Range of motion (ROM) refers to the distance and direction a joint can move, involving flexion (bending) and extension (straightening) for the knee. A healthy knee typically moves from zero degrees (full extension) to approximately 135 to 150 degrees of flexion. Maintaining good knee ROM is important because daily activities require specific degrees of movement. For instance, walking requires up to 65 degrees of flexion, climbing stairs demands about 85 degrees, and sitting down requires around 90 degrees.
Understanding Restricted Knee Movement
The knee’s movement can become restricted due to several biological and mechanical factors affecting the joint and surrounding tissues. One common cause is inflammation, occurring in conditions like osteoarthritis or after an acute injury. Swelling within the joint capsule, known as joint effusion, limits the space available for movement. This triggers pain receptors, leading to muscle guarding and stiffness.
Another significant cause of limitation is the formation of scar tissue, or arthrofibrosis, which frequently occurs after surgery or major injury. Scar tissue is composed of collagen fibers laid down in tight strands that lack the elasticity of healthy tissue. This binds structures that should glide smoothly, physically restricting the joint from achieving full flexion or extension.
Muscle imbalances and surrounding soft tissue tightness also contribute to restricted movement. When the muscles supporting the knee, particularly the quadriceps and hamstrings, are weak or inflexible, they can prevent the joint from reaching its full range. For example, tightness in the posterior capsule or the quadriceps muscle can limit the ability to fully bend the knee.
Active and Passive Movement Techniques
To safely regain mobility, movement techniques are categorized as either active or passive, depending on whether you use your own muscle power or external assistance. Active range of motion exercises use your own muscles to move the joint through its available range without outside help. A simple active technique is the heel slide, performed while lying on your back, where you slide your heel toward your buttocks, bending the knee as far as possible.
Another active technique is the straight leg raise, which helps strengthen the quadriceps muscle, supporting joint stability and movement. These active movements should be slow and controlled, focusing on engaging the muscles through the entire available range. Consistency is more important than intensity, so aim for multiple repetitions throughout the day rather than one strenuous session.
Passive range of motion movements involve using an external force, such as gravity, your hands, or a towel, to assist the joint past the point where your muscles can take it. An effective passive exercise is the assisted heel slide for flexion, where you loop a towel or strap around your foot while sitting or lying down. Gently pull the ends of the towel to increase the knee bend, holding a gentle stretch for five to ten seconds.
For improving extension, a passive stretch involves placing a small rolled towel beneath your ankle while sitting with your heel elevated. Gravity works to gently push the knee into a straighter position, helping to achieve the zero degrees of full extension necessary for walking. Perform all movements slowly and stop immediately if you feel any sharp, sudden, or increasing pain, as this indicates you are pushing the joint too far.
Adjunctive Therapies and Lifestyle Adjustments
Non-exercise therapies can support movement techniques by preparing the tissues and managing inflammation. Applying heat before exercise is beneficial for chronic stiffness, such as that caused by arthritis, because it increases blood flow and helps loosen tight muscles and connective tissues. Heat therapy makes the soft tissues more pliable, allowing for a more effective and comfortable stretch during movement exercises.
Conversely, cold therapy is recommended after exercise or in cases of acute injury, as it constricts blood vessels to reduce swelling and inflammation. Applying a cold pack for 10 to 15 minutes can help calm down any irritation or pain arising from the stretching process. Gentle massage or foam rolling on surrounding muscles, like the hamstrings and quadriceps, can also alleviate tightness restricting joint movement.
Managing body weight plays a significant role in improving knee movement and comfort over the long term. For every pound of excess body weight, the knees bear an additional four pounds of pressure during activities like walking. Weight loss reduces this mechanical stress on the joint cartilage, which can slow the progression of degenerative conditions and allow the joint to move more freely.
When to Seek Professional Guidance
While home exercises are helpful, certain indicators suggest that professional guidance from a healthcare provider or physical therapist is necessary. Seek an assessment if you experience persistent pain that does not improve after several weeks of consistent home exercises, or if the pain suddenly worsens. A professional evaluation is needed if the knee joint is badly swollen, red, or warm to the touch, as these signs can indicate an infection or an underlying inflammatory condition.
Immediate medical attention is required if your knee gives out while walking, locks or catches during movement, or if you cannot bear weight on the leg. A healthcare professional can perform diagnostic imaging, such as X-rays or MRI, to identify structural issues like a meniscus tear or bone spurs that physically block the joint’s movement. They can also tailor a physical therapy program that includes manual therapy and targeted strengthening to address complex or chronic limitations.