Knee

Knee Osteoarthritis

Knee osteoarthritis (OA) is the most common joint disease in the United States, affecting an estimated 14 million Americans and representing the leading cause of chronic disability in adults over 50. At Maryland Orthopedic Specialists, our fellowship-trained orthopaedic surgeons and non-operative sports medicine physicians use a structured treatment ladder — beginning with the most conservative, evidence-backed interventions — to help patients maintain function, reduce pain, and delay or, when appropriate, proceed to surgical replacement.

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What is knee osteoarthritis?

Knee osteoarthritis is the progressive wearing away of the articular cartilage that cushions the knee joint, causing pain, stiffness, and swelling that worsen with activity. It is the leading cause of disability in adults over 65 and affects all three compartments of the knee — medial, lateral, and patellofemoral. Treatment ranges from physical therapy and injections to surgery.

Osteoarthritis is a progressive disease of the entire joint organ — not simply "wear and tear" of cartilage. It involves articular cartilage loss, subchondral bone remodeling (sclerosis, cyst formation, osteophyte formation), synovial inflammation, and periarticular muscle weakness. The knee has three distinct compartments, each susceptible to isolated or combined involvement:

Medial tibiofemoral: Most common; varus deformity ("bow-legged")
Lateral tibiofemoral: Less common; valgus deformity ("knock-kneed")
Patellofemoral: Anterior knee pain; often coexists with tibiofemoral OA

Kellgren-Lawrence (KL) Grading is the standard radiographic classification:

Grade 0 — Normal
Grade 1 — Doubtful narrowing; possible osteophytes
Grade 2 — Definite osteophytes; possible joint-space narrowing
Grade 3 — Moderate narrowing; multiple osteophytes; subchondral sclerosis
Grade 4 — Severe narrowing; bone-on-bone contact; deformity

Risk factors include age > 50, female sex, obesity (the most modifiable factor), prior knee injury, quadriceps weakness, and genetic predisposition.

Treatment options

Treatment follows a structured progression from activity modification and physical therapy through injection management and ultimately surgical reconstruction, guided by symptom severity, functional limitations, and radiographic grade.

Non-Operative Management

The foundation of non-operative care is activity modification, targeted exercise, and judicious use of anti-inflammatory medications. Low-impact aerobic activity — cycling, swimming, and aquatic therapy — maintains cardiovascular fitness and quadriceps strength without the impact loading of running or court sports. Weight management is critically important: each pound of body weight lost reduces knee joint load by approximately four pounds during walking, and a 5 to 10 percent reduction in body weight produces clinically meaningful pain relief in most patients. Physical therapy focuses on quadriceps and hip abductor strengthening to reduce medial compartment load, neuromuscular retraining for proprioception, and gait optimization. An unloader brace effectively shifts load from the affected compartment in unicompartmental disease; patellofemoral bracing addresses isolated anterior knee pain. Ice applied for 15 to 20 minutes after activity reliably reduces inflammatory flares and is one of the simplest and most underutilized tools in knee OA management. Topical NSAIDs (diclofenac gel) are first-line pharmacological therapy — particularly in patients over 65 or with gastrointestinal risk — because they deliver anti-inflammatory effect to the joint with minimal systemic absorption. Oral NSAIDs provide more robust systemic relief for patients without contraindications. Acetaminophen and duloxetine are adjunctive options, with duloxetine particularly useful when central sensitization contributes to the pain picture.

Corticosteroid Injection

Intra-articular corticosteroid injection (typically triamcinolone or methylprednisolone) provides reliable short-term pain relief within 1 to 2 weeks, with effects lasting 4 to 8 weeks on average. It is most useful for managing acute inflammatory flares, reducing pain before starting physical therapy, or bridging a patient ahead of a planned procedure. Ultrasound guidance improves accuracy and is used routinely at MOS. Injections can be repeated, but we generally limit frequency to 3 to 4 per year given evidence of accelerated cartilage degradation with overuse.

Hyaluronic Acid (Viscosupplementation)

Hyaluronic acid injection restores lubrication and cushioning to the knee by supplementing the depleted synovial fluid of the arthritic joint. Given as a single injection or a series of 3 to 5 weekly injections depending on the product used, onset of relief is gradual over 4 to 8 weeks but duration extends to 3 to 6 months in appropriately selected patients. Best suited for mild-to-moderate osteoarthritis (KL Grade 1 to 3) in patients who prefer to avoid or have not responded adequately to corticosteroid. Less effective in severe bone-on-bone disease.

PRP (Platelet-Rich Plasma)

PRP is drawn from the patient's own blood, concentrated at the time of the visit, and injected into the knee joint. Unlike corticosteroid, PRP works biologically — delivering growth factors that modulate inflammation and may support cartilage health. A series of 1 to 3 injections spaced 4 to 6 weeks apart is typical. Onset of relief is slower than corticosteroid (4 to 8 weeks) but duration is longer, with studies demonstrating superiority over corticosteroid and viscosupplementation at 6 and 12 months in KL Grade 1 to 3 disease. Best suited for patients with mild-to-moderate osteoarthritis who want a longer-lasting, non-steroidal option. PRP is not currently covered by most insurance carriers.

Surgical Procedure

Total Knee Replacement

Complete resurfacing of the knee joint — femur, tibia, and patella — with metal and polyethylene implants to eliminate arthritis pain and restore mechanical alignment. Performed at a hospital facility with full inpatient support services.

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Partial Knee Replacement (Unicompartmental)

Resurfacing of only the damaged compartment of the knee — medial, lateral, or patellofemoral — while preserving the intact ligaments and articular cartilage in the remaining healthy compartments.

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Frequently Asked Questions

Can knee OA be reversed?

Articular cartilage has limited regenerative capacity, so structural changes of OA are not reversed by current treatments. However, symptoms can be substantially improved, and disease progression can be slowed with weight loss, exercise, and appropriate interventions.

At what KL grade should I consider surgery?

There is no absolute radiographic threshold. Surgery is considered when symptoms are severe enough to significantly limit daily function despite at least 3–6 months of comprehensive non-operative management. KL Grade 4 disease with bone-on-bone contact and deformity that fails conservative care is the typical indication for TKR.

Is PRP covered by insurance?

PRP is not currently covered by most insurance carriers for knee OA. Our team will discuss out-of-pocket costs and expected outcomes at your consultation.

How long does a knee replacement last?

Modern implants demonstrate > 90% survivorship at 15–20 years in registry data, with continued improvement in outcomes as implant design and bearing surfaces advance.

Are there exercises I should be doing to slow the progression of my knee arthritis?

Regular low-impact exercise is one of the most effective ways to manage knee osteoarthritis — it reduces pain, improves function, and can slow structural progression. Recommended activities include cycling, swimming, elliptical training, and targeted quadriceps and hip strengthening, which reduce the load transmitted through the knee joint. High-impact activities such as running on hard surfaces may be tolerated in mild arthritis but should be guided by your symptoms. At MOS, your care team can connect you with physical therapy to design an individualized exercise program that balances joint protection with maintaining your activity level.