A Multifaceted Presentation of Knee Pain in a 40-Year-Old Woman

Jenny McConnell, Darren A. Rivett

Subjective History

Karina, a 40-year-old female patient, presented for treatment of bilateral knee pain (Fig. 6.1). The pain started in her left knee 3 years earlier after a period of intensive running.

Past History of Complaint

Three months after her pain had commenced, she consulted a sports physician, who prescribed Mobic (a non-steroidal anti-inflammatory drug [NSAID]) and referred her for physiotherapy after obtaining a magnetic resonance imaging (MRI) scan of her left knee. The MRI scan showed that Karina had changes, including chondromalacia patellae in the lateral patellar articular facet and mild Hoffa’s fat-pad change, suggesting patellar mal-tracking or fat-pad impingement, as well as a 5-mm undisplaced, chondral flap of the posterior inner medial femoral condyle. Because there was inflammation in the fat pad, the sports physician administered a corticosteroid injection into the fat pad of her left knee, which initially provided some relief.

The previous physiotherapy program undertaken by Karina consisted of soft tissue massage, taping her knee across the patella and gluteal and quadriceps exercises involving clam exercises, squats and lunges, as well as hamstrings stretches. Three months after commencing physiotherapy, she returned to the sports physician because her right knee was now painful. The sports physician instructed her to cease taking the Mobic because it did not seem to be helping. The physiotherapist had informed the sports physician that Karina was now able to descend stairs without pain and that there was improvement as measured on biofeedback, with the medial quadriceps almost equal to the lateral quadriceps. However, the physiotherapist also noted that Karina was feeling frustrated at her lack of progress because she was still not back to running, so she was getting quite depressed.

The sports physician suggested Karina stop physiotherapy, increase her walking, start swimming but avoid breaststroke and participate in gym activities, as long as there was no bent-knee work. He also suggested that she purchase the Explain Pain (Butler and Moseley, 2003) book online, feeling that she was developing a degree of ‘pain syndrome around her knees’, and this approach might help direct her attention away from her knees. He emphasized to her that the MRI scan did not show any significant pathology and that her present discomfort did not mean that she was further damaging her knee.

Twelve months after her left knee pain commenced, Karina experienced left-sided back pain, with intermittent non-specific referral of pain into the left thigh (Fig. 6.1). She believed that she had ruptured a disc, although she did not have a scan. She received physiotherapy involving back and sacro-iliac joint mobilization, as well as transversus abdominis exercises for the back problem, but she was unsure whether physiotherapy helped her back or whether the ‘disc problem’ resolved itself with time because the symptoms gradually became more manageable. Her back was still intermittently problematic depending on what she was doing.

Present History of Complaint

Before her initial examination at our clinic, Karina was sent for a new MRI scan of her left knee (Figs 6.2 and 6.3), which again showed low-grade Hoffa’s fat-pad oedema, in keeping with changes resulting in patellar mal-tracking, patellar alta with a mildly flattened trochlear groove (interestingly enough, this was not commented upon in the first MRI report), and increased signal in the patellar articular cartilage. When asked during the history why she had come for physiotherapy this time, she stated that she had complex regional pain syndrome (CRPS). She had been attending the pain clinic at the nearby hospital for the last 2 years, where the psychiatrist had prescribed Pristiq (desvenlafaxine), which is a selective serotonin and norepinephrine reuptake inhibitor designed to rebalance the brain’s chemicals in people with major depressive disorders.

Fig. 6.2 MRI scans of the left knee. The axial view (left) demonstrates chondromalacia, and the sagittal view, medial side (middle) and lateral side (right), demonstrates inflammation of the infrapatellar fat pad and patellar alta.

Fig. 6.3 MRI scans of the left knee demonstrating a 5-mm undisplaced chondral flap of the posterior inner medial femoral condyle (unchanged from previous scans).

Karina also volunteered that her 3-year-old nephew had been diagnosed with leukaemia but was now in remission. This diagnosis had caused significant distress and upheaval in her family. Her stress release was running, which she was no longer able to do because of her knee pain. She felt that her inability to run and the strain of her nephew’s diagnosis might have contributed to her emotional state of not being able to cope with her knee problems.

Fig. 6.4 Dye’s (1996) model of homeostasis and envelope of function illustrating the effect of intensity and frequency of load on joints. (Reproduced with permission from Springer Healthcare Ltd.)

Reasoning Question:

1. Karina presented to you with a previous history of unilateral knee pain, which had become bilateral by the time of your first consultation. She also reported a prior episode of low back pain, and she still had some intermittent back pain at presentation. What were your early thoughts about the mechanisms involved in these symptomatic presentations?

Answer to Reasoning Question:

Karina initially experienced unilateral knee pain because she had either increased the frequency of her running with not enough time for recovery or because she had increased the intensity of her running and was running steeper gradients. She was therefore outside her envelope of function, so she had breached the threshold of what her knee could cope with, as her quadriceps muscle had either fatigued or was not strong enough eccentrically for descending steep hills. Her inner-range quadriceps control was likely compromised, so she hyperextended her knee, which inflamed the infrapatellar (Hoffa’s) fat pad.

The infrapatellar fat pad is highly innervated and when inflamed causes quadriceps inhibition (Dragoo et al., 2012; Bennell et al., 2004). During walking, 0.5× body weight goes through the knee, but with stairs, this increases to 3–4× body weight (Reilly and Martens, 1972), so if the quadriceps is inhibited, and the demand through the joint increases, the patient will offload the painful knee by solely using the other knee for stair ascent and descent. This can cause an overloading of the other knee, and hence it will result in that knee being outside its envelope of function, resulting in bilateral knee pain.

When a patient has bilateral knee pain, she will be more reluctant to flex her knees when she is lifting objects or picking things off the floor, so she will bend her back more, which will put increased pressure on her lumbar spine and hence predispose her to back strain or injury. Interestingly, it has been established in feline spines that a 20-minute bout of sustained flexion or 20-minute bout of intermittent flexion and extension causes a hundred-fold increase in neutrophil density in the supraspinous ligament 7 hours later, indicative of an acute soft tissue inflammation. This is accompanied by a reflexive increase in multifidus activity (Solomonow et al., 2003a, 2003b, 2008).

When the quadriceps is weak, a patient may compensate by using the hamstrings and gastrocnemius muscles to stabilize the knee (Besier et al., 2009; Henriksen et al., 2007). With the hamstrings stabilizing the knee, the hamstrings become tighter, and a tight hamstrings muscle is associated with an increased incidence of low back pain (Feldman et al., 2001). Patients with low back pain also often have a decrease in gluteus maximus and medius activity (Nadler et al., 2001; Nelson Wong et al., 2008). Pain and the accompanying muscle activation changes can contribute greatly to an alteration in the patient’s gait pattern and therefore loading through her joints. She will likely continue to experience low back pain and knee pain unless these muscle imbalances are addressed.

Reasoning Question:

2. The sports physician initially administered Mobic and a cortisone injection into the fat pad of the patient’s left knee, which gave some short-term relief. What were your thoughts about this, and how relevant did you think the MRI findings were in this case?

Answer to Reasoning Question:

MRI changes of chondromalacia patellae are common, even in asymptomatic individuals, and do not cause pain. The 5-mm chondral flap of the posterior inner medial femoral condyle could cause symptoms of locking if it were displaced, but it would not cause pain, and because the flap was undisplaced, there was no need for any surgical intervention.

The sports physician addressed the inflammatory changes in the infrapatellar fat pad evident on the MRI scan by performing a cortisone injection. A targeted ultrasound-guided cortisone injection into the fat pad can provide pain relief; however, the outcome from the injection is not always consistent, particularly if the cortisone does not reach the area of inflammation in the fat pad. Mobic, an NSAID, is effective if there is a knee joint effusion but is generally not effective for an inflamed fat pad.

The MRI finding of an inflamed fat pad is very significant to the case because it informs us that the quadriceps will continue to be inhibited while the fat pad is inflamed. The knowledge that the fat pad is inflamed should guide our rehabilitation so that we do not give exercises or advice that will further compromise the fat pad. For example, straight leg raises and freestyle kicking in swimming are both activities that will further aggravate the fat pad.

Reasoning Question:

3. If you had been the treating physiotherapist at the initial presentation, what would have been the direction of your treatment?

Answer to Reasoning Question:

It is crucial as a treating clinician, once you have listened to the patient’s history, to give the patient some knowledge about why he or she has pain, where the pain is coming from, and the expected length of time it may take for recovery. Knowledge is power, and it is our responsibility to empower patients to manage their problems and to emphasize that musculoskeletal problems are managed, not cured.

Explaining Dye’s (1996) model of homeostasis and envelope of function (Fig. 6.4) helps the patient to have an idea as to why her knee pain started. Informing the patient about the loading through the knee with activities is important, as is discussing with the patient the effect of pain and fear of pain on quadriceps muscle activity.

Initially, the patient would have been asked to stand in front of the mirror to observe her lower limb alignment – for example, does she have pronated feet or hyperextending knees or internally rotated femurs? While still in front of the mirror, the patient would then be asked to watch her knee as she steps down from a step to see if she has a dynamic knee valgus (or medial knee collapse), and the implications of this abnormal loading of her knee would be discussed with her. Once on the plinth, she would be asked to palpate her infrapatellar fat pad to determine its size and compare it with the opposite leg. She would be able to see that it is enlarged compared with the other leg. It would be explained to the patient that the infrapatellar fat pad has a large number of nerve fibres, so when it is inflamed, it causes a great deal of pain. This pain turns the quadriceps muscle off, and if the quadriceps is turned off, she will feel more pain, which in turn causes fear of pain, which then results in an inhibition of the medial quadriceps causing a mal-tracking of the kneecap, causing more knee pain and so forth. It can be summarized for the patient as follows:

Increased loading through the knee (0.5× body weight through knee when walking; 3–4× body weight on stairs; 7–8× body weight during squatting; 8–10× body weight when running on a level surface) or rapid straightening of the knee ⇨ inflamed fat pad ⇨ knee pain ⇨ ⇩ quadriceps activity ⇨ more knee pain ⇨ fear of pain ⇨ ⇩ inside quadriceps activity ⇨ mal-tracking of the kneecap ⇨ more knee pain ⇨ further ⇩ quadriceps activity ⇨ ⇧ hamstring and calf muscle activity ⇨ ⇩ gluteal muscle activity ⇨ ⇧ limping which may ⇨ low back pain(⇨, leads to; ⇩, decrease in; ⇧, increase in; ×, times).

Initially, the need for improved recruitment of the lower limb muscles is emphasized because strengthening for activities such as running takes a while. So until she is able to do the activity pain-free, it is advisable for the patient not to participate in that activity.

In summary, the more knowledge patients have after the initial examination, the more empowered they are and more on board they are with your treatment.

Clinical Reasoning Commentary:

An understanding of the importance of the strategy of ‘reasoning about teaching’ (see Chapter 1) is evident in this response – that is, reasoning associated with the planning, execution and evaluation of individualized and context-sensitive teaching. In this case, the importance of education for conceptual understanding (e.g. musculoskeletal diagnosis, pain), for physical performance (e.g. rehabilitative exercise, postural correction) and for behavioural change (e.g. running) in patient management is discussed. By enhancing the patient’s knowledge about her problem and how to ‘self-manage’ it, she is empowered to increasingly take control of her situation and minimize the impact on her lifestyle. Education to improve understanding can lead to a decrease in patient fear, greater compliance and a concurrent improvement in pain experienced and movement impairments. Musculoskeletal clinicians require significant skills in teaching patients, an aspect of their formal education which is often only minimally addressed.

Physical Examination

Karina was shown in front of a full-length mirror what was being looked for in the examination (flat feet, puffy looking knees, knees that looked at each other when she put her legs together and straightened out when she squeezed her gluteals) and informed that she had inherited her less-than-ideal anatomy from her parents. She presented with internally rotated femurs (Fig. 6.5), pronated feet and enlarged infrapatellar fat pads, with the left worse than the right. She locked her knees back into extension during walking, and although she had an enlarged fat pad on the left, walking was pain-free. Slight pain (measured on a visual analogue scale [VAS] 3/10) was reproduced going down stairs.