved between the start of movement and its detection is the detection threshold. A smaller angle means the person can detect even very small movements.

Of the three tests, this comes closest to measuring “pure sensation,” because no reproduction movement is involved. However, the testing conditions must be carefully controlled. If pressure against the skin or noise from the equipment provides a cue, the person may be detecting that cue rather than sensing the joint. Devices such as pneumatic cuffs and headphones are therefore used to block other cues.

• Rehabilitation after a joint injury — Changes in joint position sense have been reported after ankle sprains and knee anterior cruciate ligament injuries, so these tests are used for comparison during rehabilitation.
• Comparison before and after proprioceptive exercise — They are used to examine changes before and after proprioceptive training or balance training.
• Sports settings — They are used to assess an athlete's joint sensation or compare joints on the two sides.
• Research — They are used to study changes in sensation associated with age, fatigue, brace use, and joint condition.

• Each test assesses something different. The same person may have a small position-sense error but a high detection threshold. This is not because the tests are poorly designed, but because they measure different components of sensation. Rather than generalizing one test result to a person's overall proprioceptive ability, it is better to interpret it alongside the type of test used.
• Values vary with the testing conditions. The starting angle, movement speed, how fully vision and hearing are blocked, and sitting posture can all affect the numbers, making direct comparisons between different studies difficult. Repeated measurements of the same person under the same conditions are the most dependable. For more details, see Inter-rater reliability and Test accuracy and measurement terminology.
• Repetition can help people get the hang of the test. Repeating the same test can reduce errors as the person becomes more familiar with it. When scores improve after training, consider whether sensation itself has improved or whether the person has simply become more familiar with the test.
• The relationship between scores and injury is still being studied. Many observations have accumulated showing that proprioceptive measures change after joint injury. However, whether those changes were a cause or a consequence of injury, and whether scores directly predict injury, remain areas of ongoing research.

Standing on one leg with your eyes closed is widely used as a simple way to assess balance. In addition to proprioception, this test involves the vestibular system, vision, sensation from the soles of the feet, and muscle strength. Unlike the three tests above, it does not measure proprioception in isolation; it is more accurately interpreted as an assessment of overall balance ability. For more on balance, see Static balance and Dynamic balance.

Precise testing requires equipment, but there are also simple ways to explore this sense.

• Matching a knee angle — Sit with your eyes closed, slowly raise one leg, and stop when the knee is about halfway straight. Open your eyes to check, then close them again and try to find the same position. You can also compare the two sides.
• Standing on one leg with your eyes closed — Try standing with your eyes closed safely near a wall. Since you could fall, do this somewhere you can put a hand out for support.

These activities are exercises to engage your senses, not tests. Stop immediately if you feel uncomfortable or dizzy.