Osteoarthritis of the Knee

Osteoarthritis (OA) of the knee—also known as degenerative joint disease (DJD)—is the progressive breakdown of the knee joint components over time, and is the most common type of arthritis. This can result from normal wear and tear (primary OA) or occur as the result of a specific knee injury earlier in a person’s life (secondary OA). Other forms affecting the knee include Rheumatoid Arthritis (RA), an autoimmune disease that attacks the synovial membrane, and Post-Traumatic Arthritis, which is the accelerated onset of arthritis following a severe injury to the joint.

While not always symptomatic, osteoarthritis that causes pain or a decrease in function is most common, affecting 22% of individuals over the age of 60.¹ The incidence in women can be almost four times higher than that of men, especially after menopause.² There is currently no cure for arthritis, but there are various conservative and surgical treatment options to manage the condition.

To understand OA, it helps to know the anatomy of the knee joint. The knee is the largest hinge joint in the body and is primarily limited to flexion (bending) and extension (straightening) movements. It’s where the lower end of the femur (thigh bone) meets the upper end of the tibia (shin bone), and sitting in front of their union is the patella (kneecap).

Articular cartilage covers the ends of these bones to create a smooth, slippery surface for them to glide against one another. Additionally, the menisci—two wedge-shaped pieces of fibrocartilage on either side of the knee—create a cushion between the femur and tibia to absorb the shock of weight-bearing activities. The synovial membrane covers the joint surface and provides lubrication to the cartilage. The breakdown of this cartilage and the underlying bone leads to arthritis.

Causes

Over time, repeated weight-bearing activities on the knee can wear down the cartilage in the joint. Excess weight, repetitive high-impact activities, and repeated trauma can speed up this breakdown. As cartilage thins and deteriorates, the protective space between the bones decreases, eventually leading to bone-on-bone contact. This leads to friction, inflammation, pain, and stiffness, which can severely limit range of motion and quality of life. Osteoarthritis usually develops slowly over several years.

While conventional wisdom has pinned the cause of osteoarthritis solely on mechanical “wear and tear,” new research shows that hormonal changes due to obesity can cause widespread inflammatory reactions that attack the joints and accelerate degradation.³ Therefore, patients who suffer from obesity may have a higher risk of osteoarthritis on both a mechanical (weight) and hormonal (chemical) level.

Symptoms

If you are experiencing knee pain, consulting a qualified orthopedic specialist early on can help prevent further deterioration down the road. A proper diagnosis can ensure the right treatment plan going forward. The most common symptoms include:

• Pain that is usually gradual and worsens over time, though it can flare up suddenly following activity.
• Decreased range of motion (ROM) that limits the ability to fully straighten or bend the knee.
• “Barometer knee”—pain that worsens with cold or rainy weather due to changes in barometric pressure.
• “Start-up pain”—stiffness that is worse after long periods of inactivity (like sleeping or sitting) but improves after a few minutes of movement.
• A grinding, clicking, or cracking sensation (called “crepitus”) when moving the knee.
• Feeling as though the knee is going to give out or buckle.

Diagnosing

The diagnostic process begins with a physical examination and a full medical history. During the exam, your orthopedic surgeon will test for tenderness, swelling, stability, and range of motion.

X-rays are the first and often definitive diagnostic imaging test used. They reveal the “joint space”—or lack thereof. A healthy knee has a gap between the bones (filled with cartilage); an arthritic knee shows “bone-on-bone” contact, sometimes along with bone spurs (osteophytes). An MRI or CT scan may be ordered if the surgeon needs to visualize the soft tissue or plan for complex surgery.

Treatments

Conservative Treatment Options

Conservative treatment is the first line of defense and is often successful in managing symptoms.

• Lifestyle modification: Weight loss is crucial. For every pound of weight lost, you remove four pounds of pressure from the knee joint during walking.
• Activity modification: Swapping high-impact activities (running) for low-impact ones (cycling, swimming) preserves the remaining cartilage.
• Physical therapy: Strengthening the quadriceps and hamstrings helps stabilize the knee, taking the burden off the joint surfaces.
• Injections:
  • Corticosteroids: Potent anti-inflammatories for short-term relief.
  • Hyaluronic acid (Viscosupplementation): Gel-like injections that mimic natural joint fluid to lubricate the knee.

Surgical Treatment Options

When conservative treatment fails, surgery may be necessary.

• Total knee replacement (TKR): The damaged cartilage and bone are resurfaced with metal and plastic components. This is the gold standard for end-stage arthritis.
• Partial knee replacement: Only one compartment (medial or lateral) is replaced. This preserves the ACL and PCL ligaments and offers a faster recovery, but is only suitable for specific candidates.
• Osteotomy: The tibia or femur is cut and realignehgytgd to shift weight away from the damaged side of the knee to the healthy side. This is typically reserved for younger, active patients to delay the need for replacement.

1. Clark, K. E., & Jawad, A. S. (2023). Osteoarthritis management: does sex matter? Trends in Urology & Men’s Health, 14(4), 8–12. https://doi.org/10.1002/tre.928.
2. Segal, N. A., Nilges, J. M., & Oo, W. M. (2024). Sex Differences in Osteoarthritis Prevalence, Pain Perception, Physical Function and Therapeutics. Osteoarthritis and Cartilage, 32(9), 1045–1053. https://doi.org/10.1016/j.joca.2024.04.002.
3. King, L. K., March, L., & Anandacoomarasamy, A. (2013). Obesity & osteoarthritis. The Indian journal of medical research, 138(2), 185–193. https://pmc.ncbi.nlm.nih.gov/articles/PMC3788203/.