The Clinician’s Guide to Assessing Knee Osteoarthritis

Many people believe knee Osteoarthritis (OA) to be a “wear-and-tear” process of the knee’s cartilage that occurs with aging – as physios, this is a common narrative we hear from our patients. However, research has revealed that osteoarthritis is more complex than just cartilage “wear and tear”. Knee OA can involve multiple pathophysiological changes such as cartilage degradation, bony adaptations, meniscal damage, and synovial inflammation. Further, we now know that knee OA is a clinical diagnosis (rather than being solely based on imaging findings), which means our assessment skills as physiotherapists are crucial in the appropriate diagnosis and management of knee OA. In this blog, we’ll walk through expert physiotherapist Allison Ezzat’s Practical on knee OA assessment.

If you’d like to see exactly how expert physio Allison Ezzat manages knee OA, watch her full Practical HERE. With Practicals, you can be a fly on the wall and see exactly how top experts assess and treat specific conditions – so you can become a better clinician, faster. Learn more here.

Subjective examination

Traditionally, knee OA was diagnosed with X-ray imaging; however, research has demonstrated poor correlations between imaging findings and patient symptoms. Instead, we now rely on a combination of risk factors, patient symptoms, and clinical objective findings. Common risk factors include:

• Advanced age
• Being female
• Family history of OA
• History of a prior knee injury
• History of chronic overload (e.g., elite runners, farmers)
• Being overweight
• Physical inactivity
• Quadriceps muscle weakness

Common symptoms to look out for include pain with weight-bearing activities, feelings of instability or looseness, crepitus, morning stiffness, and anteromedial knee pain. To aid in your assessment, consider tools such as the National Institute for Health and Care Excellence (NICE) Criteria and the Knee Injury and Osteoarthritis Outcome Score (KOOS), which are used for diagnosis and outcome tracking, respectively.

In addition to clinically diagnosing knee OA, we also want to screen for red flags and refer out if needed. Our subjective assessment should enable us a thorough understanding of patient beliefs about OA, their expectations, and functional goals.

Objective examination

A combination of functional assessments, standardised tests and impairment testing help us understand the patient’s functional capacity. Functional assessments provide a qualitative assessment of movement, while standardised tests can be compared against normative data and used to track the patient’s progress.

Functional assessments

The first functional assessment to observe is the patient’s gait, where we look for major deviations (e.g., the Trendelenburg gait pattern) and perform a gross assessment of dynamic balance. Next, we move into the step-up. When assessing the step-up, we want to compare left and right lower extremities, looking at perceived exertion, pain and biomechanics. Lastly, we observe how the patient performs a sit-to-stand, assessing movement mechanics, pain and perceived exertion.

Standardised tests

After gaining a qualitative understanding of our patient’s functional abilities, we will quantify their movement capacity with standardised tests. Firstly, we’ll use the 40-Meter Walk Test (40MWT), which measures walking speed over short distances. See Allison demonstrate this test in the below video taken from her Practical:

The next assessment is the 30-second sit-to-stand (30sSTS), which measures gross lower extremity strength and dynamic balance. The patient performs as many sit-to-stands as possible in 30 seconds with their arms crossed across their chest to reduce upper-limb assistance. If the patient must use their upper extremities for support, we record their score, but this is considered an “adapted” score and cannot be directly compared to normative data.

Lastly, for higher level patients who max out the previous standardised tests, we can perform a hop for distance test in which the patient performs three separate hops for distance and the best score is recorded.

Range Of Motion (ROM) assessment

When assessing ROM, we should include knee flexion and extension, as well as the rest of the lower extremity (i.e., hip and ankle). Knee flexion is commonly limited in patients with knee OA, and this can lead to difficulty with functional activities such as getting out of a chair.

Strength testing

At a minimum, this should involve assessing knee flexion, knee extension, and hip abduction. These are ideally performed using a hand-held dynamometer; however, a 10-repetition maximum with an ankle weight or resistance band can be performed if a dynamometer is not readily available. Additionally, a 10-repetition maximum single-leg press may be performed to assess strength changes over time.

Special tests

The main special tests we will consider are the varus and valgus stress tests, as well as McMurray’s and Thessaly’s tests. Note that the meniscal tests – McMurray’s and Thessaly’s – are only indicated if the patient describes symptoms consistent with meniscal pathology, such as locking, catching, or their knee “giving way”.

Joint mobility and palpation

This should be assessed to understand how the knee has been affected by OA. For joint mobility, we’ll assess both patellofemoral and tibiofemoral joint mobility. To assess patellofemoral joint mobility, we’ll perform patellar glides, primarily focusing on medial and inferior glides. To assess tibiofemoral joint mobility, we’ll perform anterior and posterior glides. Note that there are multiple ways to describe and perform these glides (e.g., an anterior tibial glide is a relative posterior femoral glide). Allison demonstrates how she assesses joint mobility in the below video taken from her Practical:

For palpation, check for tenderness around the whole knee joint, paying special attention to three areas: the patellofemoral joint, medial knee structures, and lateral knee structures. At the patella, we’ll check for tenderness on the patella and the patellar tendon. To assess medial knee joint structures, have the patient in hook lying and palpate the medial joint line, medial collateral ligament, and pes anserine. To assess lateral knee joint structures, ideally have the patient’s leg in a “figure 4” position (if they can achieve/tolerate this) and palpate the lateral joint line, lateral collateral ligament, iliotibial band, and fibular head.

Related to palpation, it’s important to assess gross joint swelling using the sweep/brush test, which Allison demonstrates in this snippet from her Practical:

Wrapping up

Diagnosis of knee OA should be rooted in the combination of assessment of risk factors, patient symptoms, and a comprehensive objective exam. Your assessment should also aim to gain a thorough understanding of patient beliefs and goals which may influence treatment planning. This approach not only ensures we are assessing/treating more than just the knee, but also demonstrates our unique value in the primary care of osteoarthritis. As the incidence of knee OA rises worldwide, we can play a crucial role in managing this condition and helping our patients live fuller, more enjoyable lives.

To see exactly how a master physio manages persistent low back, check out Allison Ezzat’s full Practical HERE.