Various ailments, diseases, and injuries can cause knee pain. Identifying the underlying cause and type of knee pain can help the affected individual and medical practitioners better determine treatment and facilitate recovery. Knee pain can present along with various symptoms and signs.

Swelling

The cause of swelling of the knee is usually fluid around the joint limiting movement and flexibility. The skin around the knee becomes tight and stretched, tender to the touch, and pink or red. The swelling causes pain in the knee, and the buildup of fluid may make it difficult to put weight on that knee. The injured individual may have trouble bending or straightening the knee completely, and the kneecap may appear puffed up. Comparing the painful knee to the uninjured one can help determine the extent of the inflammation.

Stiffness

A stiff knee can result from an injury or a medical condition. Although the entire knee may feel stiff, most people feel this sensation under the kneecap or inside the joint, which makes topical treatment difficult. Stiff knees are common in people with arthritis and often present along with knee pain, numbness, or tingling.

Redness and Warmth

Discoloration of the skin and a warm feeling are sure signs of knee inflammation or injury. These often develop as the body is attempting to heal and protect the area as it does so. Arthritis, bursitis (inflammation of the small, fluid-filled sacs that cushion the bones), fractures, and the stretch or tear of muscles are all possible causes of these signs. If the redness and warmth persist for more than a few days or worsen rather than improve, it is best to see a doctor.

Weakness

The knees carry a lot of body weight and take considerable impact, so injuries are not surprising. Weak knees can lead to knee strain or chronic pain, which results in simply walking and standing taking a toll on daily life. People over the age of 70 are more susceptible to weak knees, but the issue can affect people of any age, especially if one has a pre-existing illness or injury. Exercise can help strengthen the muscles around the knee but always check with a doctor before adopting a new workout routine.

Popping and Crunching Noises

Crepitus or noisy joints usually falls into one of three categories. Pain-free popping is when a joint makes a noise unaccompanied by any pain or discomfort. This could be due to gas bubbles bursting or stretched tendons or ligaments snapping over a bony lump. Noisy joints are more common in the elderly because the cartilage wears as part of the aging process, and the bony surfaces rub against each other. Painful popping often occurs at the time of injury and most likely indicates a damaged or torn ligament in the knee from twisting suddenly.

Inability to Fully Extend

Swelling and pain may be the obvious indicators of knee problems, but the root of the problem is likely much deeper. Being unable to fully straighten the leg, along with significant knee pain and inflammation, can point to a serious knee injury. A tear of the anterior cruciate ligament (ACL) is one of the most common knee injuries. A meniscus tear, where a torn piece of the meniscus flips into the knee joint, will make it difficult to straighten the knee. Tendon injuries to the quadriceps muscle or the patella (the kneecap) will also affect one’s ability to straighten the knee.

Knee Lock

Knee lock occurs when the knee seems to be locked into place, unable to bend or straighten. A knee lock can be either a true knee lock or a pseudo knee lock. True knee locking is caused by a blockage — for example, a torn cartilage, a chip fracture or a meniscus tear. If this is the case, the individual may need surgery to remove the blockage. In the case of pseudo knee locking, there is no physical blockage, but rather a muscle spasm triggered by pain in the knee. A pseudo-lock is much more common, and a physician can examine the area to determine the cause. In most instances, painkillers can reduce pain and inflammation. Physical therapy can strengthen the knee to prevent future issues and improve mobility in the joint.

Visible Deformity

Visible deformity of the knee can happen as a result of many factors and events, including rheumatoid arthritis, osteoarthritis, cancer in the cartilage or bone, osteomyelitis (an infection of the bones), or trauma. The knees face considerable stress every day from repetitive movement, sports, stress from carrying excess body weight, or underlying injury or medical conditions and diseases. The deformity is usually caused by swelling, though breaks and dislocations can also cause visible changes.

Buckling

Many people have experienced a buckling knee or the feeling of the joint giving out beneath them. Knee buckling is often caused by knee injuries from high-impact sports or existing joint conditions such as osteoarthritis. In other cases, nerve damage may cause knee instability. Weakness and buckling along with neurological symptoms may suggest multiple sclerosis.

Difficulty Climbing Stairs

Climbings stairs places two to three times the body’s weight on the knees, and the kneecap takes the majority of this excess pressure. Difficulty climbing stairs or lifting oneself out of a chair often relates to a problem with the patella and how it moves as the body rises. The back of the patella is lined with a thick layer of cartilage. If an accident or medical condition damage this cartilage, the injured individual will likely have problems with repetitive activities such as ascending stairs.