Unstable Knee – Causes and Management

What You Might Feel – Symptoms (Clinical Presentation)

The primary symptom of knee instability is the sensation of the knee “giving away” or buckling, especially during activities that involve twisting or turning. Other symptoms include:

• Knee pain

• Swelling

• Limited range of motion

• Weakness or difficulty bearing weight on the affected leg

These symptoms are typically worse during physical activities that place strain on the knee joint, such as running, climbing stairs, or even walking on uneven surfaces.

How Doctors Find the Problem? (Diagnosis and Imaging)

Knee instability is diagnosed through a combination of physical examination and imaging tests.

• Physical examination: The orthopedic surgeon assesses the knee’s stability by performing special maneuvers that stress the ligaments and examine the range of motion.

• X-rays: These provide a view of the bones and can help identify fractures or signs of arthritis.

• MRI: An MRI is essential for detecting soft tissue injuries, such as tears in ligaments, the meniscus, or cartilage.

• Arthroscopy: Considered the gold standard, this procedure involves inserting a small camera into the knee joint to directly visualize damage to the ligaments and cartilage.

Classification

Knee instability can be classified based on the location and severity of the ligament damage:

• Anterior Instability: Due to damage to the ACL, lateral capsular, or medial capsular ligaments.

• Posterior Instability: Due to damage to the PCL or arcuate complex.

• Medial Instability: Caused by injuries to the MCL, medial capsular ligament, and occasionally the PCL.

• Lateral Instability: Caused by injuries to the lateral collateral ligament, lateral capsular, or iliotibial band (ITB).

Other Problems That Can Feel Similar (Differential Diagnosis)

Other conditions that can mimic knee instability include:

• Patellar dislocation or subluxation

• Meniscus tears: May cause pain and a feeling of instability, particularly with twisting motions.

• Osteoarthritis: Can cause pain, swelling, and mechanical symptoms that resemble instability.

• Referred pain: Conditions such as hip or lower back issues can sometimes present as knee instability.

Treatment Options

Non-Surgical Care
For mild to moderate knee instability, non-surgical treatments may be effective, including:

• Bracing: To provide support and prevent excessive movement of the knee.

• Rest and ice: To reduce swelling and inflammation.

• Physical therapy: Strengthening the muscles around the knee, particularly the quadriceps, can help stabilize the joint.

• Anti-inflammatory medications: To manage pain and swelling.

Surgical Care
In more severe cases, surgery may be required to repair torn ligaments or other damaged structures. The most common surgical approach is arthroscopic surgery, in which small incisions are made, and a camera is used to guide the repair of the damaged ligaments or meniscus. Rehabilitation following surgery is crucial for regaining strength and mobility.

Recovery and What to Expect After Treatment

Recovery depends on the severity of the injury and the type of treatment. After non-surgical treatment, patients typically experience gradual improvement in knee stability, with most returning to normal activities within 6-8 weeks.

For surgical cases, recovery can take several months, with a structured rehabilitation program that includes physical therapy and gradual reintroduction to physical activities. Full recovery may take up to 6-12 months, depending on the extent of the injury and the success of the surgery.

Possible Risks or Side Effects (Complications)

Complications from knee instability treatment can include:

• Infection (especially after surgery)

• Blood clots: Especially after surgery, patients may be at risk of deep vein thrombosis (DVT).

• Re-injury: The knee may remain vulnerable to further injury if rehabilitation is not followed carefully.

• Chronic instability: In some cases, even after treatment, patients may continue to experience instability if the knee does not heal correctly.

Long-Term Outlook (Prognosis)

The prognosis for knee instability varies. In many cases, proper treatment and rehabilitation can restore knee stability and function. However, untreated or poorly managed knee instability can lead to further damage to the knee joint, including arthritis and ongoing instability.

Out-of-Pocket Costs

Medicare

CPT Code 27380 – Ligament Repair (Collateral Ligaments): $148.14
CPT Code 29888 – ACL Reconstruction: $229.85
CPT Code 29889 – PCL Reconstruction: $290.95
CPT Code 27427 – Multiligament Knee Reconstruction / Capsular/Plica Repair (Stability Procedures): $168.63
CPT Code 27487 – Revision Total Knee Replacement (Instability After TKR): $413.16

Under Medicare, 80% of the approved amount for these procedures is covered once your annual deductible has been met. The remaining 20% is typically the patient’s responsibility. Supplemental insurance plans—such as Medigap, AARP, or Blue Cross Blue Shield—generally cover this 20%, meaning most patients will have little to no out-of-pocket expenses for Medicare-approved surgeries. These supplemental plans work directly with Medicare to ensure full coverage for the procedures.

If you have secondary insurance—such as Employer-Based coverage, TRICARE, or Veterans Health Administration (VHA)—it acts as a secondary payer once Medicare processes the claim. After your deductible is satisfied, these secondary plans may cover any remaining balance, including coinsurance or small residual charges. Secondary plans typically have a modest deductible, usually between $100 and $300, depending on the specific policy and network status.

Workers’ Compensation
If your knee surgery is work-related, Workers’ Compensation will fully cover all treatment-related costs, including surgery, hospitalization, and rehabilitation. You will have no out-of-pocket expenses under an accepted Workers’ Compensation claim.

No-Fault Insurance
If your knee injury requiring surgery is the result of a motor vehicle accident, No-Fault Insurance will cover all medical and surgical expenses, including ligament repairs and total knee replacement revision. The only possible out-of-pocket cost may be a small deductible depending on your individual policy terms.

Example
Tom, a 50-year-old patient with knee instability and a torn ACL, underwent ACL reconstruction (CPT 29888) and later required multiligament knee reconstruction (CPT 27427). His estimated Medicare out-of-pocket costs were $229.85 for the ACL reconstruction and $168.63 for the multiligament procedure. Since Tom had supplemental insurance through Blue Cross Blue Shield, the 20% that Medicare did not cover was fully paid, leaving him with no out-of-pocket expenses for the surgeries.

Frequently Asked Questions (FAQ)

Q. Can knee instability be prevented?
A. While it is not always preventable, strengthening the muscles around the knee and using proper techniques during sports can reduce the risk of injury.

Q. How long will it take to recover from knee instability?
A. Recovery time depends on the severity of the injury and the treatment method. Non-surgical treatments may take a few weeks, while surgical recovery can take 6-12 months.

Q. Is surgery necessary for knee instability?
A. Surgery may be necessary if conservative treatments such as physical therapy and bracing do not provide sufficient relief or if there are significant ligament tears.

Summary and Takeaway

Knee instability is a common and often disabling condition that can impact daily activities. Early diagnosis and appropriate treatment, whether conservative or surgical, are key to managing the condition and improving outcomes. With proper care, most patients can regain stability and resume their regular activities.

Clinical Insight & Recent Findings

A recent study explored the outcomes of in-situ mosaicplasty fixation for treating unstable osteochondritis dissecans (OCD) of the knee in skeletally mature patients. This technique, which involves using autologous osteochondral plugs to stabilize the lesion, demonstrated high healing rates, with MRI scans showing complete healing in 12 out of 13 cases within six months.

The study highlighted that in-situ mosaicplasty offers both mechanical stability and biological augmentation, making it an ideal first-line surgical option for unstable OCD.

Additionally, it showed that the procedure is minimally invasive, with excellent patient-reported outcomes and minimal complications, further validating its use in managing unstable knee conditions. (“Study of in-situ mosaicplasty fixation for unstable knee OCD – See PubMed.“)

Who Performs This Treatment? (Specialists and Team Involved)

Orthopedic surgeons specializing in knee injuries typically perform surgery for knee instability. Physical therapists play a critical role in rehabilitation, while other specialists, such as pain management doctors, may assist in non-surgical management.

When to See a Specialist?

You should see a specialist if you experience knee instability that does not improve with rest or physical therapy, if you have significant knee pain or swelling, or if you are unable to bear weight on the affected leg.

When to Go to the Emergency Room?

Seek emergency care if you experience sudden, severe pain, inability to move the knee, or signs of a blood clot (e.g., swelling, redness, or warmth in the leg). These could indicate serious complications requiring immediate attention.

What Recovery Really Looks Like?

Recovery from knee instability varies depending on the severity of the injury and the chosen treatment. With appropriate care, most patients can return to their normal activities, though full recovery from surgery may take several months.

What Happens If You Ignore It?

Ignoring knee instability can lead to further damage to the knee, including arthritis, chronic pain, and increased risk of future injury. Early intervention is crucial for preventing long-term complications.

How to Prevent It?

Prevention includes strengthening the muscles around the knee, using proper form during physical activities, and wearing supportive gear, especially for athletes or individuals with a history of knee injuries.

Nutrition and Bone or Joint Health

A healthy diet rich in calcium, vitamin D, and protein is essential for maintaining strong bones and joints. Staying hydrated and maintaining a healthy weight can also reduce stress on the knee joint, preventing further instability.

Activity and Lifestyle Modifications

Patients with knee instability should focus on low-impact activities such as swimming or cycling while avoiding high-impact sports or movements that could exacerbate the condition. A physical therapist can recommend specific exercises to improve knee strength and stability.