Joints and Joint Function Defined
A joint is defined as the juncture where bones and muscles come together, facilitating movement and stability. Contraction of muscles crossing the joint can stabilize it or cause it to move. Normal joint function is defined as a joint’s ability to move throughout its range of motion and bear weight.
Your healthcare provider or physical therapist can examine the structure and function of the bones, muscles, ligaments, tendons, nerves, and blood supply of a joint.
The physical examination of your joint involves an assessment of how far it can flex, extend, and rotate. Your ability to bear weight on your joint and resist pressure opposing the action of the joint are other aspects of joint function.
Assessing Joint Function
When you go to the practitioner with a complaint about a bone, muscle, or joint, your healthcare provider will perform a musculoskeletal examination that includes assessing your joint function.
Joint function can be affected by injury or inflammation, and your practitioner will compare each joint’s appearance to the opposite corresponding joint—looking for signs like redness, swelling, or bruising.
Your healthcare provider will ask you to actively move your joint through its usual range of motion —flexing, extending, and rotating. Your practitioner will also passively move your joint.
Restrictions in your strength or range of motion during passive or active movement signal joint problems.
Pain is a sign of joint injury or disease. Another sign— crepitus (crackling)—suggests degeneration of the joint.
Example of Shoulder Joint Function Tests
The range of motion tests for the shoulder include:
Abduction: The ability to lift your arm away from your bodyFlexion: The ability to extend your arm over your headAdduction: Moving your arm to your sidesInternal rotation and external rotation: Twisting your arm forward and back from your shoulder
Other tests include Neer’s Test and Hawkin’s test for impingement and the Empty Can and Gerbers Liftoff tests for rotator cuff injuries.
Example of Knee Joint Function Assessment
Your healthcare provider will observe you as you stand in place to see whether your legs are bowed or knock-kneed (varus vs. valgus deformity), which are signs of impaired knee joints. Your practitioner will also examine your knee joint by watching you walk to see if you have a limp.
Your ability to get out of a chair and climb stairs also rely on your knee joint function.
Your healthcare provider will ask you to lie down and will passively bend your knee. Normally, you should be able to passively and actively extend your knee to zero degrees (straighten your leg) and flex it to 140 degrees.
Other tests for knee joint function include the McMurray’s Test and Appley Grind Test for medial meniscus injury, stress tests for the lateral collateral ligament and medial collateral ligament, Lachman’s test for the anterior cruciate ligament, Posterior Drawer Test, and chondromalacia tests.
