Knee flexion is the ability to bend the knee joint. This movement is fundamental for daily activities like sitting down, climbing stairs, or walking with a normal gait. Loss of this motion, often due to scar tissue after surgery, acute injury, or stiffness from arthritis, significantly impairs mobility. Regaining a full range of motion is a primary focus of rehabilitation to ensure the knee can withstand the demands of everyday life and prevent long-term functional issues. This process requires a consistent approach that addresses pain, stiffness, and muscle strength.
Managing Inflammation and Pain Prior to Movement
Preparation is fundamental for safe and effective rehabilitation. Before attempting to push the joint into a deeper bend, use heat therapy to prepare the tissues. Applying heat for 10 to 20 minutes before exercise increases blood flow, which helps relax tight muscles and connective tissues, making them more pliable for stretching.
Distinguishing between tolerable discomfort and sharp pain is important when performing mobility work. Stretching a stiff joint should create a strong pulling or tension sensation, but never sudden, sharp, or stabbing pain. If a movement causes prohibitive pain, immediately back off and consult a healthcare professional, as pushing through sharp pain can cause further tissue damage or inflammation.
After a session aimed at increasing flexion, use cold therapy to manage the inflammatory response to stretching. Applying an ice pack for 20 minutes constricts blood vessels, which reduces swelling and pain around the joint. This combination of heat before movement and ice after helps the joint safely gain range of motion without excessive post-exercise swelling that could cause stiffness to return.
Specific Active and Passive Range of Motion Exercises
To physically increase the angle of the knee bend, a combination of active and passive range of motion (ROM) exercises is necessary. Active ROM uses the muscles around the knee to move the joint without external assistance, helping to re-establish neuromuscular control. A foundational active exercise is the Heel Slide, performed by lying on your back and slowly dragging the heel toward the buttocks. This movement should be controlled and repeated for 10 to 15 repetitions, holding briefly at the point of maximum comfortable flexion, often done two to three times daily.
Passive ROM exercises use an external force—such as gravity, a strap, or the opposite limb—to move the joint beyond what the muscles can achieve alone, providing a deeper, sustained stretch. The Wall Slide is an effective passive exercise where you lie on your back with your feet up the wall and allow the affected heel to slide down, bending the knee until a deep stretch is felt. The unaffected leg can gently press on the shin of the involved leg to provide additional overpressure, which helps remodel scar tissue and increase the end range. This deep stretch is held for 10 to 30 seconds and repeated several times per session.
The Prone Hang is a passive technique that focuses on regaining full extension, which is a necessary precursor to maximizing flexion. This involves lying face-down on a bed or table with the knee hanging off the edge, allowing gravity to gently pull the lower leg downward. The prone hang prevents the knee from adopting a flexed posture, which can stall overall ROM progress.
Integrating New Flexibility with Functional Strength
Achieving a new range of motion through stretching is only the first step; the body must then be able to control and stabilize the joint within this new flexibility. Functional strength training loads the joint and surrounding muscles in a controlled, weight-bearing manner. The goal is to build muscle strength within the full, newly acquired arc of motion, making the flexibility usable during daily activities.
Shallow Squats are a primary exercise for this integration, performed by standing and bending the knees only to a comfortable depth, perhaps 30 to 45 degrees of flexion. The movement focuses on recruiting the quadriceps and gluteal muscles to control the descent and ascent, which reinforces dynamic stability at the joint. As strength improves, the depth of the squat can gradually increase, challenging the knee through greater flexion.
Mini-Lunges and Step-Ups further challenge the joint by introducing single-leg balance and loading the knee through a functional movement pattern. For the Step-Up, the affected leg steps onto a low surface, such as a step no higher than eight inches, and the knee is straightened to lift the body. These exercises require the muscles to work concentrically and eccentrically to manage body weight, which is essential for translating stretching gains into walking and stair climbing.
Recognizing Plateaus and When to Seek Professional Guidance
A plateau occurs when consistent effort no longer yields measurable improvement in range of motion or strength over several weeks. For example, if daily stretching produces no change in the knee’s maximum bend over a 10-day period, the joint may require an external assessment. A physical therapist or physician can assess whether underlying scar tissue or muscle imbalances are the primary limiting factor.
Specific warning signs necessitate immediate professional consultation rather than continued self-management. These symptoms suggest an issue beyond simple stiffness and require a customized assessment:
- A sudden, unexplained increase in swelling that lasts more than 24 hours after light activity.
- A new onset of redness or warmth around the joint, which could indicate infection or a significant inflammatory response.
- A feeling of instability or the inability to bear weight.
- The development of sharp, persistent pain that prevents normal movement.